Tectonic Processes and Metallogeny along the Tethyan Mountain Ranges of the Middle East and South Asia (Oman, Himalaya, Karakoram, Tibet, Myanmar, Thailand, Malaysia)

©2016 Society of Economic Geologists, Inc.
Special Publication 19, pp. 301–327
Chapter 12
Tectonic Processes and Metallogeny along the
Tethyan Mountain Ranges of the Middle East and South Asia
(Oman, Himalaya, Karakoram, Tibet, Myanmar, Thailand, Malaysia)
Michael P. Searle,† Laurence J. Robb, and Nicholas J. Gardiner*
Department of Earth Sciences, Oxford University, South Parks Road, Oxford OX1 3AN, United Kingdom
Abstract
The genesis of mineral deposits has been widely linked to specific tectonic settings, but has less frequently
been linked to tectonic processes. Understanding processes of oceanic and continental collision tectonics is
crucial to understanding key factors leading to the genesis of magmatic-, metamorphic-, hydrothermal-, and
sedimentary-related mineral deposits. Geologic studies of most ore deposits typically focus on the final stages of
concentration and emplacement. The ultimate source (mantle, lower crust, upper crust) of mineral deposits in
many cases remains more cryptic. Uniquely, along the Tethyan collision zones of Asia, every stage of the conver-
gence process can be studied from the initial oceanic settings where ophiolite complexes were formed, through
subduction zone and island-arc settings with ultrahigh- to high-pressure metamorphism, to the continental col-
lision settings of the Himalaya, and advanced, long-lived collisional settings such as Afghanistan, the Karakoram
Ranges, and the Tibetan plateau. The India-Asia collision closed the intervening Neotethys ocean at ~50 Ma
and resulted in the formation of the Himalayan mountain ranges, and increased crustal thickening, metamor-
phism, deformation, and uplift of the Karakoram-Hindu Kush ranges, Tibetan plateau, and older collision zones
across central Asia. Metallogenesis in oceanic crust (hydrothermal Cu-Au; Fe, Mn nodules) and mantle (Cr, Ni,
Pt) can be deduced from ophiolite complexes preserved around the Arabia/India-Asia collision (Oman, Ladakh,
South Tibet, Myanmar, Andaman Islands). Tectonic-metallogenic processes in island arcs and ancient subduc-
tion complexes (VMS Cu-Zn-Pb) can be deduced from studies in the Dras-Kohistan arc (Pakistan) and the
various arc complexes along the Myanmar-Andaman segment of the collision zone. Metallogenesis of Andean-
type margins (Cu-Au-Mo porphyry; epithermal Au-Ag) can be seen along the Jurassic-Eocene Transhimalayan
ranges of Pakistan, Ladakh, South Tibet, and Myanmar. Large porphyry Cu deposits in Tibet are related to
both precollisional calc-alkaline granites and postcollisional alkaline adakite-like intrusions. Metallogenesis of
continent-continent collision zones is prominent along the Myanmar-Thailand-Malaysia Sn-W granite belts,
but less common along the Himalaya. The Mogok metamorphic belt of Myanmar is known for its gemstones
associated with regional high-temperature metamorphism (ruby, spinel, sapphire, etc). In Myanmar it is likely
that extensive alkaline magmatism has contributed extra heat during the formation of high-temperature meta-
morphism. This paper attempts to link metallogeny of the Himalaya-Karakoram-Tibet and Myanmar collision
zone to tectonic processes derived from multidisciplinary geologic studies.
Introduction
Mineral deposits have traditionally been linked to specific tec-
tonic settings (e.g., Barley and Groves, 1992; Kerrich et al.,
2005; Groves and Bierlein, 2007; Bierlein et al., 2009; Hou
and Cook, 2009; Richards, 2015) but the origins and concen-
tration processes of the metals contained within them are less
well known. In many cases this is because the ore-forming
processes that are associated with many mineral deposits
take place at the magmatic-hydrothermal stage, are typically
emplaced at high structural levels, and thus are commonly
wholly or partly eroded. Other deposits are entirely epigen-
etic and their relationship to metal source, heat production,
and fluid flow may be less clear. It is only rare occurrences
of deep magmatic intrusions (e.g., Bushveld, Skaergaard) or
obducted ophiolite complexes (e.g., Oman) where the origi-
nal mantle or crustal processes may be directly deduced from
the preserved geology. Classic porphyry Cu-Au-Mo deposits,
and also granite-hosted Sn-W deposits of Andean-type oro-
genic belts are relatively well understood in terms of their
formational processes, but their metal specificity is not always
obvious. A range of other mineral deposit types, including
sediment-hosted base and precious metal ores, and “oro-
genic” Au deposits, are broadly synchronous with orogenic
events, but their detailed link to tectonic processes is likewise
poorly understood. In this paper we review the broad tectonic
evolution and setting of the multifacetted Tethyan orogenic
belt and provide a brief overview of the metallogeny of the
belt in terms of tectonic processes.
Rifting of the southern Gondwana supercontinent (Africa,
Arabia, India) from the northern Laurasia supercontinent
(Europe, northern Asia) resulted in opening of the Tethyan
ocean, an east-west seaway that spanned the entire globe
(Scotese, 2004). The northern tract, termed Paleo-Tethys,
rifted during the Devonian and closed diachronously during
the Triassic and Jurassic (the Indosinian orogeny in SE Asia).
A prominent Permo-Triassic island-arc terrane, the Yidun arc,
extends across Tibet for over 1,000 km (Deng et al., 2014).
301
† Corresponding author: e-mail, mike.searle@earth.ox.ac.uk
*Present address: Centre for Exploration Targeting–Curtin Node, Depart-
ment of Applied Geology, Western Australian School of Mines, Curtin
University, Perth, WA 6102, Australia.

302 SEARLE ET AL.
The Paleo-Tethyan suture zone runs across central Tibet (e.g.,
the Bangong-Nujiang suture; Kapp et al., 2007; Deng et al.,
2014), around the East Himalayan syntaxis, and extends south
through Myanmar and Thailand to Malayasia (e.g., the Ben-
tong-Raub suture; Metcalfe, 2000, 2011; Sone and Metcalfe,
2008). Several distinct continental terranes south of the main
Paleo-Tethyan suture are termed the Cimmerian continents
(Sengör et al., 1993).
The southern tract of Tethys, termed Neotethys, marks the
most recent collision between Gondwana-derived microcon-
tinents and Eurasia. Along the Alpine-Zagros-Oman segment,
Neotethys rifted during the Early Permian with establishment
of a stable carbonate-dominated passive continental margin
(the host rocks to the vast Middle Eastern oil resources in
Permian to Cenomanian reservoirs), and closed diachronously
during the Cenozoic era. Early stages of the collision occurred
along the Zagros Mountains in southwestern Iran with large-
scale folding showing around 100 km of crustal shortening
(Blanc et al., 2003). Two localities along the Alpine-Himala-
yan belt show remnant pieces of Neotethys where continental
collision has yet to occur (NE Mediterranean and the Gulf of
Oman).
In this paper we review the tectonic processes involved in
the formation and evolution of the Tethyan margin around
the Arabian and Indian plates (Fig. 1) along the mountain
ranges of Oman, Pakistan, India, Nepal, South Tibet, Myan-
mar, Thailand, and Malaysia, and provide an initial attempt
to incorporate a metallogenic framework into the convo-
luted history of the region. Previous reviews by Groves and
Bierlein (2007), Hou and Cook (2009) and Richards (2015)
are extended here by focusing on tectonic processes rather
than only tectonic settings. The review begins by defining
the age and nature of the India-Asia collision. We then dis-
cuss the distinct mineralization seen in ophiolites (thrust
slices of oceanic crust and upper mantle emplaced onto con-
tinental margins) and processes associated with progressive
subduction and island-arc formation, followed by Andean-
type settings where oceanic subduction zones dip beneath
an active granitic-volcanic arc. Finally, we review processes
occurring along continent-continent collision zones typi-
fied by the Himalaya-Tibet region extending into southeast
Asia. A particularly intriguing aspect of this review is that in
some portions of the orogenic belt, such as Afghanistan and
Myanmar, there is a rich metallogenic endowment, whereas
60˚
70˚
80˚
90˚90Eastridge
Maldive-Laccadiveridge
100˚
10˚
20˚
30˚
INDIA
THAILAND
MYANMAR
MALAYSIA
SHAN
AFGHANISTAN
PAMIR
TARIM
QIANGTANG
KUN LUN
Arabian
G
ulf
OMAN
MAKRAN
ZAGROS
KARAKORAM
LADAKH
GANGDESE
Chaman
Fault
Sagaing
Fault
LHASA AndamanIslands
Bentong-Raub
suture
Indus suture
suture
Bangong
Bay of
Bengal
Fig. 1. Digital elevation model of the Middle East and Asia, showing the major tectonic features.

TECTONIC PROCESSES & METALLOGENY, TETHYAN MOUNTAIN RANGES, MIDDLE EAST AND SOUTH ASIA 303
in others, such as along the main Himalayan range, there is
a distinct lack of mineralization.
India-Asia Collision and the Closing of Neotethys
The age of collision of India with Asia has been disputed,
with ages ranging from 65 Ma (Ding et al., 2005; Cai et al.,
2011) to as young as 34 Ma (Aitchison et al., 2007). Paleo-
magnetic data indicate initial contact between India and Asia
during the early Eocene with overlapping paleolatitudes for
the Indian plate Tethyan Himalaya and the Asian plate Lhasa
block occurring at 48.6 ± 6.2 Ma (Najman et al. 2010; van
Hinsbergen et al., 2011a, b). The timing of the India-Asia col-
lision is geologically well constrained at early Eocene based
on a number of lines of evidence. The stratigraphic record
and the geologic record clearly show a marine to continen-
tal transition both along the Indus suture zone and along the
northern Indian shelf margin at ~50.5 Ma (Garzanti et al.,
1987; Beck et al., 1995, 1996; Rowley, 1996, 1998; Searle et
al., 1997b; Zhu et al., 2005; Green et al., 2008; Najman et al.,
2010). This body of work provides unequivocal evidence for
the nature of the collision, with the timing at 50.5 Ma based
on planktonic biostratigraphy. Similar ages obtained for mark-
ers of ocean-continent transition recorded all along the Indus
suture from Pakistan to Tibet suggest that the collision was
essentially coeval.
Structural and geochronological work along the Greater
Himalaya has shown that the Lesser, Greater, and Tethyan
Himalaya were all part of one contiguous Indian plate (Searle
et al., 2003, 2006). The three zones are now bounded by major
Cenozoic thrust faults (e.g. ~25–11 Ma Main Central thrust;
10–0 Ma Main Boundary thrust) and low-angle normal fault
(~25–11 Ma South Tibetan detachment), and restoration has
shown that there was no Mesozoic-Cenozoic ocean between
these zones (Fig. 2, Model A). The closure of the Neotethys
ocean resulted in the formation of the Himalaya and Indo-
Myanmar ranges (Indian plate), as well as enhanced crustal
thickening of the Asian plate margin from the Karakoram
and Hindu Kush ranges in northwestern Pakistan, along the
Lhasa and Qiangtang terranes of south Tibet, and around the
East Himalayan (Namche Barwa) syntaxis into Myanmar and
Thailand (Searle et al., 2011, 2016; Searle and Morley, 2011).
Prior to the closing of Neotethys and the India-Asia collision,
ophiolite thrust sheets were obducted onto the previously
passive continental margin of India and the Burmese plate.
Following the India-Asia collision and closing of Neotethys,
crustal shortening and thickening processes resulted in uplift
of the Himalaya, while Tibet was underthrust by the Indian
lower crust and lithospheric mantle, resulting in enhanced
uplift and thickening.
An alternative model of the India-Asia collision was pre-
sented by van Hinsbergen et al. (2011a, b, 2012) showing
an early “soft collision” of a Tethyan Himalaya microplate
with Asia at ~50 Ma and a later “hard collision” of a contigu-
ous Greater India (Lesser Himalaya and India) between 25
to 20 Ma (Fig. 2, Model B). Their reconstruction shows a
Tibetan (Tethys) Himalaya microplate with an ocean (their
“Greater Indian basin”) approximately 1,000 km wide along
the Greater Himalaya during the period 50 to 25 Ma (van
Hinsbergen et al., 2012, fig. 3). Many decades of study along
the Greater Himalaya sequence have shown that these rocks
are all Neoproterozoic to late Mesozoic protoliths, metamor-
phosed to kyanite and sillimanite grade during the Oligocene-
Miocene, and the southern boundary is a continental ductile
shear zone and thrust fault, the Main central thrust. There
are no oceanic rocks or ophiolites anywhere along the Greater
Himalaya sequence or the Main Central thrust zone, and so
this model lacks any geologic credence.
Thus, we contend that the Tethyan Himalaya, Greater
Himalaya, and Lesser Himalaya were all conjoined as one
Indian plate prior to the collision with Asia and the closing of
Neotethys at 50.5 Ma. After this collision the leading edge of
India was subducted to ultrahigh-pressure depths, resulting
in eclogites preserved along the leading margin in north Paki-
stan and Ladakh. Postcollision crustal thickening resulted in
folding, thrusting, shortening, and regional kyanite-silliman-
ite-grade metamorphism and partial melting during the latest
Eocene-Oligocene-early Miocene (e.g., Hodges, 2000; Searle,
2015).
Comparative Orogenesis
Mountain belts can be broadly divided according to a succes-
sion of stages and processes as follows:
1. Those formed during ophiolite obduction where a thrust
sheet of oceanic lithosphere has been emplaced onto a
previously passive continental margin (e.g., Oman). Typi-
cal mineral deposits include magmatic concentrations of
Cr, Pt, and Ni in ultramafic mantle rocks; exhalative hydro-
thermal Cu-Zn-(Au) deposits in volcanic rocks; and concre-
tionary Mn-Fe nodules associated with pelagic sediment.
2. Island-arc processes above oceanic subduction zones (e.g.,
Andaman Islands; Dras-Kohistan island arc). Typical min-
eral deposits include: porphyry deposits and exhalative
hydrothermal Cu-Zn-Pb deposits hosted in volcanic rocks.
3. Continental magmatic arc formed where an oceanic plate
subducts beneath an active continental margin (e.g.,
Ladakh-Gangdese ranges, south Tibet; Wuntho-Popa arc,
Myanmar). Typical mineral deposits include magmatic-
hydrothermal porphyry Cu-Mo-(Au) and epithermal
Au-Ag deposits associated with I-type granite magmas; and
magmatic-hydrothermal Sn-W deposits associated with
S-type granite magmas from the continental side of the arc.
4. Early-stage continental collision (e.g., Zagros Mountains,
Iran). These mountain belts reflect thickened crust and
high-grade metamorphic rocks, and have large porphyry
deposits (Shafiei et al., 2009; Richards and Sholeh, 2016).
5. Late-stage continental collision where two continental
plates have collided (e.g., Himalaya; Mogok belt, Myan-
mar; West Malaysia). These mountain belts reflect thick-
ened crust, regional high-grade metamorphic rocks, and
anatectic leucogranitic and pegmatitic melts, and also
generally lack large-scale mineral deposits. They do, how-
ever, contain small deposits associated with enrichments
of U-Th-REE-Sn in leucogranites as well as gem miner-
als (ruby, sapphire, emerald) hosted in metamorphic rocks
and pegmatites.
6. Long-lived plateau-type mountains with both pre- and
postcollision history (e.g., Tibet) with a long history of
crustal thickening, metamorphism, melting, and miner-
alization. These mountain belts can include a variety of

304 SEARLE ET AL.
mineral deposits linked to previous stages of the orogenic
cycle (Deng et al., 2014; Richards, 2015). Some porphyry
Cu-Mo deposits in Tibet are postcollisional (Miocene)
within more evolved adakite-like intrusive rocks.
7. Long-lived mountains formed by double-vergent conti-
nental subduction systems (e.g., Karakoram, Pamir; Searle
et al., 2010a; Stearns et al., 2013). As with continental col-
lision belts these terranes show long-lived crustal thicken-
ing, metamorphism, and melting histories, but typically
lack major mineral deposit types.
8. Old mountain ranges reactivated and uplifted by younger
tectonics (e.g., Afghanistan, Hindu Kush, Tien Shan, Kun
Lun ranges). Major mineral deposits formed at upper
crustal levels would have been eroded away, but deeper
sourced deposits, such as orogenic gold, may be preserved
and reflect processes active in past orogenic cycles.
Each type of mountain range has a distinctive geologic
fingerprint, distinct igneous and metamorphic assemblages,
and distinct structural style. Specific mineral deposits can be
linked to each type of mountain belt and its tectonic setting,
in both space and time. The combination of geologic and
geochemical fingerprinting can be linked to specific mineral
deposits in order to gain understanding of processes required
INDIA
OMAN
LhasaNeo- TethysHIMALAYA
INDIA
GREATER
HIMALAYA
TETHYAN
LESSER
Neo - Tethys
Burm
a
Ladakh
Lhasa
Gangdese
Kohistan
60 Ma
MODEL A MODEL B
A’
A
60 Ma
50 Ma
30°N
60°E 90°E
30°N
60°E 90°E
0°
0°
A
B
B
C
C’
B B’LhasaNeotethys
ophiolite
equatorial slab
SE Asia
Paleogene Himalayan
subduction zone
India
GIB
B’
Lhasa
Greater Indian Basin(s)
ophiolites Tibetan Himalaya
LesserH
im
alaya
extended 2.500 ± 820 km
C C’
India
GIB
Microcontinent
collision
forearc
‘microcontinent collision’
MODEL A
One contiguous Indian plate
India - Asia collision ~50 Ma
MODEL B
Tibetan Himalaya plate
Greater Indian basin
Indian plate
‘Soft’ collision ~ 50 Ma
‘Hard’ collision ~ 25-20 Ma
Fig. 2. Models for the India-Asia collision. Model A shows a single contiguous Indian plate (conjoined Lesser-Greater-
Tethyan Himalaya), with closure of Neotethys at 50 Ma. Model B, after van Hinsbergen et al. (2012), shows a separated
Tibetan Himalaya microplate with an intervening ocean the Greater Indian basin (GIB) separating this from the main Indian
plate This model involves a “soft collision” at 50 Ma and a “hard collision” at 25 to 20 Ma.

to generate and preserve each mineral province. Examples
of each type of mountain belt listed above occur along the
Tethyan mountain ranges of the Middle East and Asia.
Himalaya-Karakoram-Tibet Orogenic Cycle
The India-Asia collision zone lies along the Indus-Tsangpo
suture zone that divides the Indian plate Himalaya to the
south from the Asian plate Lhasa and Qiangtang terranes
of the Tibetan plateau to the north (Fig. 3). The Himalayan
mountain range stretches in an arc from northwestern Paki-
stan eastward across Ladakh (NW India), southern Tibet to
Yunnan, and the East Himalayan syntaxis region. The Hima-
layan orogenic cycle can be temporally divided into five stages
(Fig. 4): (1) Late Cretaceous-Paleocene precollision ophiolite
obduction stage (~ 65 Ma; Fig. 4a); (2) crustal subduction and
formation of ultrahigh-pressure eclogite facies metamorphism
(~57–47 Ma; Fig. 4b); (3) crustal thickening along the Hima-
laya and peak kyanite-grade metamorphism (~35–30 Ma;
Fig. 4c); (4) decompression melting, formation of migma-
tites and leucogranites, and south-directed extrusion of the
ductile midcrust by channel flow (~24–15 Ma; Fig. 4d); and
(5) southward-propagating thrusting along the Lesser Hima-
laya forming a subcritical wedge with active underthusting of
India beneath the Himalaya and south Tibet.
This tectonic evolution is well constrained by structural
mapping combined with extensive thermobarometric and
U-Pb zircon and monazite dating (e.g., Searle and Rex, 1989;
Grujic et al., 2002; Searle et al., 1999, 2010a, b; Streule et al.,
2010). Timing of mineralization can be linked both spatially
and temporally to this basic framework.
For the Asian side of the India-Asia collision zone in the
Karakoram and Pamir ranges as well as across the Lhasa and
Qiangtang blocks of Tibet, stratigraphic and structural data
combined with geochronology suggest the following broad tec-
tonic evolution phases: (1) Triassic-Early Jurassic crustal thick-
ening and regional metamorphism, the Indosinian orogeny
(e.g., Weller et al., 2013); (2) pre-India-Asia collision crustal
thickening in an Andean-type setting over a period spanning
Early Jurassic-early Eocene, along the Kohistan-Ladakh-
Gangdese batholiths (~198–49 Ma; Chung et al., 2005; Chu
et al., 2006); (3) postcollisional crustal thickening resulting in
areas of kyanite- and sillimanite-grade metamorphism formed
500 km0
MMT
STD
MCT
MBT
Indian Plate
Transhimalayan batholith
Kohistan arc
Ophiolites
Indus Tsangpo suture zone
Tethyan zone
Greater Himalayan sequence
Lesser Himalaya
TBM
TCM
TCM
TBM
T
C
M
TBMTFM
P
K
ZSZ
DTS
DTS
DTS
S
ZSS
KudniH
hsu
Karakoram
Kohistan
hkadaL
Kathmandu Darjeeling
TKM
Pamir
Indus Suture zone
Lhasa Block
Indian Plate
Hazara
P - Peshawar basin
K - Kashmir basin
S - Sutlej basin
SSZ - Shyok suture zone
MKT - Main Karakoram Thrust
ZSZ - Zanskar Shear zone
MFT - Main Frontal Thrust
Main Zanskar backhrust
South Tibetan Detachment
Main Central Thrust
Main Boundary Thrust
Main Mantle Thrust
Nanga Parbat
Bhutan
Everest
Zanskar
90°E
26°N
30°N
84°E
78°E
75°E
Karakoram
fault
Spontang
ophiolite
Tso Morari
Kaghan
Tibetan Plateau
Indian Plate
70°E 80°E 90°E 100°E 110°E
40°N
30°N
20°N
10°N
Fig. 3. Simplified geologic map of the Himalayan region.

306 SEARLE ET AL.
30
km
0
Indus molasse
basin
thinned continental
crust
Indus
suture
zone
Ladakh
batholith
Ladakh
batholith
Ladakh
batholith
Tethyan oceanic
crust form
eclogite root
Greater Himalayan
nappes
Pz Mz
kyanite grade
metamorphism
Folded isograds of
Greater Himalaya
Zanskar
shear zone
Spontang
ophiolite
klippe
Indus
molasse
Ladakh
batholith
Zanskar
pop-up
structure
North
Zanskar
Backthrusts
inverted metamorphic
isograds along MCT
Lesser Himalaya
protolith
Final marine
sediments in
Indus suture zone
exhuming
Tso Morari eclogite
Tso Morari eclogite
Tso Morari
protolith
ARCHAEAN INDIAN SHIELD
PROTEROZOIC - PALAEOZOIC
30
km
0
PROTEROZOIC - PZ
30
km
0
30
km
0
INDIAN PLATE
PERMIAN - MESOZOIC
(b) Crustal subduction, UHP metamorphism (ca. 50 Ma)
(a) Ophiolite obduction stage (ca. 65 Ma)
(c) Himalayan crustal thickening,
peak kyanite-grade metamorphism (ca. 35 Ma)
(d) Himalayan metamorphism (peak sillimanite grade) and
crustal melting (leucogranites) ca. 20 Ma. Ductile extrusion of mid-crustal channel
Spontang Ophiolite thrust sheet
Zanskar thrust sheets
NESW
NH
TM
TM
TM
TMMAIN CENTRAL THRUST ZONE
SILLIMANITE GRADE METAMORPHISM
Leucogranites, migmatites

during the Cenozoic (Palin et al., 2013); (4) postcollisional,
within-plate alkaline (potassic, sodic) magmatism formed by
lower crustal melting to produce adakite-like intrusions, and
mantle-derived melting to produce shoshonites (Chung et al.,
2005, 2009; Lee et al., 2009, Wang et al., 2010); and (5) Oligo-
cene-Miocene crustal thickening and regional metamorphism
along the Karakoram (Searle et al., 2010a) and Pamir (Stearns
et al., 2013).
In Myanmar various Tibetan terranes have been affected by
clockwise rotation around the East Himalayan syntaxis, later
transpression along continental-scale strike-slip faults (e.g.,
the Sagaing fault), arc formation (Wuntho-Popa arc), and
deep subduction seen along the Burma seismic zone (Searle
and Morley, 2011).
Ophiolites
Ophiolite complexes are recorded in four major tectonic set-
tings along the Tethyan mountain ranges of the Middle East
and Asia: (1) large thrust sheets obducted onto previously
passive continental margins (e.g., Oman ophiolite; Fig. 5),
(2) ophiolites trapped along suture zones (e.g., Indus suture
zone ophiolites), (3) high-pressure ophiolites exhumed from
subduction zones (e.g., Jade belt, Myanmar), and (4) ophi-
olitic rocks exposed in accretionary prism complexes above
active subduction zones (e.g., Andaman island ophiolite). The
mantle portion of ophiolite complexes (harzburgites, lherzo-
lites, dunites) is dominated by magmatic concentrations of
chromium, vanadium, platinum, copper, and nickel, whereas
crustal sequences of ophiolites preserve concentrations of
chalcophile metals (copper-zinc) associated with ocean-water
circulation and venting. The uppermost ocean floor levels of
ophiolites commonly have Fe- and Mn-rich umbers and nod-
ules, similar to those dredged from deep ocean basins.
Large ophiolite thrust sheets
The Oman (Semail) ophiolite in eastern Arabia is the largest
and best exposed example of a relatively intact thrust sheet of
oceanic crust and upper mantle emplaced onto a previously
passive continental margin anywhere in the world. In recon-
structed sections the ophiolite includes a 6- to 7-km-thick
sequence of crustal rocks and over 15 km of upper mantle
peridotites, including depleted harzburgites, lherzolites, and
dunites (Fig. 5). Mantle peridotites host podiform chromites
and concentrations of vanadium and platinum group metals.
These metals clearly originate from the mantle and may be
concentrated to ore grades by processes such as fractional
crystallization, sulfide-silicate liquid immiscibility. The recent
discovery of microdiamonds as well as a range of highly
reduced minerals (Ni-Mn-Co alloys, Fe-Si and Fe-C phases,
stishovite, moissanite) as inclusions in chromitites and peri-
dotites, notably in the Luobusa ophiolite, south Tibet, are
consistent with the suggestion that some mineral inclusions in
ophiolite mantle sequences may have a deeper origin, possi-
bly near the upper-lower mantle transition zone between the
410- to 660-km discontinuities (Yang et al., 2014). Diamonds
formed in situ in ophiolites, for example, reflect depths of
150 to 300 km, far deeper than the origin of suprasubduction
zone ophiolites (Yang et al., 2007). These authors proposed a
model involving a deep mantle plume rising beneath a spread-
ing ridge bringing deep mantle minerals upward, followed by
normal ophiolite obduction processes to emplace these oce-
anic thrust sheets onto continental margins.
The upper sections of the ophiolite crustal section are
composed of a series of pillow lavas, including depleted arc
tholeiites and boninites (high Mg andesites) overlying ocean
ridge basalts, with interbedded radiolarian cherts at higher
structural levels. Geochemical compositions of the lavas in
the Oman ophiolite suggest that all units formed in a suprasu-
bduction zone environment (Pearce et al., 1981; MacLeod et
al., 2013). Immobile elements (Ti, Y, Nb, V, etc.) can poten-
tially distinguish between MORB and suprasubduction zone
settings and have been used as proxies to interpret fraction-
ation processes, alkalinity, and temperature as well as tec-
tonic setting (Pearce et al., 1981). In many ophiolites such as
Oman, Troodos (Cyprus), and the Bay of Islands (Newfound-
land), there appears to be no obvious island arc preserved in
the ophiolite even though the lavas are clearly tholeiitic and
boninitic in composition. For this reason, these ophiolites are
commonly referred to as suprasubduction zone ophiolites.
The basalts are fed by a series of sheeted dikes pointing to
100% crustal extension at a ridge axis. In Oman individual
doleritic dikes can be mapped out as feeder dikes to the lower
Geotimes series and the later Lasail arc-related boninites and
arc tholeiites. Volcanogenic massive sulfide (VMS) deposits
are known to occur throughout the lava series and have been
mined at Lasail in northern Oman, as well as extensively in
Cyprus.
The sheeted dikes feed magma up from a magma cham-
ber that is represented by homogeneous gabbros that become
progressively more layered toward their base. The ophiol-
ite lower crust rocks represent a dynamic magma chamber
beneath a spreading ridge, continually replenished by man-
tle-derived melts from below and continually feeding magma
up to the sheeted dike and basaltic pillow lavas above. More
primitive magmas are represented by gabbro norites, whereas
late-stage wehrlites (olivine + clinopyroxene) that cut the lay-
ered gabbros are thought to be plutonic equivalents of later
arc magmatism.
Processes involved in the thrusting of ophiolites onto passive
continental margins can be deduced from studies of the meta-
morphic sole rocks. These are typically granulite, amphibolite,
and greenschist facies rocks, showing a narrow, inverted, and
highly condensed P-T gradient and intense mylonite fabrics
(e.g., Searle and Cox, 2002; Cowan et al., 2014). U-Pb dating
Fig. 4. Model for the evolution of the western Himalaya showing four stages of (a) precollision ophiolite obduction stage,
(b) deep crustal subduction of the leading margin of India to coesite eclogite ultrahigh-pressure depths, (c) the major crustal
thickening event resulting in kyanite grade metamorphism, and (d) peak sillimanite grade metamorphism with widespread
partial melting and generation of migmatites and leucogranites. This stage resulted in ductile extrusion of the partially molten
middle crust (channel flow, shown in pink; after Searle et al., 1997a). Abbreviations: Mz = Mesozoic, NH = North Himalaya,
Pz = Paleozoic, TM = Tso Morari eclogites.

308 SEARLE ET AL.
20
15
10
MOHO
TRANSITION
ZONE
5
0
km
MANTLESEQUENCECRUSTALSEQUENCE
Semail Thrust
METAMORPHIC
SOLE
LAYERED
GABBRO
GABBRO
SHEETED
DIKES
PILLOW
LAVAS
gabbro
dunite
harzburgite
amphibolite
greenschist
wehrlite
VMS deposits
MAGMATIC
PGE-Ni-Cu
PODIFORM
CHROMITE
Fig. 5. Tectono-stratigraphic column for the Semail ophiolite complex in Oman, after Searle (2007).

of zircons in the sole amphibolites and the more fractionated
gabbro-tonalite-trondhjemite ophiolite rocks shows that sub-
duction zone sole rocks formed at precisely the same time as
the ophiolite crustal sequence formation (Rioux et al., 2013).
Possible processes involved include: (1) slab pull, required
to get more buoyant continental crust deep into the mantle;
(2) slab break-off, required to release the buoyant slice of
ultrahigh-pressure eclogitic material; or (3) rapid exhumation
of the ultrahigh-pressure slice back up the same subduction
zone, driven by buoyancy contrasts.
Ophiolites along suture zones
Several examples are known of ophiolites trapped along the
Indus-Yarlung Tsangpo suture zone that demarcates the
India-Asia collision (Fig. 4). These include the ophiolitic
mélanges and Nidar ophiolite complex in the Ladakh segment
and the Kiogar-Amlang-la ophiolites of southwestern Tibet.
Many Tethyan ophiolites in southern Tibet (e.g., the Luo-
busa, Zedang, Xigase, Purang, and Dongbo massifs) are either
trapped within the Yarlung-Tsangpo suture zone or occur
along the northern margin of the Indian plate. These ophiol-
ites are commonly structurally broken up and fault-bounded,
and in some cases occur within a giant mélange (e.g., Kiogar,
Amlang-la ophiolites). It is not possible to accurately deter-
mine processes involved in their emplacement due to later
subsequent structural overprinting. Several of these ophiolite
complexes, notably the Luobusa ophiolite, show the range of
deep mantle ultrahigh-pressure mineral inclusions in chro-
mitites, including coesite the high-pressure polymorph of
quartz, and microdiamond (Yang et al., 2014).
Ophiolite complexes also mark the line of older suture
zones across the Tibetan plateau, particularly along the Shyok
and Bangong-Nujiang sutures and their extensions farther
southeast into Myanmar (Fig. 6). In Ladakh the Nidar ophi-
olite is a suture zone ophiolite preserved along the Indus-
Tsangpo suture zone in Ladakh. In Myanmar the Myitkyina
ophiolite also represents a suture zone ophiolite, although the
exact trace of the main India-Asia suture, thought be along
the Mount Victoria belt in the eastern Indo-Myanmar ranges,
remains unknown.
High-pressure ophiolites
The Jade mines ophiolites in the Hpakant region of Kachin
State, northwestern Myanmar, are examples of ophiolitic
rocks that have been exhumed from subduction zones and
preserved their high-pressure mineral assemblages (Fig. 6).
The Jade mines belt is composed dominantly of ophiolitic
mantle-derived rocks that have been subjected to high-pres-
sure metamorphism and direct crystallization from Na-rich
fluids during the serpentinization process. A possible source
for the fluid may be seawater that is drawn down the sub-
duction zone and ultimately linked to the process of serpen-
tinization of peridotite, and also perhaps with the formation
of rodingites (Ca-metasomatized gabbro or plagiogranite), or
pyroxenite (Wang et al., 2012), both during subseafloor hydro-
thermal metamorphism and subsequently in the subduction
channel.
Two main types of “jade” occur, a monomineralic pyroxene
jadeite (NaAlSi2O6) and a lower pressure amphibole jade or
nephrite, comprising tremolite-actinolite (Ca2(Mg,Fe)5Si8O22
(OH)2). The emerald green color in some Burmese jade
(Imperial Jade) results from chromium (Cr3+) enrichment,
particularly associated with the Cr-rich pyroxene kosmochlor
(NaCrSi2O6) in the variety known as Maw-sit-sit (Gübe-
lin, 1965a, b). Pale mauve varieties result from manganese
(Mn2+) enrichment, and blue-green varieties from iron (Fe2+
and Fe3+) enrichment. Although jadeitites are high-pressure
rocks their P-T conditions lie in the blueschist-eclogite facies
transition (Sorensen and Harlow, 1999; Harlow and Sorensen,
2001). They require devolatilization of fluids derived from
serpentinized ultramafic rocks, perhaps from above the sub-
ducting oceanic slab.
The Jade mines belt is dominated by serpentinite and peri-
dotite, but owing to thick laterite and jungle cover is very
poorly exposed. The majority of mined jade and analyzed
material comes from rounded boulders apparently exposed in
young alluvial deposits, particularly along the Uru River. The
Uru Conglomerate, described by Chhibber (1934), is the host
to most of the jadeite extraction although at least one primary
jadeite occurrence is found at the PNO mine (Nant Maw),
which is a lozenge-shaped body encapsulated in a shear zone
(Douglas Kirwin, pers. commun., 2016). However, given the
size of the jade boulders and classic serpentinite weather-
ing pattern of ultramafic rocks it is suggested that some of
the “boulders” are actually remnant serpentinite weathering
of large in situ ophiolitic peridotite sheets, and are not allu-
vial. In addition to the abundant ultramafic clasts, Goffé et al.
(2002) reported a variety of jade rock assemblages, including
pure jadeitite, amphibole-jadeite, omphacite-jadeite-zoisite-
kyanite, and kosmochlor with chromite, as well as less com-
mon eclogite, amphibolite, and blueschist.
There is consensus that the jade rocks formed at high pres-
sure and low temperature, although P-T conditions are not
precisely constrained, owing to the predominance of high-vari-
ance mineral assemblages, with estimates of peak conditions
falling in the broad range of 10 to 15 kbars, 300° to 500°C (Shi
et al., 2012). A more complex metamorphic history is implied
by the suite of rocks studied by Goffé et al. (2002), where
the sequence of overprinting assemblages seen in eclogite,
jade veins, amphibolite, and blueschist implies a four-stage
evolution from (1) an eclogitic stage at P ≥14 kbars, 550° to
600°C; (2) overprinting by amphibole-epidote-albite during
decompression to ~8 kbars, 500° to 550°C; (3) blueschist-
facies conditions at P ≥14 kbars, 400° to 450°C, with jadeitite
vein formation at this stage; and (4) cooling and decompres-
sion represented by pumpellyite and albite-nepheline partial
replacements.
It is suggested that the protolith of the Burmese Hpakan
jadeitites may have been older components of a late Meso-
zoic ophiolitic suite obducted onto the Myanmar plate, and
that the high-pressure metamorphism was Late Cretaceous in
age (Searle et al., 2016). The slice of high-pressure peridotite-
jadeitite could have been exhumed by obduction from the
subduction channel and then offset by late Cenozoic dextral
transpressional shearing along the Sagaing fault (Searle et al.,
2016).
Accretionary prism ophiolites
Accretionary prism ophiolites are tectonically dismem-
bered slices of oceanic crust that occur in the hanging wall

310 SEARLE ET AL.
RanongFault
SagaingFault
Three
Pagodas
Fault
MaeYuamFault
KhlongMaruiFault
M
ae
Ping
Fault NOTNEBG-ERUTUSBUAR
CHIANGRAILINE
LANCANGJIANG
ZONE
GRANITE PROVINCES
Eastern (I-type)
Main Range (S-type)
Northern Thailand
Migmatitic Complex
Mogok-Mandalay-Mergui Belt
Wuntho-Popa Arc
(S-type)
400 km
SUNDA
TRENCH
12°
4°
110°106°102°98°
PENINSULAR
MALAYSIA
CAMBODIA
THAILAND
LAOS
VIETNAM
CHINA
MYANMAR
Bangkok
Mogok
Yangon SukhothaiArc
SUMATRA
TIN ISLANDS
BORNEO
Kuala
Lumpur
Phuket
Singapore
Tioman
Island
Myeik
NANSUTURE
Monywa
Shangalon
Mawchi
Dawei
Wunth
o
Kyaukpahto
Mengapur
Modi-Taung
Shante
ShanScarp
BurmaSeismicZone
Hpakant (Jade Mines)
Mandalay
Thabeikkyin
Sungai Lembing
Raub
Penjom
Selinsing
SlateBelt
Fig. 6. Geologic map of Myanmar and southeast Asia, after Cobbing et al. (1986) and Searle et al. (2007), showing major
suture zone, faults, and granite provinces.

of a subduction zone. In some cases (e.g., Franciscan high-
pressure mélanges, California) they are associated with high-
pressure blueschists and eclogites recording some of the
subducted crustal rocks. In other cases (e.g., Andaman Islands
ophiolite) they are not associated with high- or ultrahigh-pres-
sure rocks and form structural slices in the upper plate. The
Andaman ophiolites are presently exposed within an accre-
tionary prism that lies above the active Andaman-Nicobar-
Sumatra subduction zone. The Andaman ophiolites form the
basement of the Andaman Islands, part of the outer forearc
to the Sumatra volcanic arc. Upper mantle harzburgite and
dunite are overlain by a cumulate peridotite-gabbro complex,
high-level intrusive rocks, and both tholeiitic and calc-alkaline
volcanic rocks. The upper crust of the South Andaman ophio-
lite shows a prominent trondhjemite-diorite-andesite volcanic
suite, suggesting that arc volcanism was built on oceanic crust.
Zircon U-Pb dating of a trondhjemitic rock from Chiriya Tapu
in South Andaman Island at 94.6 ± 1.3 Ma (Pedersen et al.,
2001) is remarkably similar to U-Pb ages of the Troodos ophi-
olite, Cyprus, and the Semail ophiolite, Oman.
Island Arcs and Subduction Zones
Kohistan island arc
In the western Himalaya a large-scale Late Cretaceous to
Paleocene-Eocene island-arc complex, the Kohistan-Dras
island arc, crops out within the Tethyan suture zone between
India and Asia, bounded by two sutures, the Shyok suture to
the north and the Indus suture (Main mantle thrust) to the
south (Jan and Howie, 1981; Khan et al., 1993; Pettersen and
Treloar, 2004; Dhuime et al., 2007; Garrido et al., 2007; Jag-
outz et al., 2007; Jagoutz and Schmidt, 2012). The Kohistan
arc comprises a complete crustal section through an island arc
together with a slice of upper mantle peridotite (Fig. 7). The
mantle component includes the ultramafic lower part of the
Jijal complex (layered dunite, wehrlite, Cr-rich pyroxenites
overlain by websterites and pyroxenites; Dhuime et al., 2007;
Garrido et al., 2007), and the Sapat ultramafic (dunite, harz-
burgite) thrust slices. The latter includes unique gem-qual-
ity peridot (olivine) in the dunites. The crustal component
includes the upper part of the Jijal complex, garnet granulites,
and basal amphibolites of MORB affinity (Kiru and Kamila
complexes; Jagoutz and Schmidt, 2012). The Chilas com-
plex is dominantly composed of gabbronorites and diorites
with some ultramafic components at lower structural levels
(dunite, lherzolite, pyroxenite). It is possible that the base of
the Chilas complex is a thrust contact bringing deeper mantle
and lower crust over shallower parts of the midcrust amphibo-
lites (Kamila amphibolites). Overlying the Chilas complex is
a series of andesitic-dacitic volcanic complexes (Dir, Utror,
Shamran, and Chalt volcanic suites). All these rocks have been
intruded by extensive biotite- and hornblende-bearing mon-
zogranites, granodiorites, and tonalites of the Kohistan batho-
lith. The eastward extension of this batholith in Ladakh and
Gangdese, south Tibet, has U-Pb zircon ages ranging from ca.
198 to 49 Ma (Chung et al., 2003, 2005; Wen et al., 2008a, b).
The Kohistan arc was an intraoceanic island arc formed
above a N-dipping subduction zone and obducted onto the
northern margin of India (Khan et al., 1993; Searle et al., 1999;
Jagoutz and Schmidt, 2012). A second long-lived subduction
zone dipping northward beneath the Asian margin lasted
from at least the late Jurassic through the Cretaceous to the
early Eocene (Chiu et al., 2009). Subduction-related I-type
granite magmatism characterizes the magmatic evolution of
both northern Kohistan and the Karakoram terrane to the
north (Searle et al., 1999). Much of the succession of crustal
sedimentary rocks of the north Indian plate margin (Tethyan
Himalaya), comprising up to 5 km of stratigraphic thickness in
Ladakh, has been removed by tectonics and erosion in Paki-
stan, such that the Kohistan arc lies above high-grade regional
metamorphic rocks of the Greater Himalayan sequence.
Mineralization in island arcs is dominated by VMS-type
deposits (Cu-Zn-Pb ± Au-Ag) related to exhalative hydrother-
mal fluid circulation on the ocean floor and hosted in inter-
mediate-felsic volcanic rocks. The Dras-Kohistan arc contains
some indications of massive sulfide mineralization but none of
these has proven economically viable—erosion may also have
destroyed the bigger deposits. The Himalayan arc systems
in particular have been subjected to subsequent collision-
related regional Barrovian metamorphism and extreme struc-
tural shortening, which accentuated the uplift and erosion of
higher levels of the arc system.
Andean-Type Continental Margins in
Tibet and Myanmar
Ladakh-Gangdese granite batholith
Along the southern margin of the Lhasa terrane (south Asian
margin) a 2,500-km-long batholith composed mainly of I-type
hornblende- and biotite-bearing granites, granodiorites, and
diorites crops out from northern Kohistan (Pakistan) across
Ladakh and southern Tibet along the southern margin of
the Asian plate (Fig. 3). These Ladakh-Gangdese granites
are related to the northward subduction of Tethyan oceanic
lithosphere beneath the south Asian continental margin. The
granites have an extensive calc-alkaline volcanic superstruc-
ture comprising andesites, rhyolites, and ignimbrite flows
(Linzizong volcanic rocks; Ding et al., 2005; Kapp et al., 2007;
Mo et al., 2007, 2008; Wen et al., 2008a, b; Chiu et al., 2009)
of similar composition and areal extent to the central Andean
volcanic province (Pitcher, 1987). Zircon U-Pb ages of Gang-
dese granites range from Early Jurassic to early Eocene (198–
49 Ma), suggesting long-lasting I-type magmatism (Chung et
al., 2005; Chu et al., 2006). Zircon U-Pb ages from the Gang-
dese granites and 40Ar-39Ar ages from the Linzizong volcanic
sequence show two distinct peaks of magmatism, a widespread
Cretaceous stage (~133–110 Ma), and an intense magmatic
“flare-up” in the Paleocene (66–57 Ma) when compositions
varied from low K tholeiite through calc-alkaline andesite to
shoshonitic suites (Chiu et al., 2009; Lee et al., 2009).
Both Ladakh-Gangdese granitoids and Linzizong-type
andesite-ignimbrite volcanic rocks ceased around the time of
Indian plate collision as oceanic subduction beneath the south
Asian margin ended. Final magmatism along the Kohistan-
Ladakh part of the batholith comprised a series of peralumi-
nous garnet-bearing leucogranitic dikes (Indus confluence
dikes in Kohistan; Chumatang dikes in Ladakh) formed by
extreme differentiation of the initial calc-alkaline batho-
lith or melting of a predominantly sedimentary protolith in
the source. After 47 Ma no subduction-related calc-alkaline

312 SEARLE ET AL.
?
60
70
50
40
30
20
10
5
km
0
KOHISTAN ISLAND ARC (Cenomanian - Paleocene)
Hunza Volcanic rocks
meta-sediments
gabbro norite
(ol + opx + cpx + pl)
dunite, Iherzolite, pyroxenite
amphibolite (pl + hbl ± grt ± qtz)
ms - leucogranite
Kiru - Kamila amphibolite
meta-basalt
hornblende diorite
Sarangar gabbro
(cpx + pl + hbl + grt)
Garnet granulite meta-gabbro
+ hornblendite
Pyroxenite: websterite, dunite
Peridotite: dunite, wehrlite
SAPAT OPHIOLITE
MÉLANGE
INDIAN
PLATE
UHP eclogite
facies gneisses
meta-gabbro, diorite, tonalite
(pl + qtz + hbl + grt)
harzburgite (ol + opx)
dunite (ol ± chr spinel)
97.1 ± 0.2 Ma
91.8 ± 1.4 Ma
118 ± 12 Ma
94 ± 4.7
83 ± 10
85.7 ± 0.15 Ma
Yasin Group limestone
Shamran Volcanic rocks
basalts, andesites
I-typegranites
42.1 ± 3.7 Ma
57.3 ± 5.3 Ma
62.1 ± 4.9 Ma
67.4 ± 5.8 Ma
72.3 ± 5.1 Ma
75.1 ± 4.5 Ma
Ghizar Volcanic rocks dacites, rhyolites
andesites, rhyolites,
tuffs, ignimbrites
red beds
MOHOMOHO
GILGITCOMPLEX
CHILAS
COMPLEX
KAMILA
COMPLEX
JIJAL
COMPLEX
KOHISTAN
GRANITES
CHALT
VOLCANICSGP
SHAMRAN
VOLCANICS
GP
Fig. 7. Tectono-stratigraphic column for the Kohistan island arc (north Pakistan). Abbreviations: chr = chrome spinel, cpx
= clinopyroxene, grt = garnet, hbl = hornblende, ol = olivine, opx = orthopyroxene, pl = plagioclase, U-Pb age data from
Kohistan granites and diorites are from Schaltegger et al. (2002), Jagoutz et al. (2009), and Bouilhol et al. (2013). Sm-Nd
isochron ages for Jijal complex granuiltes are from Yamamoto and Nakamura (2000).

magmatism is recorded. Plutons substantially younger than ca.
45 to 40 Ma are distinct and have an alkaline chemical compo-
sition and are related to slab break-off and lower crustal melt-
ing to produce postcollisional adakite-like magmas (Chung et
al., 2005).
Seven major porphyry Cu-Mo ± Au deposits with ages
spanning 120 to 12 Ma (Jiama, Qulong, Lakang, Nanmu,
Tinggong, Chongjiang, Dongga) are all hosted either within
the Gangdese granite batholith (Tafti et al., 2001; Yang et al.,
2009; Wang et al., 2014a, b) and their extrusive equivalents
(the ~65–43 Ma Linzizong andesites), or in Miocene ada-
kites (Qu et al., 2009; Wang et al., 2014; Richards, 2015; Fig.
8). Some porphyry deposits including the Yulong (46.5 Ma)
and Malasongduo (42.5 Ma) deposits were formed immedi-
ately after the India-Asia collision (Hou et al., 2003; Rich-
ards, 2015). These deposits are related to fluids driven off the
subducting slab and are generally hosted in evolved I-type
granites that have been affected by metasomatism. Copper
and other metals are transported by hot saline fluids and pre-
cipitated in fractures within the high-level granites (Richards,
2015). Others, such as the giant Qulong porphyry Cu-Mo
deposit (16.4 ± 0.5 Ma; Yang et al., 2005) are younger. Zhu
et al. (2009) described Early Cretaceous adakite-like rocks
(Si-rich, high Sr/Y and La/Yb) with zircon SHRIMP ages of
~136 Ma, which are clearly part of the subduction-related
Gangdese batholith. Some precollisional Gangdese zircons
have younger rim ages spanning 26.0 to 17.7 Ma (Qu et al.,
2009) but it is unclear precisely what these ages reflect.
Gangdese magmatism is thought to be the product of con-
tinuous subduction of Tethyan oceanic lithosphere beneath
Asia from Late Jurassic until the early Eocene Indian plate
collision. The precollision adakites are interpreted as derived
from partial melting of subducted Neo-Tethyan slab (MORB
+ sediment + fluid) subsequently having been hybridized by
peridotite in the mantle wedge (Zhu et al., 2009). Following
collision, oceanic subduction beneath Tibet ceased, calc-alka-
line magmatism ended, and magmatism evolved to more alka-
line adakite-like compositions, as the crust thickened.
Adakite-like intrusions in south Tibet
Adakite-like plutonic and volcanic rocks formed both during
the arc thickening phase prior to continental collision and dur-
ing the postcollisional phase across southern Tibet. Adakites
(sensu stricto) are high silica, low Y, and heavy REE, and high
Sr/Y and La/Yb igneous rocks formed by fractional crystalliza-
tion of mafic magmas that must have had garnet, hornblende,
or clinopyroxene in an eclogite or amphibolite lower crustal
source (Martin, 1988; Defant and Drummond, 1990; Castillo,
2012). Adakites were originally described from melting of
thickening lower crust of island arcs such as the Aleutian arc
(Kay and Kay, 2002), but they have also been described from
areas of thickened crust such as Tibet (Chung et al., 2005).
Gangdese batholith (~120 - 40 Ma) Porphyry Copper deposits
Calc-alkaline granite (60 - 120 Ma)
Adakite-like granite (Eocene)
Porphyry intrusion (10-20 Ma)
Normal fault
Graben
Ore deposit
1. Jiama
2. Qulong
3. Lakang
4. Nanmu
5. Tinggong
6. Chongjiang
7. Dongga
80° 84° 88° 92° 96°
92°E88°E
29°N
30°N
100°
80° 84° 88° 92° 96° 100°
36°
32°
28°
36°
32°
28°
INDIA
HIMALAYA
Lhasa
Lhasa Terrane
Yulong
Porphyry
Belt
Qiangtang Terrane
Indus
Suture
Kunlun - Muztagh Suture
Jinsha Suture
Bangong Nujiang Suture
Main Boundary Thrust
20 km
Xigaze
Nanmuliu
Xigaze forearc basin
Tethyan Himalaya
thrust
Indus - Tsangpo suture zone
Lhasa Terrane
Triassic - Cenozoic volcanic - sedimentary sequence
Ophiolites
Lhasa
QuxuQ Q
Q
Q
Gangdese
N
5 4
3
2
1
6
7
Fig. 8. Geologic map of the Gangdese batholith, south Tibet, after Hou et al. (2009, 2011), showing major porphyry Cu (+Mo
±Au) deposits.

314 SEARLE ET AL.
In southern Tibet a distinct change in magmatism occurred
soon after the time of the India-Asia collision (~50.5 Ma; Zhu
et al., 2005; Green et al., 2008). Small-volume, alkaline gran-
itoids with minor volcanic flows were formed between ~30
to 9 Ma (Chung et al., 2003, 2005; Hou et al., 2003). Crustal
thickening resulted in high K and high Na adakite-like mag-
mas formed from melting a garnet-bearing lower crust source
(Chung et al., 2005). Along the Gangdese belt of south Tibet
an important suite of Oligocene-Miocene porphyry Cu depos-
its are related to syn- to postcollisional adakite-like intrusions,
based on young U-Pb zircon ages (Wang et al., 2014; Rich-
ards, 2015). Hou et al. (2009, 2011), Yang et al. (2009), and
Wang et al. (2014) reported Miocene U-Pb (SHRIMP) ages
and Re-Os molybdenite ages (22.2–15.3 Ma) for some of the
Gangdese porphyry Cu deposits. In the northern Lhasa block
some younger postcollisional porphyry Mo ± Cu deposits
associated with significant vein-hosted Pb-Zn-W mineraliza-
tion appear to be hosted in the high K adakite-like felsic intru-
sions (Hou et al., 2009; Wang et al., 2014). Mantle-derived
shoshonites were also intruded from a deeper source during
this time (Chung et al., 2005; Searle et al., 2011). Porphyry
Cu-Mo ± Au mineralization appears to be related to both pre-
collisional calc-alkaline and postcollisional adakite-like stages
of magmatism.
Paired granite-mineralization belts of Myanmar
Myanmar contains two major north-south magmatic belts
attributed to the subduction and subsequent closure of Neo-
tethys, and which exhibit contrasting metallogenic character
(Mitchell, 1977; Gardiner et al., 2015a). The westerly Wun-
tho-Popa arc is a discontinuous continental magmatic arc,
comprising Late Cretaceous and Eocene-Miocene grano-
diorites-diorites (Fig. 6; Barley et al., 2003; Mitchell et al.,
2012; Gardiner et al., 2016). It hosts porphyry-type Cu-Au
deposits with associated volcanic rock-hosted epithermal
deposits (United Nations, 1978; Mitchell, 1993). The easterly
Mogok-Mandalay-Mergui belt is marked by a series of Late
Cretaceous-Eocene S-type crustal melt granites (Searle et al.,
2007, 2016). Where these granites intrude the Slate belt, a
low-grade metasedimentary sequence, significant Sn-W min-
eralization is located (Hutchison and Taylor, 1978; Khin Zaw,
1990; Gardiner et al., 2015a).
These belts parallel the Neotethys subduction zone. U-Pb
magmatic and detrital zircon and monazite geochronology
imply that magmatism occurred at intervals from the Late
Cretaceous-Miocene in the Wuntho-Popa arc, and during the
Paleogene in the Mogok-Mandalay-Mergui belt (Barley et al.,
2003; Mitchell et al., 2012; Gardiner et al., 2016). The spa-
tial and temporal relationship between these belts, and their
distinct but consistent metallic endowment over several hun-
dreds of kilometers, has invoked comparison with the South
American Cordillera (Peru/Bolivia; Gardiner et al., 2015a;
Searle et al., 2016). Within the Central Andean margin, proxi-
mal I-type magmatism exhibits Cu-Au-Mo type metallogeny,
while inboard S-type belts host the tin porphyry deposits of
Bolivia and Peru. The early model of Sillitoe (1972), as well as
substantial more recent work, suggests that the petrogenetic
and metallogenic properties of these Andean belts reflect the
influence or otherwise of the mantle, primarily controlled
by distance from the subducting slab, and an increase in the
crustal component of the magmatic source toward the east
(Fig. 9).
The Central Andes has experienced a prolonged tectonic
history, with multiple episodes of magmatism (Pitcher, 1987).
Myanmar, however, represents a geologically simpler environ-
ment that operated over a shorter period of time, resulting in
differences in the timing of styles of mineralization (Gardiner
et al., 2015a, 2016). However, the broad pattern of magmatic
style and age, and of mineralization and geochronology leads
to a simplified petrogenetic and tectonic model, namely that
of an Andean-type setting, a continental magmatic arc sited
above an eastward-dipping subduction zone on the margin of
Neotethys. The following are the principal elements of Myan-
mar metallogeny and their relationship to Neo-Tethyan ocean
closure.
Wuntho-Popa arc, Myanmar (porphyry Cu-Au
and epithermal deposits)
An arcuate belt of Pleistocene calc-alkaline volcanoes defines
the trend of the 100-km-long Wuntho-Popa arc in western
Myanmar. Interpreted as a continental magmatic arc (Mitch-
ell and McKerrow, 1975), it is sited above the Burma seismic
zone, an E-dipping active subduction zone with earthquakes
recorded down to at least 230 km (e.g., Searle and Morley,
2011). At least two major earlier phases of magmatism have
been recorded. Late Cretaceous granodiorite and dacite intru-
sions were followed by Eocene and then Miocene intrusive
and extrusive volcanic rocks (e.g., Barley et al., 2003; Mitch-
ell et al., 2011, 2012; Gardiner et al., 2016). These intrude
a Paleozoic amphibolite-gneissic basement overlain by lime-
stones and pelagic sediments.
Mineralization in the arc is largely confined to the Banmauk-
Wuntho batholith in the north and the Monywa-Mount Popa
region to the south. Close to Wuntho, porphyry-type Cu-Au
deposits, currently uneconomic, have been reported at Shan-
galon, as well as other Au-bearing quartz veining related to the
magmatism. The porphyry Cu-Au deposit at Shangalon has
been dated through zircon U-Pb geochronology to 40 Ma (Gar-
diner et al., 2016). Mineralization at the high-sulfidation Cu
deposit at Monywa, however, is proposed to be of mid-Miocene
in age (13.5 ± 0.2 Ma; Mitchell et al., 2011), which is confirmed
by a U-Pb zircon age from an andesite porphyry at Leptadaung
of 19.9 Ma (Knight and Zaw, 2015; no error provided).
Another well-known gold deposit in Myanmar, and the
country’s largest gold mine, is located at Kyaukpahto, Kawlin
Township, Sagaing Division. Here, Au mineralization is asso-
ciated with stockwork-style quartz veins hosted in silicified
sandstones. Veins comprising pyrite, chalcopyrite, and arse-
nopyrite are best developed in competent silicified sandstone
locally extending into the adjacent mudstones of the lower
mid-Eocene Male Formation (Mitchell et al., 1999; Ye Myint
Swe et al., 2004). These host rocks have undergone intense
hydrothermal alteration and silicification, which appears to be
critical for the genesis of the veining, the latter mainly con-
fined to the silicified sandstone. Fluid circulation and vein for-
mation has been linked to movement on the Sagaing fault in
that NNE-trending extensional faults formed by a component
of dextral strike-slip movement host the stockwork epithermal
Au mineralization in extensional structures (Ye Myint Swe et
al., 2004).

Despite anecdotal reports linking mineralization to the Late
Cretaceous magmatism in the Wuntho region (e.g., United
Nations, 1978), no mineralization has been definitively dated
as relating to this period of magmatic activity. It is neverthe-
less apparent that mineralization (and magmatic activity)
along the Wuntho-Popa arc has been relatively long-lived,
extending from the Paleocene to the Miocene, and the belt
is relatively well endowed with respect to porphyry Cu-Au
and high- to low-sulfidation epithermal styles of mineraliza-
tion. It is also evident that many other examples of Miocene-
aged magmatic-hydrothermal mineralization formed along
the Neo-Tethyan belt, including major deposits such as Sar
Cheshmeh (13.6 Ma) in Iran, Reko Dig (13 Ma) and Saindak
(22.3 Ma) in Pakistan, and Qulong (16 Ma) and Jiama (13 Ma)
in Tibet (Richards, 2015). In the light of the longevity of
magmatism along the Wuntho-Popa arc, the suggestion that
Miocene porphyry and epithermal styles of mineralization in
Tibet and southeast Asia are linked to postcollisional, exten-
sion-related alkaline magmatism (Hou et al., 2009; Shafiei et
al., 2009; Wang et al., 2014; Richards, 2015) requires further
evaluation.
Himalayan-Type Continental Collision Zones
Greater Himalayan sequence
The stratigraphy, structure, and metamorphic-magmatic
evolution of the Himalaya is reasonably well-constrained, as
a result of field studies, combined with detailed structural,
metamorphic, thermobarometric, and U-Pb geochronologi-
cal studies (see reviews by Hodges, 2000; Yin and Harrison,
2000; Searle et al., 2010b). Figure 10 shows a profile, though
approximately 70 km of Himalayan crust, with folded and
thrusted upper crustal sedimentary rocks of the North Indian
margin underlain by the regional Barrovian metamorphic
I - igneous source
S - crustal
sedimentary source
Regional
metamorphism
Moho
Tectonic Setting
Oceanic plate
trench/
fore-arc
Andean margin Plateau
Crustal thickened
mountain belt
Western Cordillera Eastern CordilleraAltiplanoAndes:
Myanmar: Monywa - Popa arc Mandalay-Mogok-
Mergui belt
Granites: I - types (hbl bt) S-types (bt, ms, tur, grt)
Volcanics: Calc-alkaline andesites etc. No volcanic rocks
Mineralization: Cu-Au-Mo-Pb-Zn Sn-W-U-Th
andesitic volcanoes
Future
Sagaing fault
oceanic plate
oceanic subduction zone
Fig. 9. Tectonic profile across an Andean-type margin, comparing the structural positions of the paired granite belts of the
Andes and Myanmar. Abbreviations: bt = biotite, grt = garnet, hbl = hornblende, ms = muscovite, tur = tourmaline

316 SEARLE ET AL.
rocks of the Greater Himalayan middle crust. The lower crust
is the underthrust basement of the Indian shield. A major
episode of precollision deformation was synchronous with a
Late Cretaceous-Paleocene phase of obduction of large ophi-
olitic thrust sheets onto the Indian passive margin sequence.
Only a few remnant ophiolites are preserved at the highest
structural levels of the Tethyan zone, the best example being
the Spontang ophiolite in Ladakh (Fig. 3; Corfield and Searle,
2000; Corfield et al., 2001). The northern part of the Indian
plate mid-lower crust exposed in the Tso Morari dome in
Ladakh and along the Kaghan valley, north Pakistan (Fig. 3)
shows an early ultrahigh-pressure metamorphism recorded by
coesite-bearing eclogites (e.g., O’Brien et al., 2001; St-Onge
et al., 2013). These ultrahigh-pressure assemblages have been
overprinted by later kyanite- and sillimanite-grade metamor-
phism during the main phase of crustal thickening in the late
Eocene-early Miocene.
Deformation of the Indian plate resulted in folding and
thickening of upper crustal sedimentary units (the Tethyan
Himalaya), whereas middle and lower crustal lithologies
along the Greater Himalaya were buried and heated as a
result of crustal thickening (Fig. 4). The metamorphic core
of the Himalayan range, the Greater Himalayan sequence,
experienced a regional Barrovian-type metamorphism up to
kyanite-grade P-T conditions (560°–630°C; 10–12 kbars, 35-
to 40-km depth of burial) between ca. 35 to 30 Ma, which was
70
60
50
40
1
~0.5
30
20
10
0
km GPa
North Indian plate margin
Himalaya
Indian continental
lithosphere mantle
Paleo-Eocene limestones
Lamayuru allochthonous
Tethyan sedimentary rocks
Folded and thickened
Permian-Mesozoic
shelf carbonates
Panjal volcanic rocks
Folded and thickened
Palaeozoic sedimentary rocks
South Tibetan Detachment
Main Central Thrust
Main Himalayan Thrust
Indian lower crust granulites
Leucogranites
PEGMATITIC
U, Sn
sillimanite gneisses
+ migmatites
kyanite gneisses
ophiolite
2
80
STD
MHT
Moho
MCT ZONE
ky
sill + ms
st
grt
Fig. 10. Profile through the Himalayan crust, showing major rock types with structural depth.

followed by decompression and heating leading to regional
sillimanite- and cordierite-grade metamorphism, migmatiza-
tion, and formation of leucogranite melts between ca. 24 to
19 Ma (620°–700°C; 4–7 kbars, 15- to 20-km depth of burial;
Searle et al., 2010b). Melting along the Greater Himalaya
sequence began probably around 35 m.y. ago, resulting in the
earliest kyanite-bearing migmatites at ca 700°C and 7 kbars,
followed by later sillimanite- and cordierite-bearing melts
recording higher temperatures but lower pressures. These
extensively developed melt phases, commonly accompanied
by pegmatites emanating from the top of leucogranite intru-
sions, are large-ion lithophile element (LILE) enriched, but
typically devoid of mineral deposits, with the exception of
gem-quality tourmaline with garnet and muscovite.
This structural and thermal evolution is consistent along
the 2,000-km length of the central Himalaya (e.g., Searle et
al., 1999, 2006; Walker et al., 2001; Godin et al., 2006). How-
ever, in the orogenic syntaxes of Nanga Parbat (NW syntaxis;
Fig. 3) and Namche Barwa (NE syntaxis), the rocks have been
through the same Cenozoic thermal history as the rest of the
Himalaya, but show evidence of an additional, younger Plio-
cene-Quaternary high-grade metamorphism and migmatiza-
tion event (Zeitler et al., 2001; Booth et al., 2008; Crowley et
al., 2009). The youngest metamorphic and structural episodes
dated in the syntaxes (Pliocene-Quaternary) are character-
ized by extremely rapid exhumation rates, and may reflect
processes operating at depth beneath the northern Himalaya,
Karakoram, and south Tibet today.
Mogok metamorphic belt, Myanmar
The Mogok metamorphic belt extends for over 1,500 km from
the east Himalayan syntaxis to the Andaman Sea. It comprises
a middle and lower crustal section exhumed by compres-
sional deformation prior to dextral strike-slip faulting along
the Sagaing fault. The belt includes precollision I-type gran-
ite magmatism, including hornblende-bearing granodiorites
dated by U-Pb zircon geochronology as Jurassic-Cretaceous
(Barley et al., 2003; Mitchell et al., 2012). The Mogok belt also
includes postcollisional regional metamorphic rocks up to sil-
limanite grade. U-Pb monazite dating suggests two phases of
metamorphism, one prior to 59.4 Ma, the age of crosscutting
biotite granite dikes, and the other between 37 to 29 Ma (Searle
et al., 2007). Localized partial melting resulted in the formation
of tourmaline + garnet leucogranitic melt pods at 24.5 ± 0.7 Ma
(Searle et al., 2007), whereas the sizeable Kabaing granite that
intrudes the marbles has been dated at 17 Ma (Gardiner et al.,
2016). Around the town of Mogok, high-temperature marbles
have been intruded by alkali syenite intrusions, and contain
abundant rubies and sapphire gemstones (Searle et al., 2016).
Tethyan Mineral Zones
Tin-tungsten belts (Malaysia-Thailand-Myanmar)
The granite belts of southeast Asia collectively comprise one
of the world’s greatest metallotects of Sn and major, albeit
localized, W. The region has been the dominant global Sn
producer, accounting for some 54% of historic production
(Schwartz et al., 1995). Three principal belts are identified
(Fig. 11): the Western province, or Mogok-Mandalay-Mergui
belt (central Myanmar and Thailand; Fig. 6); the West Malaya
Main Range plutons (eastern Myanmar, western Thailand,
and western Malaysia peninsula); and the eastern Malay plu-
tons (eastern Myanmar, central Thailand, and eastern Malay
peninsula; Hutchison, 1977; Cobbing et al., 1986, 1992; Khin
Zaw 1990; Sone and Metcalfe, 2008; Searle et al., 2012; Ng
et al., 2015a, b; Gardiner et al., 2015b). These granite belts
are the magmatic expressions of the closure and suturing of
Paleo-Tethys and Neotethys, and were thus emplaced during
multiple time periods including the Early Triassic (Eastern
province, Malaysia), Late Triassic (western Main Range gran-
ites, Malaysia; Ng et al., 2015a, b), Late Cretaceous-Eocene
(SW Myanmar; Gardiner et al., 2016), and Paleogene (Phuket,
SW Thailand; Searle et al., 2012).
The Paleo-Tethyan suture is represented by the Bentong-
Raub suture zone, which separates the Main Range tin gran-
ites of the Western province from the dominantly subduction
related I-type granites of the Eastern province of Malaysia
(Fig. 11). In Malaysia the most prolific tin mineralization is
associated with the western Main Range province granites
with U-Pb zircon ages spanning 227 to 201 Ma, although
lesser but nevertheless still significant Sn mineralization also
occurs in the subduction-related I-type granites of the East-
ern province, which have U-Pb zircon ages spanning 289 to
220 Ma (Ng et al., 2015b). Thus, tin granites crop out across
the Malay peninsula on both sides of the suture. In Thailand
and the Malay peninsula, tin is principally mined from placer
deposits both onshore and offshore, reflecting the high degree
of erosion of these granites.
The Mogok-Mandalay-Mergui belt in eastern Myanmar is
related to crustal thickening following the closure of Neo-
tethys (Searle et al., 2007, 2016; Gardiner et al., 2015a). It
comprises a mixture of I- and S-type granites (Cobbing et
al., 1986; Khin Zaw, 1990; Barley et al., 2003; Mitchell et al.,
2012), although magma compositions tend to evolve toward
more peraluminous S-type granites with time. Magmatic ages
range from Late Cretaceous to Eocene (Barley et al., 2003;
Searle et al., 2007, 2016), with many of the tin deposits related
to granites crystallizing at 70 to 50 Ma (Aung Zaw Myint et
al., 2016; Gardiner et al., 2016), which we interpret as rep-
resenting the timing of mineralization. These S-type granites
are likely the product of melting of a crustal protolith. Tin
granites thus crystallized prior to the main phases of regional
metamorphism along the Mogok belt, which occurred during
the Late Cretaceous-Paleocene and again in the Eocene-early
Miocene (Searle et al., 2007, 2016). The tin granites in Myan-
mar are significantly younger (Cretaceous to Paleogene) than
those of the Malaysian belts and are substantially less eroded.
Accordingly, there are many more primary deposits found in
the region, including the historic mines focused around the
port town of Dawei (Fig. 6). The region is also substantially
more tungsten specific than Malaysia, and hosts the famous
W-Sn Mawchi mine, 250 km northeast of Yangon (Fig. 6).
Tin mineralization in southern Myanmar is focused where
the Cretaceous-Eocene S-type granites intrude the Slate
belt, a predominantly late Paleozoic succession of low-grade
metasedimentary units, pebbly mudstones with occasional
limestones, collectively defined as the Mergui Group (Mitch-
ell, 1992). Primary tin mineralization is found as cassiterite-
hosting quartz veins and as pegmatites, either intruding the
country rock, or within the upper parts of the granite bodies.

318 SEARLE ET AL.
Tungsten is spatially associated with the tin mineralization,
commonly as wolframite, and more rarely as scheelite.
Origin of tin granites
Although most Sn-W deposits are hosted in peraluminous
S-type granites, in the Tethyan belts and elsewhere, fraction-
ated I-type granites may represent the preferred host rocks
to LILE mineralization (Groves and Bierlein, 2007; Ng et al.,
2015a). Although significantly enriched, the highly peralumi-
nous Himalayan leucogranites are not associated with signifi-
cant Sn, or LILE mineralization, whereas the I-type granites
of the Malaysian Eastern province are relatively Sn rich. In a
recent review, Romer and Kroner (2016) proposed that the
formation of Sn and/or W mineralization was the result of
three main processes: source enrichment, magma accumu-
lation, and subsequent concentration of metals by fractional
210 Ma
220 Ma
230 Ma
250 Ma
260 Ma
104°100° 101° 102° 103°99°E
104°
1°
6°
5°
4°
3°
2°
7°N
1°
6°
5°
4°
3°
2°
7°N
100° 101° 102° 103°99°E
Bentong-Raub suture zone
West Malaya Main Range plutons
Alkali syenites
Eastern Malaya plutons
50 km0
THAILAND
Main Range batholith Benom
Kapal batholith
Perhentian
Redang
Boundary Range batholith
Bentong-Raub
suture
Tioman
Langkawi
Is.
Pulao
Tuba
Koh
Tarutao
Singapore
Kuala Lumpur
Melacca
Kinta Valley
Penang
Noring
Stong
Ipoh
Gulf of
Thailand
StraitsofMelacca
80 ± 1 Ma
Fig. 11. Geologic map of the Malay peninsula, showing the paired magmatic belts of the Main Range tin granites in the west,
and the eastern Malay I-type granites in the east separated by the Paleo-Tethyan Bentong-Raub suture zone (after Searle et
al., 2012; Ng et al., 2015b). Age contour lines are from regional U-Pb zircon data from Ng et al. (2015b). The 80 ± 1 Ma age
of the Tioman island granite is from Searle et al. (2012).

crystallization and hydrothermal processes. The model calls
upon an inherited metal endowment in the source region(s)
a factor that is then used to explain the diachronous nature
of Sn deposits that occur at multiple times during orogenic
events and also across different terranes—such is very much
the case in the Tethyan belts of southeast Asia.
Skarn Au-base metal deposits (Shante, Myanmar,
and Mengapur, Malaysia)
The Shante gold district of Myanmar lies 50 km south of
Mogok (Fig. 6), within the high-temperature marbles of the
Mogok metamorphic belt. Skarn-type Pb-Zn ± Au mineral-
ization is quartz-vein hosted within the marbles. The Kwin-
thonze mine, near Thabeikkyin, is a marble-hosted Au-base
metal sulfide deposit, interpreted as skarn type, and through
spatial association interpreted as related to the intrusion of the
Kabaing Granite (Tin Aung Myint et al., 2014). The Kabaing
Granite has been dated through zircon U-Pb geochronology
to ca. 17 Ma (Gardiner et al., 2016), thereby providing some
age constraints on this mineralization. It is thus interpreted as
related to the late stages of Mogok metamorphism.
Skarn-hosted Cu-Au mineralization is also know from east-
central Malaysia. This deposit is hosted by Permian calcareous
sediments that have been intruded by an undated, but likely
Triassic-aged, adamellite body that is also linked to extrusive
rhyolite and tuff (Snowden Report, 2012). Both garnet- and
pyroxene-rich skarns host vein sulfide mineralization that is
dominated by pyrrhotite and chalcopyrite. Fluid inclusion
studies suggest that sulfide mineralization is related to retro-
grade processes involving a component of low-salinity mete-
oric fluids possibly implicated in the precipitation of metals
(Heng et al., 2003). The Mengapur Cu-Ag system occurs
within the so-called Central belt of Malaysia, occupying a posi-
tion intermediate between the Sn-W-dominant, S-type Main
Range and the I-type Eastern province. The Central belt in
Malaysia contains numerous gold and base metal deposits, but
its metallogenic significance and relationship to the surround-
ing, better defined belts is not well understood.
Orogenic gold (Mogok-Mandalay-Mergui belt, Myanmar,
and peninsular Malaysia)
In central Myanmar, prospective Au mineralization is found as
quartz vein and pyrite stringers within the low-grade metasedi-
mentary Slate belt (Mitchell et al., 2004). Mineralization is
found extending in a belt for over 100 km around Mandalay. The
style of mineralization is typical of turbidite-hosted orogenic-
style Au; however, neither its age nor genesis is well constrained.
Reported age determinations from studies of the Modi-Taung-
Nankwe and the Meyon deposits range from the Jurassic to
Paleogene (Mitchell et al., 2004; Zaw Naing Oo and Khin Zaw,
2009), and reflect the polyorogenic history of the region and the
difficulty in ascribing gold deposits to a particular event.
Orogenic-style gold is typically associated with the wan-
ing stage of orogeny. Mineralization is focused along major
deep-penetrating shear zones, along which aqueous-carbonic
fluids derived from midcrustal metamorphism during crustal
thickening circulate to precipitate gold ores at crustal levels
that broadly equate to greenschist-amphibolite grades (e.g.,
Groves et al., 1998). The genesis of the Slate belt Au is pos-
sibly related to the Himalayan orogeny (closure of Neotethys)
in the Eocene, although some workers (Mitchell et al., 2004)
believe that older metamorphic overprints were related to
the Late Triassic-Jurassic Indosinian orogeny (closure of
Paleo-Tethys).
Orogenic gold deposits also occur in peninsular Malaysia
where mineralization is almost certainly related to the older
orogenic cycle. Significant gold deposits at Raub, Penjom, and
Selinsing all occur close to the Bentong-Raub suture in the
Central belt of Malaysia. With many similarities to the Slate
belt gold deposits of Myanmar, but located in an entirely dif-
ferent magmatic arc, the existence of widespread orogenic
gold styles of mineralization point to a pervasive interplay
between the tectonic and magmatic evolution of the region
and circulation of auriferous metamorphogenic fluids.
Intraplate Alkaline Magmatism
Alkaline magmatism is common during the early stages of
continental rifting (e.g., East Africa, Red Sea) and the later
stages of orogenesis (e.g., lamprophyre dikes; adakite-like and
shoshonitic dikes in Tibet), or even long after mountain build-
ing (e.g., kimberlites). Lamproites and lamprophyres are syn-
to late-collisional alkaline intrusions that commonly intrude
mountain belts during the later tectonic history.
Syenites, alkali peridotites
In the Mogok metamorphic belt of Myanmar several syenite
bodies have been intruded into the regional metamorphic
rocks that are dominated by thick marbles, some of which
are rich in rubies and sapphires. Pressure-temperature condi-
tions of metamorphism were around 600° to 680°C and 4 to 6
kbars in the rare pelites in the Mogok belt (Searle et al., 2007).
There is little evidence of large-scale folding and thrusting as
seen elsewhere along the Himalaya, so it appears that crustal
thickening was not an obvious process involved in regional
metamorphism. An additional source of heat is required to
obtain the high temperatures needed for metamorphism in
the Mogok belt, which may have been from mantle-sourced
syenite intrusions (Searle et al., 2016). Whereas rubies are
present throughout some marble bands, sapphires appear to
be mainly located along syenite-marble contact zones, sug-
gesting a link between syenite-derived heat source and mar-
ble host rock. In a few localities alkali peridotites represent
the deepest part of the syenite intrusion, suggesting internal
differentiation and a magma origin related to highly enriched
subcontinental mantle lithosphere.
Mantle-derived lamproites, shoshonites
In addition to the lower crust-derived adakite-like intrusions,
the Tibetan plateau hosts numerous mantle-derived shosho-
nite dikes (Chung et al., 2003, 2005). Potassium-rich shosho-
nites and subordinate sodium-rich lavas were erupted across
the Tibetan plateau between 50 and 10 Ma (Chung et al.,
2003, 2005; Fig. 12). These shoshonitic magmas require a hot,
hydrous (phlogopite-bearing) and weak mantle lithosphere
source. Felsic and mafic granulite and pyroxenite xenoliths
entrained in 17 to 14 Ma ultrapotassic dikes suggest very high
pressures and temperatures (1,330°–1,130°C; 26–22 kbars;
Chan et al., 2009). Using both surface geology and xenoliths in
the dikes, Searle et al. (2011) proposed a profile through the
75-km Tibetan crust (Fig. 13). The youngest magmatic rocks

320 SEARLE ET AL.
Fig. 12. (a). Simplified geologic map of the Tibetan plateau, showing the distribution in space and time of postcollisional
adakite and shoshonite intrusions, after Chung et al. (2005). Abbreviations: BNS = Bangong-Nujiang suture zone, ITS =
Indus-Tsangpo suture zone, MCT = Main Central thrust, STDS = south Tibetan detachment sytem. (b). Space-time diagram
showing variation of Tibetan magmatism across the Tibetan plateau. See Chung et al. (2005) for sources of data.

0
km
10
20
30
40
50
60
70 2
1
~1.7
~0.4
GPa Adakitic
volcanics
Shoshonitic
volcanics
80
90
100
Sedimentary rocks
Greenschistsshallow
reservoir
Adakite
Amphibolites
Tonalite-
Granodiorite
Felsic granulites
UPPER
CRUST
MIDDLE
CRUST
LOWER
CRUST
ultra-potassic
lamproites
Breccias, Quartz veins
Porphyry Cu-M0
granites ± Au
bt- hbl-
lamprophyre
dykes
hbl + pl ± cpx
granodiorites
cpx + grt + pl ± opx
± ky
grt + opx + pl + kfs
+ bt + ky + qtz
crd + sill + opx
grt + cpx ± hbl
Primitive K-rich
mantle melts
MOHO
MANTLE
harzburgite
Eclogites - grt + cpx
Ultramafic restites - hbl + bt
Mafic UHT- HP
granulites
lherzolites
dunite
ol + opx
ol + opx + cpx
ol
b c
a
Fig. 13. (a). Schematic crustal profile through the crust of south Tibet, after Searle et al. (2011). Mineral compositions of
lower crust granulites and eclogites are derived from xenoliths within the Cenozoic shoshonite dikes (Chan et al., 2006).
(b). Field photograph of typical adakitic dike intruding the Lhasa block. (c). Shoshonite dike from near Xigase, south Tibet.
Abbreviations: bt = biotite, cor = cordierite, cpx = clinopyroxene, grt = garnet, hbl = hornblende, kfs = K-feldspar, ky = kya-
nite, ol = olivine, opx = orthopyroxe, pl = plagioclase, sill = sillimanite.

322 SEARLE ET AL.
in Tibet are a swath of potassium-rich shoshonitic volcanic
rocks along the KunLun mountain range in the far north of
Tibet. The spatial and temporal distribution of volcanic rocks
across the Tibetan plateau suggest the progressive northward
shift of a hot mantle source, as cold Indian lithosphere pro-
gressively underthrust Tibet from south to north, from 50 Ma
to the present day (Searle, 2015).
Placer Deposits
The largest gold deposits in the world are derived from
secondary concentrations of detrital gold into sedimentary
basins accumulating erosional debris from adjacent island-
arc terranes or collisional mountain belts (e.g., Witwatersrand
Basin). Detrital fluviatile gold deposits along the upper Indus
valley are almost certainly derived from the Ladakh island
arc and batholith to the north. Gold is presently mined from
recent basins and river systems along the Shan Scarp in Myan-
mar. These are likely derived from erosion of the Slate belt,
where in situ Au occurs in orogenic vein systems such as at
Modi Taung (Fig. 6; Mitchell et al., 2004). Some gemstones,
notably rubies, spinel, sapphire, and rare diamond, are mined
from placer deposits along the Mogok metamorphic belt.
Far more widespread than gold or gem placers in southeast
Asia, however, are the vast accumulations of placer tin miner-
alization that have formed in a variety of fluvial, fluvio-deltaic,
and shallow-marine settings. The southeast Asian tin belt has
been almost entirely mined from placer deposits in alluvial
and fluvial basins across the Malay peninsula as well as off-
shore southwestern Thailand in the Phuket area. The tin was
derived from erosion of the Triassic Main Range granites in
the western Malay peninsula (Ng et al., 2015a, b) and S-type
granites from the Phuket western Thailand belt that may be as
young as Paleocene in age (Searle et al., 2012).
Conclusions
The record of mineralization formed during the closure of
Paleo-Tethys (the Indosinian orogeny) is generally not well
preserved. By contrast, Neo-Tethyan Himalayan orogenesis
is better preserved and understood than earlier cycles and,
importantly, the diversity and preservation of mineralization
during closure of Neotethys has resulted in the formation of
very significant metallogenic belts. We summarize Tethyan
orogenesis on a regional basis where well-defined and chrono-
logically constrained magmatic events can be identified (Fig.
14). The broad metallogenic framework, however, is markedly
different on either side of the collision zone and is presented
on this basis below.
Metallogeny south of the Neo-Tethyan suture
The Himalayan orogenic cycle and its metallogenic affinities
south of the Neo-Tethyan suture can be summarized in terms
of well-defined orogenic stages, including precollisional ophi-
olite obduction, collisional crustal thickening, metamorphism,
and partial melting. The precollisional stage is marked by Late
Cretaceous-Paleocene ophiolite formation and obduction.
The mantle portions of ophiolite complexes are dominated by
magmatic concentrations of Cr, Ni, and PGM, whereas shal-
lower, crustal sequences preserve concentrations of chalco-
philic metals (Cu-Zn) associated with ocean-water circulation
and venting. In the western Himalaya a large-scale island arc,
the Kohistan island arc, has been obducted southward onto
the northern margin of the Indian plate approximately at the
same time as ophiolite complexes preserved in the Ladakh
Himalaya (Searle at al., 1997b; Corfield and Searle, 2000).
Subduction of the leading edge of the downgoing Indian con-
tinental crust led to ultrahigh-pressure eclogite facies meta-
morphism along the northern margin of the Indian plate at
Kaghan (Pakistan) and Tso Morari (Ladakh; ~57–47 Ma).
Few known mineral deposits of any significance characterize
this phase.
Crustal thickening and shortening along the Himalaya
resulted in kyanite-grade metamorphism (~40–30 Ma) and
partial melting, and is likewise characterized by few known
mineral deposits of any significance. Sillimanite-grade
metamorphism was accompanied by decompression melt-
ing, formation of migmatites and leucogranites, and south-
directed extrusion of the ductile midcrust by channel flow
(~24–15 Ma). This stage is characterized by the formation of
anatectic, peraluminous granite melts significantly enriched
in granitophile elements, but is of little significance as a metal-
logenic province. Southward-propagating thrusting along
the Lesser Himalaya formed a subcritical wedge with active
underthusting of India beneath the Himalaya. The downgoing
slab in the Himalayan context (Indian plate) is also featured
by a lack of processes (magmatism, focused hydrothermal
fluid circulation, etc.) that typically give rise to significant
mineral deposits.
Metallogeny north of the Neo-Tethyan suture
For the Asian side of the India-Asia collision zone in the
Karakoram and Pamir ranges, as well as across the Lhasa and
Qiangtang blocks of Tibet (i.e., the upper, overriding plate),
the orogenic and metallogenic framework is very different
and can be summarized as follows. A phase of Triassic-Early
Jurassic subduction, crustal thickening, and regional meta-
morphism resulted in the Indosinian orogeny that spanned
central Asia from Afghanistan and the Pamir region across
central Tibet to eastern Myanmar-Thailand and into Malaysia.
The tin granite belts of Malaysia and southwestern Thailand,
which young progressively from east to west, are associated
with Permian to Late Triassic granites that formed during clo-
sure of Paleo-Tethys along both sides of the Bentong-Raub
suture (Searle et al., 2012; Ng et al., 2015a, b). This repre-
sents a major metallogenic province dominated by Sn-W min-
eralization (now significantly eroded and reconcentrated into
substantial paleoplacer deposits, both onshore and offshore of
Malaysia-Thailand).
Pre-India-Asia collision crustal thickening in an Andean-
type setting over a period spanning the Early Jurassic–early
Eocene, occurred along the Kohistan-Ladakh-Gangdese
batholith (~198–49 Ma; Chung et al., 2005; Chu et al., 2006).
This major magmatic event across the entire collision zone,
spanning some 2,500 km, does have some significant porphyry
Cu-Au-Mo deposits hosted in typical calc-alkaline granitoids
ranging from Jurassic to Eocene in age (Tafti et al., 2001; Qu et
al., 2009). However, work by Wang et al. (2014a, b) and Rich-
ards (2015) indicates that factors such as magma water con-
tent and magmatic oxidation state, which play a role in terms
of metal concentration and ore-forming processes, were not
optimal for the formation of porphyry and epithermal styles of

mineralization along the central portion of the batholith. Else-
where, toward the east in Tibet, younger Miocene adakite-
like magmas were wetter, more oxidized, and more conducive
to the formation of significant magmatic-hydrothermal styles
of mineralization. Beyond the eastern syntaxis, magmatism
during the Cretaceous and Paleogene was more peralumi-
nous, giving rise to significant granite-hosted Sn-W mineral-
ization along the Mogok-Mandalay-Mergui arc of Myanmar.
Calc-alkaline magmatism occurred closer to the leading edge
of subduction along the Wuntho-Popa arc in Myanmar, giving
0
10
20
30
40
50
100
Ma
150
200
250
QIANGTANG
EAST
HIMALAYAN
SYNTAXISNORTH
MOGOK
BURMA
THAILAND MALAYA
WEST EAST
LHASA
TIBET
SOUTH
CRETACEOUS
CENOZOIC
PALEOGENENEOGENE
JURASSICTRIASSIC
MIDDLEMIDMIDDLEUPPERUPPERUPPERPALOLIGPLEOCENEMIOCENELLOWERLOWER
ECLOGITE
ECLOGITE
Jade
QIANGTANG-LHASA
COLLISION
SUMDA SUTURE
BENTONG-RAUB SUTURE
Danba
Danba
GangdeseGangdeseGang
dese
Shoshonites
Takena Fm.
INDIA - ASIA SUTURE
Metam
Metamorphism
Metamorphism
orphism
Mt. Popa
volcano
Payangazu
Sedawgyi
Mae Klang
Lansang
Klong Marui/Ranong
Thabsila
Klong Marui
Bhumipol
lake
Doi Inthanon
Ranong
Phuket
zir rims
Lansang
Klong Lan
Tioman Is.
Klong Lhan
Doi Inthanon
protolith
Main Range
granites
West Malaya
Peraluminous
I-type granites
East Malaya
Phuket
zir core
Kyaushe
Mandalay
MEC
Sedo
Kyanikan
Belin dyke
Nattaung
Mokpalin
Monywa-
Salingyi
Kyaushe
Yebokson
diorite
Kyanikan
Mandalay
Belin
Linzizong
Fig. 14. Mesozoic-Cenozoic time chart showing age ranges of metamorphic, magmatic, and mineralization processes. Blue
line represents youngest marine sedimentary rocks and timing of suture zone closure; orange colors represent I-type (calc-
alkaline) magmatism; yellow colors represent periods of regional Barrovian-type metamorphism; pink lines represent S-type
(more peraluminous) granites associated with postcollisional crustal thickening; green line represents age range of mantle-
derived shoshonites.

324 SEARLE ET AL.
rise to significant porphyry and epithermal mineral deposits
(Gardiner et al., 2015a).
Postcollisional crustal thickening in Tibet resulted in lower
crust kyanite- and sillimanite-grade metamorphism during the
Cenozoic, exhumed in selected areas of southeast Tibet (Palin
et al., 2013). This event was not characterized by any known
mineral deposits of significance. In Myanmar, however, this
stage of mainly Paleogene metamorphism hosted many gem-
stones along the Mogok belt, including world-class ruby and
sapphire-bearing marbles. Searle et al. (2007) used U-Th-Pb
dating to define two main phases of high-temperature meta-
morphism: a pre-59 Ma event and a later sillimanite + mus-
covite event at least from 37, possibly from 47 Ma to 29 Ma.
Postcollisional lower crustal melting resulted in adakite-like
rocks, and mantle melting-generated shoshonites (Chung et
al., 2005, 2009; Lee et al., 2009; Wang, Q. et al., 2010; Wang,
R. et al., 2014a, b). This event has assumed increasing metal-
logenic significance as mineral deposits and their host rocks
throughout the region are more accurately dated by Re-Os
and U-Pb zircon techniques. It is increasingly evident that
the period between ca. 22 and 12 Ma (peaking at around 15
Ma) is characterized by concentration of very significant por-
phyry Cu-Au deposits mainly along the eastern portions of the
Lhasa block, but less so in the western portions. Magmatism
during this part of the cycle has been attributed to slab break-
off and melting of a fertile protolith (Chung et al., 2005) to
form numerous, world-class porphyry and epithermal depos-
its (Hou et al., 2009; Wang et al., 2014a, b; Richards, 2015).
Oligocene-Miocene crustal thickening and regional meta-
morphism along the Karakoram (Searle et al., 2010a) and
Pamir (Stearns et al., 2013) is characterized by few known
mineral deposits of any significance. Gem-quality tourmaline
and aquamarine (beryl) in the Karakoram Range of north Pak-
istan are associated with young (<5 Ma) pegmatite dikes in
sillimanite-grade gneiss domes. It is likely that extreme crustal
thickening and high-grade amphibolite, granulite, and eclog-
ite facies regional metamorphism in the west (Karakoram,
Pamir) and east (SE Tibet) was not conducive to preservation
of major mineral deposits, such as seen along the Gangdese
belt of central southern Tibet.
Similar to the Andes, the Tethyan orogenic belts represent
a vast region of plate subduction, accretion, magmatism, and
associated tectonism that ultimately consumed a major por-
tion of oceanic crust and gave rise to the creation of continen-
tal crust from the late Paleozoic to the present. These events
yielded the conditions that favored the formation of many
different styles of ore deposits, providing these regions with
a substantial endowment of mineral wealth. Although the
overall pattern of events that link crustal evolution to metal-
logeny are well understood, the details of where and why the
biggest mineral deposits occur, and the controls of metal fer-
tility and specificity in magmas, are not. The Tethyan belt is
a metallogenic province that offers considerable promise for
the discovery of new deposits, as well as answers to the many
questions that remain.
Acknowledgments
We appreciate the insights gained from numerous discussions
and field trips with Andrew Mitchell and Chris Morley, and
drafting of diagrams by Dave Sansom. The manuscript was
substantially improved by the detailed reviews provided by
Doug Kirwin, Graham Begg, and editors Jeremy Richards
and Yongjun Lu.
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Tectonic Processes and Metallogeny along the Tethyan Mountain Ranges of the Middle East and South Asia (Oman, Himalaya, Karakoram, Tibet, Myanmar, Thailand, Malaysia)

Tectonic Processes and Metallogeny along the Tethyan Mountain Ranges of the Middle East and South Asia (Oman, Himalaya, Karakoram, Tibet, Myanmar, Thailand, Malaysia)

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