intrusive plutonic rocks

2. INTRUSIVE VOLCANIC ROCKS
BY
T.VENKATESH,
1ST YEAR,M.SC.GEOLOGY,
DEPARTMENT OF GEOLOGY.

3. CONTENT
• INTRODUCTION
• BATHOLITHS
• LACCOLITHS
• PHACOLITHS
• LOPOLITHS
• SILLS
• DYKES
• CONCLUSION

4. INTRODUCTION
there are two types rocks which
is produced by the
vulcanicity.they are,
1.extrusive rocks
2.intrusive rocks

6. INTRODUCTION
• Major intrusive rocks are,
• Batholiths,laccoliths,phacoliths,lopoliths,sills,
dikes, etc.
• When gases & vapour are not erupted
strongly,the ascending magmas to not erupt
as lava rather these are intruded in below
crustal surface and after solidification
assume intrusive rocks.

7. BATHOLITH:
Description: It is a large, irregularly shaped
reservoir of magma.
Formation: Magma intrudes into a large
chamber beneath the surface of the earth. It
cools and solidifies at a very slow rate there.
It is commonly composed of coarse-grained
rocks (e.g., granite)
Batholith cools and solidifies, later to be
exposed at the surface through erosion

9. LACCOLITH:
 Description: It is a dome like feature
between bedding planes.
 Formation: Magma intrudes between bedding planes,
but its progression is blocked by a structure. The
magma pushes up the rock layer above it. It cools and
solidifies at a very slow rate there.
 Acid rocks are more common than basic rocks in
laccoliths.

11. PHACOLITH:
A phacolith is a pluton parallel to the
bedding plane.
It is typically lens-shaped pluton that
occupies either the crest of an anticline or
the trough of a syncline.
In rare cases the body may extend as a
sill from the crest of an anticline through
the trough of an adjacent syncline, such
as cross section.

13. LOPOLITH:
A saucer- or lens-shaped body of intrusive
igneous rock, formed by the penetration of
magma between the beds or layers of existing
rock and subsequent subsidence beneath the
intrusion.
It is believed that lopoliths are formed when
magma which has intruded into the earth’s
crust draws close to the earth’s surface and the
sedimentary rock underlying the lopolith sinks
in the area of the magma chamber.

15. SILLS:
Description: It is a horizontal sheet like
feature between bedding planes.
Formation: Magma intrudes between bedding
planes. It cools and solidifies at a very slow rate
there.
 Sills can be confused with solidified lava flows;
however, there are several differences between
them, i.e., intruded sills will show partial melting
and incorporation of the surrounding country
rock.

17. DYKES:
Description: It is a vertical or diagonal wall like
feature cutting across bedding planes.
Formation: Magma intrudes into a line of
weakness cutting across beddingplanes
vertically or at an angle. It cools and solidifies
at a very slow rate there.
Dikes can be either intrusive or sedimentary in
origin. For example, when molten rock intrudes
into a crack then crystallizes, it is an igneous
dike. When sediment fills a pre-existing crack,
it is a clastic dike.

19. CONCLUSION:
Intrusive vulcanicity occurs when the
magma enters and solidifies in lines of
weakness or chambers in the earth's
crust.
Many mountain ranges, such as the Sierra
Nevada in California, are formed mostly by
intrusive rock, large granite (or related
rock) formations.

20. REFERENCE:
https://en.wikipedia.org/wiki/Intrusion
myweb.facstaff.wwu.edu/talbot/cdgeol/Ign
eous/Intrusive
Physical geography by K. Bharadhwaj.
http://www.weebly.com/?
utm_source=internal&utm_medium=footer
&utm_campaign=2