This document discusses Mississippi Valley-type (MVT) deposits, which are important sources of lead and zinc found hosted in carbonate rocks. MVT deposits form from hydrothermal fluids emanating from deep shale source rocks that are overpressured. These fluids flow upward through aquifers, depositing zinc, lead, and sometimes fluorite minerals in fractures or pores in carbonate host rocks. MVT deposits are classified into zinc-dominant, lead-dominant, and fluorite-dominant subtypes based on primary mineral associations. Factors influencing MVT deposit formation include porosity in the host rock and sufficient quantities of trace elements in migrating fluids. Examples of MVT deposits in Pakistan include occurrences in Jurassic

1. Muhammad Bilal (23)
MISSISSIPPI VALLEY TYPE DEPOSITS
3/11/2018MVT DEPOSITS 1

2. CONTENT
• Introduction
• Host rock
• Source rock (fluid flow)
• 3 sub types
• Origin factors
• Occurrence in Pakistan
3/11/2018MVT DEPOSITS 2

3. INTRODUCTION
• Leading source of Lead and Zinc
• Type locality: Mississippi valley mines southeast USA
• The first exploration and mining of such deposits was by Roman Empire 200BC
• Lead was there major source of metal especially used for water transportation by Lead
pipes, which is also considered the major Cause of fall of the Empire, as Lead particles
dissolved in water are poisonous (Gilfillan, 1965).
3/11/2018MVT DEPOSITS 3

4. INTRODUCTION
• These are Lead-zinc deposits of epigenetic nature.
• Hosted in Carbonate Rock (Dolostone, Limestone).
• They are rarely found in Precambrian Lithology while abundant in Phanerozoic time
associated with reef carbonate.
• Tectonically associated with Intra-Cratonic Settings.
• Zn and Pb are major ore minerals, with fluorite is also some time Dominated.
• They are of chemical sedimentary nature (Chemical precipitation of ore from fluids).
3/11/2018MVT DEPOSITS 4

5. HOST ROCK
• Reefal limestone is the host for MVT deposits while dolomite is also found regionally.
• The host rock lithology has three important features
1. Relative importance of Dolomite
2. The presence of erosional surfaces
3. The significance of lateral facies change
3/11/2018MVT DEPOSITS 5

6. SOURCE ROCK
• Shale plus other sedimentary rock containing Pb-Zn-F as traces are deep buried in Intra
Cratonic setting that produces over pressured Situation. Hot pore fluid escape from shale
Basin and move up aquifers to form deposits in cooler Strata, filling fractures or forming
other type of Ore bodies Sangster (1993).
• Other hypothesis indicated Gravity driven fluids flowing from a hydraulic head in a
highland are flush through a basin drinking out and replenishing the formation waters
3/11/2018MVT DEPOSITS 6

7. SUB TYPES
• MVT deposits are classified into sub types on the basis of primary ore association
• Zinc Dominant
• Lead Dominant
• Fluorite Dominant
Mineral Association: +Sphalerite ±Galena
±Ag ±Ni ±Co ± Cu (chalcopyrite)
Mineral Association: +Galina ±Sphalerite
±Ag ±Ga ±Gr ±In [±Ni ±Co] by-products
Mineral Association: +CaF2 ±Galina [±Gr
±Cadmium] by-products-> ±Sphalerite
3/11/2018MVT DEPOSITS 7
Metcalfe et al (1994)

8. ORIGIN FACTOR
• Porosity of Host Rock
• Sufficient quantity of trace element in migrating Fluid
• Release of Solution Depend on;
1. Compaction
2. Aquifer puncture
3. Faulting and Slopping
3/11/2018MVT DEPOSITS 8

9. OCCURRENCE IN PAKISTAN
• Anderson et.al, (1990) Reported MVT in Jurassic carbonates of Pakistan
• Jankovic (1986) reported at Gunga, Khuzdar district, Baluchistan
• Jones (1995) reported The Duddar Ge-Zn-Pb-Ba deposit, Balochistan
3/11/2018MVT DEPOSITS 9

10. 3/11/2018MVT DEPOSITS 10