Mississippi valley type deposits

Muhammad Bilal
Department of geology
university of Peshawar

1. Muhammad Bilal (23) Mississippi valley type deposits 3/11/2018 MVT Deposits 1

2. content Introduction Host rock Source rock (fluid flow) 3 sub types Origin factors Occurrence in Pakistan 3/11/2018 MVT 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). 3/11/2018 MVT 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). 3/11/2018 MVT 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 Relative importance of Dolomite The presence of erosional surfaces The significance of lateral facies change Occurrence of Dolomite regionally with the limestone body is necessary as Dolomite is one of alteration product Prominent erosional surface which represent extensive Karshification, characterizes all the major MVT deposits. Sangster (1993) concluded that in most cases there is no marked lateral facies change in the ore-hosting sedimentary units. 3/11/2018 MVT 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 3/11/2018 MVT 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: +CaF 2 ±Galina [±Gr ±Cadmium] by-products-> ±Sphalerite 3/11/2018 MVT 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; Compaction Aquifer puncture Faulting and Slopping 3/11/2018 MVT 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 3/11/2018 MVT Deposits 9

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