Submarine Exhalative Deposits.pptx

INTRODUCTION
CLASSIFICATION OF SUBMARINE EXHALATION VOLCANIC MASSIVE SULPHIDE DEPOSITS(VMS DEPOSIT)
SEDIMENTARY EXHALATIVE DEPOSITS(SEDEX DEPOSIT) CONCLUSION
REFERRENCE

1. SUBMARINE VOLCANIC EXHALATION SUBMITTED BY- JYOTIRMAYEE MAHANTA M.Sc. 1 st year(2 nd semester) 22GEOL019

2. CONTENTS INTRODUCTION CLASSIFICATION OF SUBMARINE EXHALATION VOLCANIC MASSIVE SULPHIDE DEPOSITS(VMS DEPOSIT) SEDIMENTARY EXHALATIVE DEPOSITS(SEDEX DEPOSIT) CONCLUSION REFERRENCE

3. INTRODUCTION This process involves exhalation of hydrothermal fluids at the surface, usually under submarine conditions and generally producing stratiform ore bodies. Deposits resulted from this process is known as VMS deposit. Volcanic associated massive sulphide deposit frequently show a close spatial relationship to volcanic rocks but this is not the case all the deposits, Example- Sullivan, Canada which is sediment hosted and are referred to as SEDEX deposit.

4. https://images.app.goo.gl/BGb3E4FBcNv2243r8

5. CLASSIFICATION OF SUBMARINE EXHALATIVES

6. VOLCANOGENIC MASSIVE SULFIDE(VMS)DEPOSIT These are exhalations of sulphide rich magma at the surface, usually under marine conditions. The deposits formed from this process can be known as volcanic exhalative deposit. The ores show relationship to volcanic rock. VMS deposits are the source of pyrite with varying amount of copper, lead, zinc and barite . VMS deposits are epigenetic. Stratiform or stratabound nature of ore deposit. Minor amount of gold and silver are also found. VMS deposits are generally associated with black smokers.

7. Types of smokers or hydrothermal vents BLACK SMOKER- Iron sulphide (black)

8. Continued… WHITE SMOKER- Barite, Calcite(White)

9. MORPHOLOGY OF VMS DEPOSITS VMS deposits have a wide variety of morphologies, with mound shaped and bowl shaped deposits most typical. The bowl-shaped formations formed due to venting of hydrothermal solutions into submarine depressions. VMS deposits have an ideal form of a conical area of highly altered volcanic or volcanogenic sedimentary rock within the feeder zone, which is called the  stringer sulfide  or  stockwork  zone, overlain by a mound of massive exhalites , and flanked by stratiform exhalative sulfides known as the  apron . Stockwork Zone- Vein hosted sulfides(chalcopyrite, pyrite, pyrrhotite) with quartz, chlorite and lesser barite and calcite. Mound Zone- laminated massive to  brecciated  pyrite,  sphalerite  (+/- galena) ,  hematite , and barite . Apron Zone-  generally more  oxidised , manganese , barium and hematite enriched, with  cherts ,  jaspers.  

10. A cross-section of a typical volcanogenic massive sulfide (VMS) ore deposit as seen in the sedimentary record

11. Metal Zonation Most VMS deposits show metal zonation, caused by the changing physical and chemical environments of the circulating hydrothermal fluid. Ideally, this forms a core of massive  pyrite  and  chalcopyrite  around the throat of the vent system, with a halo of chalcopyrite- sphalerite -pyrite grading into a distal sphalerite- galena  and galena- manganese  and finally a  chert -manganese- hematite  facies. Most VMS deposits show a vertical zonation of  gold , with the cooler upper portions generally more enriched in gold and silver. The  mineralogy  of VMS massive sulfide consists of over 90% iron sulfide, mainly in the form of  pyrite , with  chalcopyrite ,  sphalerite  and  galena  also being major constituents.

12. Types of VMS deposit A)On the basis of sulphide content and ore deposits and its relation to the volcanic stratigraphy, it is of two types. 1) Massive type- sulphide mineral>60%, stratiform and stratabound. 2) Stringer or vein type – sulphide mineral<20%, crosscut stratigraphy.

13. Continued ... B)On the basis of host rock, metal content and alteration assemblage there are six types. Mafic(Cyprus type) Bimodal Mafic(Noranda type) Mafic Siliciclastic( Besshi type)(aka Pelitic Mafic) Bimodal Felsic(Kuroko type) Felsic Siliciclastic(Bathurst type) Hybrid Bimodal Felsic/Siliciclastic( Eskay Creek type)

14. Continued… Mafic(Mafic- Backarc ) Ophiolite- hosted. Forearc or backarc . Basalts and sheeted dyke hosted. Cu-(Zn-Au) rich. Global Examples Cyprus Oman NL Ophiolites

15. Continued... Bimodal Mafic Mafic-dominated settings Deposits often hosted by felsic rocks. Cu-Zn-(Au) rich. Global Examples Noranda Flin Flon Rambler-Ming

16. Continued… Mafic Siliciclastic Mafic rocks and sediments Mafic or ultramafic intrusions. Cu-(Zn, Co, Au)rich . Global Examples Besshi (Japan), Windy Craggy(British Columbia)

17. Continued… Bimodal Felsic Felsic dominated settings. Flow dominated environments. Bimodal. Zn-Pb-Cu rich. Global Examples Kuroko, Hellyer Buchans

18. Continued… Felsic Siliciclastic Sediment rich. Felsic volcaniclastic rocks. Abundant felsic and mafic sills. Graphitic shales+/- iron formations/exhalations Tabular deposits. Zn-Pb-(Ag, Au) rich. Global Examples Bathurst, IPB

19. Continued… Hybrid Bimodal Felsic Felsic & mafic rocks with sediments. Characteristics of epithermal and VMS. Aluminous alteration occurs. Zn-Pb rich(VMS). Hg-Bi-Sb-As-Au-Ag-S rich. Global Examples Eskay Creek Rambler

20. SEDEX DEPOSITS Sedimentary exhalatives (SEDEX). These deposits are formed by release of ore bearing hydrothermal fluids into the ocean resulting in the precipitation of stratiform ore. Laminated sulfide deposits of Pb-Zn. Lacks in volcanic components and absence of hydrothermal alteration. Also known as bimetallic deposits. Hosted largely by clastic rocks deposited in intra-continental rifts or failed rift basins and passive continental margins. Important source of Pb, Zn and major contributor o f Ag, Cu, Au, Bs, W.

21. Banded ore with Chalcopyrite, Galena, Sphalerite, Pyrite, from the SEDEX Rammelsberg deposit, Germany Main economic minerals are sphalerite( Zns ) & galena(Pbs). Indian Example Mochia -Rajpura- Dariba

22. CARBONATE HOSTED DEPOSITS Two types- Irish type & Mississippi valley type Irish Type Pb- Zn deposits, strata bound sphalerite galena and iron sulfide accompanied by dolomite, calcite and barite as gangue hosted in carbonate sedimentary rocks. Mississippi Valley Type(MVT) Epigenetic deposits. Strata bound in nature. Carbonate hosted ore bodies. Originate from saline bearing metalliferous fluids.

23. CONCLUSION Both the SEDEX & VMS deposits are products of submarine hot springs. VMS deposits are dominantly copper and zinc. SEDEX deposits are dominantly zinc and lead but generally less common than VMS deposits. In VMS deposits the metals are usually zoned with copper near the vent and then zinc and lead more distant to that. These deposit types are major global sources of base metals particularly zinc.

24. REFERRENCES Volcanogenic Massive sulfide deposits : ALAN G. GALLEY, D.HANNINGTON AND IAN R. JONASSON https://www.scribd.com/presentation/282329080/6-SEDEX-VMS-MVT https://www.911metallurgist.com/blog/difference-between-sedex-vs-vms-deposits https://en.wikipedia.org/wiki/Volcanogenic_massive_sulfide_ore_deposit

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