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Multiple sulfur sources for the volcanic hosted massive sulfides in Betul Belt, Central India: Evidence from the sulfide ore chemistry and sulfur isotope geochemistry
Geochemistry ( IF 2.6 ) Pub Date : 2020-05-12 , DOI: 10.1016/j.chemer.2020.125632
Mohammad Atif Raza , Mohamed Shareef , Venkata Sri Surya Apla Naidu Badireddi , Hemraj Suryavanshi , Srinivasa Rao Baswani , Muduru Lachhana Dora , Tushar Meshram , Parwez Akhter , Raghuram , Shraddha Kumari , Biswabara Panda , Sushanta Kumar Saha , Lalit Mohan Singh Maura , Subhra Suchi Sarkar , Manish M John , Smitha Ramachandran Sarala Bai

This work provides an overview of the geological, petrological, and geochemical data available on the three volcanic-hosted massive sulfides (VHMS) deposits (Ghisi, Biskhan, and Jangaldehri) in Betul Belt, Central Indian Tectonic Zone. Sulfur isotope geochemistry was used for the first time from the Betul Belt to constrain the source of sulfur for a better understanding of the ore genesis process. Mineralization is hosted in a felsic dominant bimodal volcano-sedimentary sequence associated with syn-genetic hydrothermal alteration, i.e., intense Mg–Ca alteration (actinolite-tremolite-anthophyllite) and Al–Fe alteration zone (gahnite-garnet-biotite-staurolite) followed by regional metamorphism. Field observations, drill core logging, and petrography studies reveal different modes of mineralization, i.e., dissemination, stringers, and semi-massive sulfides vein, comprises of chalcopyrite, sphalerite, pyrite, galena with lesser pyrrhotite, are paragenetically distinct in three deposits. The petrography, SEM-EPMA studies show the presence of chalcopyrite disease in Fe-rich sphalerite at Biskhan and Jangaldehri in the east and absence of the same texture at Ghisi in the west. This difference reveals the variable physio-chemical nature of the hydrothermal fluid and partial melting of sulfides during subsequent metamorphism.

Cu–Fe mineralization was deposited from high-temperature hydrothermal fluids with less sulfur activity at Biskhan-Jangaldehri. Later Zn–Cu–Pb mineralization was formed from lower temperature hydrothermal fluids with higher sulfur activity. The δ34S values of sulfides (sphalerite, chalcopyrite, and pyrite) from three deposits show a wide range of sulfur values (δ34S) from −12.87 to + 19.31‰ (n = 27), consistent with heterogeneous sourcing of S, probably combining magmatic source along with the reduction of seawater sulfate. Variation in the sulfur isotopic compositions of sulfide was the result of dilution and cooling of the metalliferous fluid at different stages after interaction with meteoric, seawater and hydrothermal fluids, which caused the deposition of base metal sulfides.

Sulfides from Ghisi in the west display both +ve and −ve values (−12.88 to + 0.38‰; n = 10), suggest sulfur predominantly derived by thermochemical reduction of seawater sulfate with minor input of magmatic sulfur reduction lead to polymetallic Zn–Cu–Pb mineralization. The gradual increasing in the δ34S values (more + ve values +18.65 to +19.31‰; n = 8) from west to east at Biskhan and Jangaldehri (+ 5.01 to + 8.3‰, n = 9) may be due to involvement of both the leaching of igneous basement rocks and chemical process of seawater sulfates by thermochemical reduction (TSR) from deep water levels lead to Zn–Cu mineralization. This δ 34S variation occurs in three deposits of the Betul Belt due to modifications of the primary mineralization during subsequent stages of ore formation and metamorphism, indicating a complex fluid evolution history for VHMS deposits in Betul Belt, Central India, where S derived from a heterogeneous source by multiple geological processes. This situation is more akin to many established VHMS deposits of ancient and modern submarine hydrothermal systems.



中文翻译:

印度中部伯特带火山中大量块状硫化物的多种硫源:来自硫化物矿石化学和硫同位素地球化学的证据

这项工作概述了中部印度洋构造带贝图尔带的三个火山岩块状硫化物(VHMS)矿床(Ghisi,Biskhan和Janggaldehri)可获得的地质,岩石和地球化学数据。必拓(Betul)带首次使用了硫同位素地球化学来限制硫的来源,以便更好地了解矿石的成因过程。矿化作用存在于与同生型热液蚀变有关的长英质优势双峰火山沉积沉积序列中,即强烈的Mg-Ca蚀变(阳起石-透闪石-角闪石)和Al-Fe蚀变带(钠铁矿-石榴石-黑云母-星形石)通过区域变质。现场观察,钻芯测井和岩石学研究揭示了不同的成矿模式,即散布,纵梁,半块状硫化物脉,由黄铜矿,闪锌矿,黄铁矿,方铅矿和较少的黄铁矿组成,在三个矿床中具有方铅矿学区别。岩石学,SEM-EPMA研究表明,东部的Biskhan和Jangaldehri的富铁闪锌矿中存在黄铜矿病,而西部的Ghisi则没有相同的质地。这种差异揭示了热液的可变的物理化学性质以及在随后的变质过程中硫化物的部分熔化。

在Biskhan-Jangaldehri,Cu-Fe矿化作用是由硫活性较低的高温热液形成的。后来的Zn-Cu-Pb矿化是由具有较高硫活度的低温热液形成的。的δ 34期从三个矿床广泛硫值的硫化物的值(闪锌矿,黄铜矿,黄铁矿和)示出了(δ 34S)从-12.87到+ 19.31‰(n = 27),这与S的异质来源一致,可能是岩浆源与海水硫酸盐的还原相结合。硫化物的硫同位素组成的变化是在与大气,海水和热液相互作用后,在不同阶段对含金属流体进行稀释和冷却的结果,这导致了贱金属硫化物的沉积。

西部吉西(Ghisi)的硫化物同时显示+ ve和-ve值(−12.88至+ 0.38‰; n = 10),表明硫主要来自对海水硫酸盐进行热化学还原而得到的岩浆硫减少量少,从而导致多金属Zn-Cu –铅矿化。在逐渐增加的δ 34价值观(更+已经值18.65到19.31 +‰; N = 8)从西在Biskhan和Jangaldehri向东(+ 5.01到8.3 +‰,N = 9),可能是由于参与深水位热化学还原(TSR)引起的火成岩基岩的浸出和海水硫酸盐的化学过程都导致锌铜矿化。这δ 34在矿石形成和变质的后续阶段,由于初级矿化作用的改变,在Betul带的三个矿床中发生了S变化,这表明印度中部Betul带的VHMS矿床有复杂的流体演化历史,其中S来源于不同来源。多个地质过程。这种情况更类似于古代和现代海底热液系统的许多已建立的VHMS矿床。

更新日期:2020-05-12
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