Distal axis sulfide mineralization on the ultraslow-spreading Southwest Indian Ridge:an LA-ICP-MS study of pyrite from the East Longjing-2 hydrothermal field  

作　　者：Shili Liao Chuanwei Zhu Jianping Zhou Weiyong Liu Junyu Yu Jin Liang Weifang Yang Wei Li Jia Liu Chunhui Tao 

机构地区：[1]Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China [2]Key Laboratory of Submarine Geosciences,Ministry of Natural Resources,Hangzhou 310012,China [3]State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China [4]Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province,School of Earth Sciences,Zhejiang University,Hangzhou 310027,China

出　　处：《Acta Oceanologica Sinica》2021年第5期105-113,共9页海洋学报（英文版）

基　　金：The National Key Research and Development Program of China under contract Nos 2016YFC1401210,2018YFC0309902 and 2017YFC0306603;Zhejiang Provincial Natural Science Foundation of China under contract No.LQ19D060002;the National Natural Science Foundation of China under contract No.42006074;China Ocean Mineral Resources R&D Association Project under contract No.DY135-S1-1-02。

摘　　要：The newly discovered East Longjing-2 hydrothermal field(ELHF-2)is located on the Dragon Horn oceanic core complex of the ultraslow-spreading Southwest Indian Ridge,approximately 12 km from the ridge axis.This study measured the chemical compositions of pyrite from ELHF-2 using a laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)to investigate the genesis of the field.Three generations of pyrite were classified,and found that:Py1 and Py2,rich in V,Mn,U,and Se,occur in altered basalt debris and the silica alteration matrix,respectively.Py3 was mainly intergrown with chalcopyrite in quartz veins and had higher Cu,In,Ag,Sb,and Au contents than Py1 and Py2.Some elements,such as Au,Se,and Pb,are likely presented as direct substitution with Fe^(2+)in pyrite,while Cu,Zn,Co,Ni,and Ag probably occur both as direct substitution with Fe and as distributed micro-to nanoparticle-sized sulfides.Meanwhile,the occurrence of V,Mn,and U is likely presented as oxide inclusions.Trace element geochemistry suggested that the pyrite was formed under hightemperature conditions,and the ore forming elements were likely derived from ultramafic rocks.In addition,Py1and Py2 were formed under higher water/rock ratio and higher temperature conditions,with more seawater involvement compared with Py3.The formation of ELHF-2 was probably driven by exothermic serpentinization reactions with an additional magmatic heat.This study shows that high-temperature hydrothermal circulation driven by magmatic activity can be developed on distal rift flank areas of magma-starved ultraslow-spreading ridges.

关 键 词：pyrite geochemistry LA-ICP-MS hydrothermal activity Southwest Indian Ridge 

分 类 号：P736[天文地球—海洋地质]