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现代海底热液硫化物的成矿序列和指示意义——以印度洋中脊为例
曹红,孙治雷,刘昌岭,姜子可,徐翠玲,黄威,李东义
0
(青岛海洋地质研究所、自然资源部天然气水合物重点实验室,山东 青岛 266071;青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室,山东 青岛 266071;山东省科学院海洋仪器仪表研究所,山东 青岛 266001;国家海洋局第三海洋研究所,福建 厦门 361005)
摘要:
与快速扩张的洋中脊相比,主要由超慢速-慢速扩张洋脊组成的印度洋中脊具有独特的热液硫化物成矿模式.运用高精度矿相显微镜、XRD、电子探针和ICP-AES/MS等测试手段,对印度洋中脊的热液硫化物矿床样品开展了矿物成分、结构构造、地球化学等各方面分析.结果表明,来自中印度洋脊(CIR)艾德蒙德(Edmond)热液区的硫化物A主要由黄铁矿、白铁矿以及黄铜矿构成,其成矿期次可划分为白铁矿-黄铁矿阶段(Ⅰ)、闪锌矿-黄铜矿阶段(Ⅱ)以及后期石英阶段(Ⅲ),成矿流体温度经历了低-高-低的变化;同样来自于艾德蒙德热液区的硫化物B主要矿物成分为黄铁矿、白铁矿和硬石膏,成矿期次划分为硬石膏-白铁矿-黄铁矿阶段(Ⅰ)和胶状黄铁矿-石英(Ⅱ)2个阶段,流体温度经历了低-高的变化;与之相比,来自西南印度洋脊(SWIR)龙旂热液区的硫化物C主要由纤铁矿、黄铜矿、黄铁矿和白铁矿组成,成矿期次划分为纤铁矿-白铁矿-黄铁矿阶段(Ⅰ)和闪锌矿黄铜矿(Ⅱ)阶段,后期闪锌矿、黄铜矿的出现反映热液流体温度发生了升高.地球化学特征表明,印度洋中脊的热液硫化物总体为富Fe型,并相对富集Co和Ni元素,而Zn和Cu元素的含量相对较低.此外,取自艾德蒙德热液区的硫化物与EPR 21°N热液硫化物组成非常相似,而与慢速扩张脊TAG相比,Pb、Zn、Ag和Sr元素含量较高,Cu和Fe元素含量则较低.
关键词:  海洋地质学  矿物组成  成矿序列  指示意义  热液硫化物  印度洋中脊
DOI:
基金项目:国家自然科学基金资助项目(41606086);泰山学者专项资助项目(ts201712079);国家海洋局重点实验室开放基金资助项目(HY201809);中国地质调查局国家专项资助项目(DD20160218,DD20160344);山东省科技重大专项资助项目(2015ZDZX08001)
Metallogenic sequence and significance of modern seafloor hydrothermal sulfide with an example from Indian Ocean Ridge
CAO Hong,SUN Zhi-lei,LIU Chang-ling,JIANG Zi-ke,XU Cui-ling,HUANG Wei,LI Dong-yi
(The Key Laboratory of Gas Hydrate,Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;Institute of Oceanographic Instrumentation, Shandong Academy of Sciences, Qingdao 266001, China;Third Institute of Oceanography, SOA, Xiamen 361005, China)
Abstract:
Comparing with the fast spreading ridge, the hydrothermal sulfides, collected from the ultra-slow and slow Indian Ocean Ridge, would be expected to exhibit a unique mineralization model. Here, the mineral compositions, textural and geochemical features of hydrothermal sulfide ores were reported by using ore microscope, X-ray diffraction, Electron microprobe and ICP-AES/MS analysis techniques. Based on the mineralogical investigations, the sample AIR1 collected from Central Indian Ridge (CIR) Edmond hydrothermal field mainly consists of pyrite, marcasite and chalcopyrite and can be divided into early marcasite-pyrite stage (I), sphalerite-chalcopyrite stage (II) and later covellite-digenite stage (III), the hydrothermal fluid temperature experienced a low-high-low period. The sample AIR2 from Edmond field is predominantly composed of pyrite, marcasite and gypsum. The metallogenic period can be divided into early gypsum-marcasite-pyrite stage (I) and later colloidal pyrite-quartz stage (II). The fluid temperature experienced a shift from low to high period. The sample ISU1 from Southwest Indian Ridge (SWIR) Longqi hydrothermal field mainly consists of lepidocrocite, chalcopyrite, pyrite and marcasite. At the same time it can be identied to early lepidocrocite-marcasite-pyrite stage (I) and later sphalerite-chalcopyrite stage (II). The occurrence of sphalerite and chalcopyrite in the sample ISU1 reflects the rise of the later hydrothermal fluid temperature. The integrative geochemical analysis shows that the hydrothermal sulfides are relatively enriched in Fe, Co and Ni with comparatively low amounts of Zn and Cu. Furthermore, the sulfides recovered from Edmond field show the most similarity to that of hydrothermal sulfides from the site of EPR 21°N. In contrast with the sulfides from the slow spreading TAG hydrothermal system, the sulfides in the Indian Ocean Ridge character significantly higher Pb、Zn、Ag and Sr contents, and lower Cu and Fe contents.
Key words:  marine geology  mineral composition  metallogenic sequence  geological significance  hydrothermal sulfide  Indian Ocean Ridge

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