西南印度洋脊龙旂热液场金属硫化物的矿物学组成及指示意义  

Mineralogical composition and its significance of hydrothermal sulfides from the Longqi hydrothermal field on the Southwest Indian Ridge

作　　者：曹红 孙治雷[1,2] 刘昌岭 姜学钧[1,2] 黄威 徐翠玲[1,2] 刘莉萍 何拥军[1,2] CAO Hong;SUN Zhilei;LIU Changling;JIANG Xuejun;HUANG Wei;XU Cuiling;LIU Liping;HE Yongjun(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;China Key Laboratory of Submarine Geosciences and Technology,Ministry of Eclueation,Department of Marine Geoscience,Ocean Univer-sity of China,Qingdao 266010,China)

机构地区：[1]自然资源部天然气水合物重点实验室,青岛海洋地质研究所,青岛266071 [2]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,青岛266071 [3]海洋科学与技术重点实验室,中国海洋大学海洋地球科学学院,青岛266010

出　　处：《海洋地质与第四纪地质》2018年第4期179-192,共14页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金“西南印度洋龙旂热液区硫化物风化蚀变中元素的迁移和富集”(41606086); 泰山学者专项(ts201712079); 中国地质调查局国家专项(DD20160218,DD20160344)

摘　　要：西南印度洋脊(SWIR)是当前洋底超慢速扩张洋脊的典型代表,具有独特的热液硫化物矿床形成机理,对位于该洋脊的龙旂热液场硫化物样品进行了系统的矿物学分析,结果表明:该区硫化物为高温热液喷溢活动所形成的富Fe型硫化物,目前已经历了一定程度的氧化蚀变;硫化物矿物组合以磁黄铁矿、黄铁矿为主,其次是少量黄铜矿、白铁矿和(铁)闪锌矿;黄铜矿出溶等轴古巴矿现象普遍,部分样品中可见自然金颗粒。经综合分析,该区热液成矿作用可划分为3个成矿阶段和1个后期海底风化阶段:(1)高温的黄铁矿+黄铜矿(等轴古巴矿)+磁黄铁矿阶段,(2)中高温的黄铁矿+闪锌矿阶段,(3)低温的胶状或莓球状黄铁矿+白铁矿+自然金阶段,(4)后期硫化物海底氧化性蚀变阶段主要是形成Fe的氧/羟化物。在整个成矿期间,流体温度有不同程度的波动,主要硫化物矿物形成时端元流体的温度应在335℃以上,瞬间(短时)或局部热液的最高温度推测超过400℃。本区的磁黄铁矿属于富钴型磁黄铁矿亚类,经历了六方磁黄铁矿+黄铁矿→单斜磁黄铁矿+黄铁矿的变化,表明该区热液流体发生了快速降温的演化过程。As a typical ultraslow-spreading oceanic ridge with huge amount of hydrothermal sulfide deposits,the Southwest Indian Ridge is known for its unique mineralizaiton environment.In this paper,we presented hereby the detailed mineralogy of the hydrothermal metal sulfides recovered from the Longqi hydrothermal field of the Ridge.Our results suggested that the mineral assemblage of the deposits is highly weathered and dominated by pyrrhotite and pyrite,along with a little of sphalerite（Fe）and chalcopyrite（isocubanite）.In addition,minor natural gold grains are sometimes observed.There are three metallogenic stages in addition to the latest seafloor weathering（1）the high temperature stage characterized by pyrite,pyrrhotite and chalcopyrite（isocubanite）;（2）the medium temperature stage marked by the mineral assemblage of pyrite and sphalerite;（3）the low-temperature stage characterized by the mineral assemblage of colloform pyrite.The seafloor weathering is characterized by Fe-oxyhydroxide.The precipitation of the main sulfide minerals is presumed to be at a temperature above 335 ℃ and experienced episodic instantaneous temperature as high as 400 ℃.The Co-rich pyrrhotite in this metal sulfide deposits has changed from monoclinic pyrrhotite＋ pyrite to hexagonal pyrrhotite＋ pyrite,indicating a rapid coolingprocess of the hydrothermal fluid during the mineralization.

关 键 词：热液硫化物 矿物学 成矿序列 指示意义 龙旂热液场 

分 类 号：P736.3[天文地球—海洋地质]