Mineralogical characteristics of polymetallic sulfides from the Deyin-1 hydrothermal field near 15°S, southern Mid-Atlantic Ridge

• Published in: Acta oceanologica Sinica Vol. 36; no. 2; pp. 22 - 34
• Main Authors: Wang, Shujie, Li, Huaiming, Zhai, Shikui, Yu, Zenghui, Shao, Zongze, Cai, Zongwei
• Format: Journal Article
• Language: English
• Published: Beijing The Chinese Society of Oceanography 01.02.2017; Springer Nature B.V; Key Laboratory of Submarine Geosciences and Prospecting Techniques of Ministry of Education, College of Marine Geosciences, 0cean University of China, Qingdao 266100, China%Key Laboratory of Submarine Geosciences, Second Institute of 0ceanography, State 0ceanic Administration, Hangzhou 310012, China%Key Laboratory of Marine Biogenetic Resources, Third Institute of 0ceanography, State 0ceanic Administration, Xiamen 361005, China
• Subjects: Chalcopyrite; Chemical composition; Climatology; Copper; Cruises; Crystallization; Crystals; Earth and Environmental Science; Earth Sciences; Ecology; Electron microprobe; Electron probes; Engineering Fluid Dynamics; Environmental Chemistry; Galena; Heavy metals; High temperature; Hydrothermal fields; Inclusions; Iron; Low temperature; Marine & Freshwater Sciences; Mid-ocean ridges; Mineral resources; Mineralization; Mineralogy; Minerals; Ocean floor; Oceanography; Optical microscopes; Pyrite; R&D; Research & development; Scanning electron microscopy; Sequencing; Sphalerite; Sulfides; Sulphides; Zinc; Zincblende; 多金属硫化物; 大洋矿产资源; 大西洋中脊; 扫描电子显微镜; 热场; 矿物学特征; 磁黄铁矿; 铁闪锌矿; Mid-Atlantic Ridge; mineral-forming sequence; mineralogical characteristics; polymetallic sulfides; southern Mid-Atlantic Ridge; Deyin-1 hydrothermal field
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-016-0961-3

A seafloor hydrothermal field, named Deyin-1 later, near 15°S southern Mid-Atlantic Ridge（SMAR） was newly found during the 22 nd cruise carried out by the China Ocean Mineral Resources Research ＆ Development Association（COMRA）. Sulfide samples were collected at three stations from the hydrothermal field during the26 th cruise in 2012. In this paper, mineralogical characteristics of the sulfides were analyzed with optical microscope, X-ray diffractometer, scanning electron microscope and electron microprobe to study the crystallization sequence of minerals and the process of hydrothermal mineralization. According to the difference of the ore-forming metal elements, the sulfide samples can be divided into three types：（1） the Ferich sulfide, which contains mainly pyrite and chalcopyrite;（2） the Fe-Cu-rich sulfide consisting predominantly of pyrite, chalcopyrite and isocubanite, with lesser amount of sphalerite, marmatite and pyrrhotine; and（3） the Fe-Zn-rich sulfide dominated by pyrite, sphalerite and marmatite, with variable amounts of chalcopyrite, isocubanite, pyrrhotine, marcasite, galena and gratonite. Mineral precipitations in these sulfides are in the sequence of chalcopyrite（isocubanite and possible coarse pyrite）, fine pyrite,sphalerite（marmatite）, galena, gratonite and then the minerals out of the dissolution. Two morphologically distinct generations（Py-I and Py-II） of pyrite are identified in each of the samples; inclusions of marmatite tend to exist in the coarse pyrite crystals（Py-I）. Sphalerite in the Fe-Zn-rich sulfide is characterized by a＂chalcopyrite disease＂ phenomenon. Mineral paragenetic relationships and a wide range of chemical compositions suggest that the environment of hydrothermal mineralization was largely changing. By comparison, the Fe-rich sulfide was formed in a relatively stable environment with a high temperature, but the conditions for the formation of the Fe-Cu-rich sulfide were variable. The Fe-Zn-rich sulfide was precipitated during the hydrothermal venting at relatively low temperature.