新疆清水铬铁矿床铬尖晶石成分与矿床成因研究  

Genesis of Qingshui chromite deposits from Karamaili ophiolite belt in eastern Junggar,Xinjiang,China

作　　者：解洪晶[1] 王玉往[1] 郭博然 周国超 XIE Hongjing;WANG Yuwang;GUO Boran;ZHOU Guochao(Beijing Institute of Geology and Mineral Resources Co.,Ltd.,Beijing 100012;School of Earth Science and Resources,China University of Geosciences,Beijing 100083)

机构地区：[1]北京矿产地质研究院有限责任公司,北京100012 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《矿产勘查》2021年第4期858-867,共10页Mineral Exploration

基　　金：国家重点研发计划(编号:2017YFC0601204)资助。

摘　　要：蛇绿岩中产出的豆荚状铬铁矿是铬的主要来源,对其成因研究一直是地质学家关注的焦点。新疆卡拉麦里蛇绿岩带位于准噶尔盆地东北缘,产出有清水、苦水泉等铬铁矿床,对其研究可为该区未来找矿方向提供理论支撑。本文重点对清水铬铁矿床中矿石和岩体中的铬尖晶石进行矿物学、矿物化学研究,探讨矿床的母岩浆成分、成矿构造背景和成矿作用过程。研究得出,清水铬铁矿床副矿物铬尖晶石主要见于纯橄岩和单辉橄榄岩,具有较低的Cr_(2)O_(3)(30.73%~40.12%)和Cr^(#)(35~51),较高的Al_(2)O_(3)(22.03%~31.15%)含量,矿石中铬尖晶石具有比副矿物铬尖晶石更高的Cr_(2)O_(3)(53.06%~58.31%)和Cr^(#)(80~83)、更低的Al_(2)O_(3)(8.26%~9.32%)含量。经过数值模拟计算得出,母岩浆熔体含有9.56%~10.05%的Al_(2)O_(3),0.45%~0.89%的TiO_(2),0.74~1.71的FeO/MgO。在泥盆纪,卡拉麦里古洋盆的拉张使得软流圈上涌而发生减压熔融,从而熔出大洋玄武岩,形成地幔残留橄榄岩,与此同时形成副矿物铬尖晶石,从而使得铬铁矿得以初始富集。随着卡拉麦里洋盆打开、俯冲,俯冲带上盘发生高程度部分熔融和充分的熔岩反应,使早期大洋中脊(MORB)背景下形成的铬铁矿进一步聚集形成规模较大的致密块状铬铁矿。Podiform chromite in ophiolite is the main source of chromium,and its genesis has always been the focus of geologists.Karamaili ophiolite belt is located in the northeast margin of Junggar basin,Xinjiang,where Qingshui chromite deposit occurred.This paper focuses on the study of chromium spinel in Qingshui chromite deposit,and discusses the parental melt composition,tectonic setting and metallogenic process of the deposit.The results show that the accessory chromium spinel is mainly found in dunite and harzburgite with lower Cr_(2)O_(3)(30.73%~40.12%)and Cr^(#)(35~51),higher Al_(2)O_(3)(22.03%~31.15%)content,while the chromium spinel in ores shows higher Cr_(2)O_(3)(53.06%~58.31%)and Cr^(#)(80~83)and lower Al_(2)O_(3)(8.26%~9.32%)than accessory chromium spinel.The parental magma melt contains 9.56%~10.05%of Al_(2)O_(3),0.45%~0.89%of TiO_(2),0.74~1.71 of FeO/MgO.During the Devonian,decompression melting caused the upwelling of deep mantle materials,which resulted in the extrusion of oceanic basalts and the formation of mantle residual peridotite.At the same time,chromian spinels were formed,which led to the initial enrichment of chromite.With the subduction of the Karamaili ocean,the high degree of partial melting and sufficient melt rock reaction occurred in the subduction zone resulted in the further accumulation of chromite formed in the early MORB background and the formation of large-scale massive chromite.

关 键 词：蛇绿岩 铬铁矿 铬尖晶石 清水 东准噶尔 

分 类 号：P618.33[天文地球—矿床学]