云南墨江金厂镍-金矿床镍矿化地质特征及形成时间  

Geology and formation time of nickel mineralization in Jinchang nickel-gold deposit, Mojiang, Yunnan

作　　者：应汉龙[1] 王登红[2] 刘和林[3] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国地质科学院矿产资源研究所,北京100037 [3]云南省地质矿产勘查开发局第二地质大队,云南文山653000

出　　处：《矿床地质》2005年第1期44-51,共8页Mineral Deposits

基　　金：国家重点基础研究项目(编号:G1999043203)的资助

摘　　要：云南墨江金厂镍_金矿床位于北西走向的哀牢山蛇绿混杂岩带,镍矿体分布于金厂超基性岩体接触带附近的北西走向构造破碎带中,含矿围岩主要为上泥盆统金厂组烂山段变余粉砂岩、石英岩和板岩,少数为硅质菱镁岩和蛇纹岩。镍矿体与围岩为过渡关系,多数与金矿体在空间上分离,少数重叠、穿插,镍矿化时间晚于金矿化。镍矿体以强烈铬绢云母化、硅化和黄铁矿化为特征,矿石类型有绿色泥岩稠密浸染状黄铁矿型和石英岩浸染状黄铁矿型两种,含镍0.5%至1.2%。矿石的金属矿物组合为黄铁矿_方硫镍矿_辉砷镍矿_辉锑矿_闪锌矿,镍矿化属于中低温热液矿化。为了了解金厂镍矿化与超基性岩成岩的时间和成因联系,在了解区域超基性岩体形成时代的基础上,测定了两类镍矿体中3个蚀变铬绢云母的40Ar/39Ar年龄。铬绢云母的40Ar/39Ar似坪年龄分别为(63.09±0.16)Ma、(62.05±0.14)Ma和(61.55±0.23)Ma,代表镍矿化时间。镍矿化发生于新生代初,比金厂超基性岩侵入晚240Ma以上,金厂镍_金矿床镍矿体是海西期形成的金厂超基性岩在新生代初受热液淋滤形成的。The Jinchang nickel_gold deposit is located in the NW_trending Ailaoshan ophiolitic mélange. The nickel orebodies are controlled by the NW_striking fault and fracture zones near the contact zone of the Jinchang ultrabasic intrusion and hosted mainly by blastosiltstone, quartzite and slate of the Lanshan Member of Upper Devonian Jinchang Formation and casually by siliceous pinolite and serpentinite. Grading into country rocks, the nickel orebodies are mostly separated from and subordinately superimposed on or intersecting gold orebodies, suggesting that they are younger than the gold orebodies. Intense 'green mica' (Cr_sericite) alteration, silicification and pyritization are closely associated with the nickel ores. Two types of nickel ores are recognized, namely densely pyrite disseminated green mudstone type and pyrite disseminated quartzite type, which contain 0.5%～1.2% nickel. Pyrite_vaesite_gersdorffite_stibnite_sphalerite makes up the metallic mineral assemblage of the nickel ore. The nickel mineralization was formed at medium_low temperature. ~ ~40 Ar/~39 Ar plateau_like ages of three nickel mineralization_related chromium sericite samples from two different types of nickel orebodies are (63.09±0.16) Ma, (62.05±0.14) Ma and (61.55±0.23) Ma respectively, which are identical with the time of nickel mineralization. The nickel orebodies were formed at the beginning of Cenozoic and are over 240 Ma younger than the Jinchang ultrabasic intrusion. The late hydrothermal fluids leached the Jinchang ultramafic intrusion and led to the formation of the nickel orebodies in the Jinchang nickel_gold deposit.

关 键 词：地球化学 镍矿化 成矿时代 ^40Ar/^39Ar定年 铬绢云母 金厂镍-金矿床 云南 

分 类 号：P618.63[天文地球—矿床学] P618.51[天文地球—地质学]