西藏甲玛超大型铜矿区斑岩脉成岩时代及其与成矿的关系  

Zircon SHRIMP U-Pb dating of porphyry vein from the Jiama copper polymetallic deposit in Tibet and its significance

作　　者：应立娟[1] 唐菊兴[1] 王登红[1] 郑文宝[2] 秦志鹏[2] 张丽[3] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]成都理工大学地球科学学院,成都610059 [3]成都地质矿产研究所,成都610081

出　　处：《岩石学报》2011年第7期2095-2102,共8页Acta Petrologica Sinica

基　　金：国家973项目(2011CB403103);中央公益性行业科研专项课题(200911007-02);中央级公益性科研院所基本科研业务费专项资金(K0911);国土资源地质大调查项目(1212010733803;1212011112037);国家科技支撑项目(2006BAB01A01);青藏专项(1212010818089)联合资助

摘　　要：甲玛铜多金属矿是冈底斯成矿带上资源储量达到超大型规模的又一个重要矿床,2010年7月已正式投产。产于矽卡岩、斑岩和角岩中的辉钼矿Re-Os定年已表明甲玛矿床的铜钼成矿时代集中于17-14Ma,而成岩时代的研究相对较少,尤其是矿区及外围大量出露的近南北向展布的斑岩脉。本文选取矿区铅山上52号平硐内的2件弱矿化斑岩脉样品,花岗斑岩（JM52-0）和花岗闪长斑岩（JM52-46·7）,首次开展斑岩脉的锆石SHRIMPU-Pb定年,获得的206Pb/238U-207Pb/235U协和年龄分别为14·2±0·2Ma和14·1±0·3Ma,代表了甲玛矿区地表出露的近南北向展布的斑岩脉侵位时岩浆锆石的结晶年龄。斑岩脉的成岩时代与区域上与近南北向正断层系统及裂谷裂陷带有关的冈底斯含矿斑岩侵位时代（18-12Ma）一致。甲玛的成岩成矿时代显示了成岩作用与成矿作用基本同期,且与冈底斯成矿带东段主要斑岩型-矽卡岩型铜多金属矿床的成岩成矿时代基本一致,成矿高峰集中在17-14Ma之间,指示了冈底斯在中新世的岩浆构造活动事件,而且表明了甲玛铜钼矿化与岩浆热液的成因联系。The Jiama copper polymetallic deposit is an important ore deposit with a super-large scale in the Gangdese metallogenic belt of Tibet. Re-Os dating of molybdenites occurred in skarn, porphyry and hornfels has indicated the metallogenic period of Cu-Mo mineralization during 17Ma to 14Ma, whereas the research on its age of diagenesis is rather lack, especially for the porphyry veins as south-north distributed outcrops. In this paper, two samples of slightly mineralized porphyry rocks： granite porphyry （sample JM52-0） and granitic diorite porphyry （sample JM52-46.7）, have been collected from the No. 52 adit in Qianshan of the mining area. Through zircon SHRIMP U-Pb dating at the first time, their 206Pb/238U -207Pb/235U concord ages are 14.2±0.2Ma and 14.1±0.3Ma, respectively. The ages from the zircon SHRIMP U-Pb dating in this paper mean the crystallization age of magmatic zircon representing the south-north distributed granite and granitic diorite porphyry outcrops. The diagenesis age of this type porphyry veins is at the same period of ore-bearing porphyry intrusive event related to the south-north normal fault system and rift zone in Gangdese（18-12Ma）. Diagenesis and mineralization age of the Jiama copper polymetallic deposit shows the similar period for metallogenesis and diagenesis, which is similar to other porphyry-skarn type ore deposits in the east part of the Gangdese metallogenic belt with a strong concentration of mineralization during 17-14Ma, indicating the magmatic-tectonic events in Miocene in the Gangdese and the genesis relationship between Cu-Mo mineralization and hydrothermal process in Jiama.

关 键 词：锆石SHRIMP年龄 斑岩脉 成岩成矿时代 甲玛 西藏 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学]