东准噶尔和尔赛斑岩铜矿成岩成矿时代与形成的构造背景  

Chronology and tectonic setting of the intrusive bodies and associated porphyry copper deposit in Hersai area,eastern Junggar

作　　者：杜世俊[1,2] 屈迅[3] 邓刚[3] 张永[1] 程松林[3] 卢鸿飞[3] 吴琪[1] 徐兴旺[1] 

机构地区：[1]中国科学院矿产资源重点实验室中国科学院地质与地球物理研究所,北京100029 [2]海南省地质环境监测总站,海口571100 [3]新疆维吾尔自治区地质矿产勘查开发局,乌鲁木齐830000

出　　处：《岩石学报》2010年第10期2981-2996,共16页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-YW-107);中国科学院矿产资源重点实验室基金资助;"十一五"国家科技支撑计划重点项目(2006BAB07B01-03)

摘　　要：东准噶尔和尔赛铜矿是近年来新发现的斑岩型铜矿,位于野马泉-琼河坝古生代岛弧带东段。成矿岩体为侵位于花岗闪长岩中的花岗闪长斑岩,花岗闪岩中包含有钾长花岗岩体。锆石CAMECA U-Pb测年结果显示,钾长花岗岩年龄为429Ma,并含有405Ma的锆石;花岗闪长岩年龄为411Ma,并含432Ma的碎屑锆石;花岗闪长斑岩主体年龄为410.5Ma。研究区经历了3期岩浆与热液活动,且至少在早志留世就已开始,琼河坝岛弧是开始于早古生代的岛弧。辉钼矿Re-Os等时线年龄为409Ma,与花岗闪长斑岩年龄一致。和尔赛斑岩铜矿的主成岩成矿时代为早泥盆世,年龄约为410Ma。和尔赛铜矿的花岗闪长岩和花岗闪长斑岩具有埃达克岩与岛弧岩浆岩的地球化学特征,包括63.79%～68.86%SiO2、14.91%～17.48%Al2O3、0.68%～2.35%MgO、高Sr(383×10-6～971×10-6)与Sr/Y比值(48.3～111)、低Y(7.92×10-6～9.69×10-6)与Yb(0.76×10-6～0.98×10-6),Ba、U、K、Sr等大离子元素富集,Th、Nb、Ta、Ti等高场强元素亏损,较低的(87Sr/86Sr)i值(0.703852～0.704565)、正的εNd(t)值(6.1～7.4)、与亏损地幔接近的较低的初始铅同位素比值((206Pb/204Pb)i=17.58～17.91,(207Pb/204Pb)i=15.40～15.48,(208Pb/204Pb)i=37.25～37.47)。这些地球化学特征说明其形成于岛弧环境,可能为古俯冲洋壳部分熔融的产物。琼河坝地区以花岗闪长岩和花岗闪长斑岩为代表的岩浆岩带是形成和寻找斑岩铜矿的有利地区。Hersai porphyry copper deposit located at the eastern segment of the Yemaquan-Qiongheba Paleozoic arc belt,eastern Junggar was a new discovered copper deposit recently. The ore-forming intrusive body was granodioritic porphyry intruded in a granodiorite pluton containing irregular K-feldspar granitic bodies. Zircon U-Pb dating results show that the K-feldspar granite was older with weight average age of about 429Ma and contained some zircons with average age of about 405Ma,ages of the granodiorite and granodioritic porphyry were about 411Ma and 410.5Ma respectively,and the granodiorite had some clastic zircon with weight average age of about 432Ma. This indicates that there had experienced three-stages magmatic and hydrothermal actives from Early Silurian in the Hersai area,and the Qiongheba arc was created in the Early Paleozoic era. Re-Os isochron age of molybdenites was about 409Ma,which was consistent to that of the granodioritic porphyry in the Hersai area. This suggests that the porphyry copper deposit in the Hersai area was produced in the Early Devonian with an age of about 410Ma. Both the granodiorite and granodioritic porphyry in the Hersai area had typical geochemical feature of arc-type and adakitic intrusions,including 63.79%~68.86% SiO2,14.91%~17.48% Al2O3,0.68%~2.35% MgO,high Sr (383×10-6~971×10-6) and Sr/Y ratio (48.3~111),low Y (7.92×10-6~9.69×10-6) and Yb (0.76×10-6~0.98 ×10-6),enriched in large-ion lithophile element (e.g. Ba,K,Pb and Sr) and depleted in HSF elements (e.g. Th,Nb,Ti),low (87Sr/86Sr)i ratio (0.703852~0.704565),normal εNd(t) value (+6.1^+7.4),and low (206Pb/204Pb)i ratio (17.58~17.91),(207Pb/204Pb)i ratio (15.40~15.48) and (208Pb/204Pb)i ratio (37.25~37.47). These geochemical characteristics indicate that they were most possibly formed in arc setting and related to partial melting of subducted oceanic crust. The magmatic zone represented by granodiorite and granodioritic porphyry in the Qiongheba area is a potential area for formation and prospecting of porphyritic Cu depos

关 键 词：锆石U-PB定年 辉钼矿Re-Os等时线年龄 构造背景 斑岩铜矿 和尔赛 东准噶尔 

分 类 号：P618.41[天文地球—矿床学]