西天山达巴特矿区火山岩的形成时代、构造背景及对斑岩型矿化的制约  

Ages and tectonic settings of the volcanic rocks in Dabate ore district in West Tianshan Mountains and their constraints on the porphyry-type mineralization

作　　者：张作衡[1] 王志良[1] 左国朝[2] 刘敏[1] 王龙生[1] 王见蓶 

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]甘肃省地质调查院,兰州730000 [3]新疆有色地勘局七0三地质队,新疆伊宁835100

出　　处：《地质学报》2008年第11期1494-1503,共10页Acta Geologica Sinica

基　　金：国家自然科学基金资助项目(编号40573028);地质调查项目(编号1212010561603-3和1212010634001);国家科技支撑重(编号2006BAB07B08-01)资助的成果

摘　　要：本文通过对西天山地区比较典型的达巴特斑岩铜钼矿床矿区范围内出露的英安岩和花岗斑岩进行了系统的岩石地球化学分析,对流纹斑岩和花岗斑岩中的锆石进行了SHRIMPU-Pb定年研究,分别获得了315.9±5.9Ma和278.7±5.7Ma。岩石化学、微量以及稀土元素特征表明从英安岩到花岗斑岩,岩体具有明显的分异演化特征和很好的继承性。火山岩和次火山岩的精确定年为准确厘定火山岩形成的时限和地球动力学背景提供了依据。结合已有的Re-Os法获得的矿化年龄,表明晚石炭世末-早二叠世初(278.7±5.7Ma),西天山地区进入板块碰撞-板内伸展阶段,由于深源岩浆侵位,在达巴特矿区形成了由花岗斑岩、流纹斑岩和流纹质角砾熔结凝灰岩组成的椭圆形火山机构,并导致相关矿床的形成。This paper carried out chemical analysis on the dacite and granite-porphyry and SHRIMP zircon U-Pb dating on rhyolitic porphyry and granite-porphyry from the Dabate ore district and adjacent area. The diagenetic ages of rhyolitic porphyry and granite-porphyry are 315. 9± 5. 9Ma and 278. 7±5. 7Ma, respeetively. Analysis result of lithochemisty, trace elements, and REE shows that both dacite and granite-porphyr are characterized by distinct differentiation and good inheritance. Accurate dating for volcanic and sub-volcanic rocks provides reliable data to constrain the geodynamic settings and timing of volcanic rock formation. Combined with the Re-Os dating data for mineralization obtained previously, it is concluded that during late Carboniferous to early Permian （278.7 ± 5.7Ma）, the West Tianshan began to the stage of interplate collision and intraplate extension. The emplacement of deep-derived porphyry magma formed oval volcanic apparatus which consists of granite-porphyry, rhyolitic porphyry and rhyolitic breccia welded tuff, and further resulted in the formation of Dabate porphyry copper molybdenum deposit.

关 键 词：达巴特 火山岩 岩石地球化学 SHRIMP锆石U—Pb定年 西天山 

分 类 号：P597.3[天文地球—地球化学]