新疆尼勒克县圆头山后碰撞花岗斑岩的同位素年代学及地球化学特征  

Zircon U-Pb geochronology and geochemistry of post-collisional granitic porphyry from Yuantoushan,Nileke,Xinjiang

作　　者：李宁波[1,2,3] 牛贺才[1] 单强[1] 姜玉航[1,3] 曾令君[1,3] 杨武斌[1] 裴重举 

机构地区：[1]中国科学院广州地球化学研究所 矿物学与成矿学重点实验室,广州510640 [2]西北大学大陆动力学国家重点实验室,西安710069 [3]中国科学院大学,北京100049 [4]山东省第一地质矿产勘查院,济南250014

出　　处：《岩石学报》2013年第10期3402-3412,共11页Acta Petrologica Sinica

基　　金：国家自然科学-新疆联合基金(U1203291);国家重点基础研究发展计划(973计划)(2011CB808903);国家自然科学基金项目(41173040);西北大学大陆动力学国家重点实验室开放课题基金联合资助

摘　　要：圆头山黑云母花岗斑岩位于尼勒克县城南，岩体普遍发育的铜矿化，以中部碎裂带中矿化最强。岩石具有典型的斑状结构，斑晶由碱性长石和黑云母组成，基质以长石、云母和石英为主，并合有少量的硫化物。圆头山黑云母花岗斑岩的轻重稀土分馏明显，并且明显富集大离子亲石元素（LLLE）（除sr外）和Pb，同时亏损高场强元素（HFSE）和Nb、Ta、P、Ti，显示出弧火山岩的地球化学特征。圆头山黑云母花岗形成年龄为269±3Ma，其源区以具有弧火山岩特征的下地壳为主，同时含有少量的幔源物质，而且在岩体的侵位过程中有高（^87Sr／^86sr）i（0．706054～0．709228）和高Pb含量（5．05×10＾-6～32．5×10＾-6）的陆秃物质混梁。在下地元物质熔融过程中，位于下地元底邵的富水和成矿元索的MASH帝物质也被圈入，使原始岩浆富水和成矿物质。圆头山黑云母花岗斑形成于碰撞后阶段，岩石的形成主要受岩石圈地幔拆沉作用的控制，而岩石圈地幔的拆沉可能与中亚造山带的垮塌或塔里木地幔柱活动有关。The Yuantoushan biotite granitic porphyry intrusion is located at the southern Nileke. Copper mineralization prevalently occurs within the intrusion, especially in the shattered zone. The granite has typical porphyritic texture, where phenocrysts are composed of alkali feldspar and biotite, and matrix is mainly composed of feldspar, biotite, quartz and minor sulfide. Trace element patterns for the granite are significantly depleted in HSFE, Nb, Ta, P, Ti and enriched in Pb and LILE （except St）, indicating products of arc magmatism. Zircon U-Pb age for the granite is 269 ± 3Ma. According to its geochemical features, we inferred that the granite were derived from a source mainly is composed of the lower continental crust materials with minor mantle substance and the lower continental crust has similar geochemical features with arc magma. In addition, the Yuantoushan granite has high （^87 Sr/^86Sr）i ratios （0. 706054 to 0, 709228 ） and Pb contents （5.05 x 10^～ 6 ～32. 5 x 10^-6） indicate the occurrence of contamination of continental crust materials during its emplacement. The involvement of fertilized materials from the melting-assimilation-storage homogenization （MASH） zones, which settled in the bottom of lower continental crust, induced the primary magma of the Yuantoushan intrusion enriched in water and metals. The geochemical data of the Yuantoushan granite indicates it was formed at post-collision setting and controlled by a delamination of mantle lithosphere. The delamination could be induced by the collapse of Central Asian Orogenic Belt or by the activity of Tarim mantle plume.

关 键 词：黑云母花岗斑岩 碰撞后阶段 岩石圈地幔拆沉 下地壳 MASH带 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]