摘要
东准噶尔琼河坝桑德乌兰斑岩铜钼矿区含矿花岗斑岩透长石、石英斑晶粒内破裂构造发育,锆石普遍发育具核内破裂构造或碎裂状的核。破碎的锆石核与透长石、石英斑晶可能形成于深部岩浆房。锆石U-Pb定年结果显示,破碎变形的锆石核年龄为442.2±3.5Ma,锆石环带的年龄为412.7±3.3Ma,前者代表破碎变形锆石的形成时间,后者代表斑岩侵位与结晶的时间。Hf同位素结果显示,破碎的有核锆石与其外环带具一致的εHf(t)初始值与tDM2模式年龄,它们可能为同一岩浆或成因相同的岩浆不同阶段结晶的产物。这意味着琼河坝地区在早古生代(至少在442Ma)就开始有弧岩浆活动。幔源特征的εHf(t)值(10.3～15.1)与较老的模式年龄(tDM2=469～761Ma)显示形成研究区花岗斑岩的岩浆可能源于晚元古代-奥陶纪玄武质地壳的部分熔融。
Granite porphyry in the Sangdewulan copper-molybdenum district in the Qiongheba area,East Junggar was characterized by the abundance of sanidine and quartz phenocrysts with intragranular fractures and fractured core zircons,which was formed in a pre-emplacement magma chamber. Zircon U-Pb dating results suggest that the fractured zircons formed at age of about 442. 2 ± 3. 5Ma,and the rim zircons at about 412. 7 ± 3. 3Ma. The age of about 413Ma shows the time of emplacement and crystallization of the granite porphyry. Hf isotopic data of zircons suggest that the fractured cores and rim had a similar value of εHfand tDM2,and were most possibly derived from a same magma resources. This indicates that magmatic activity in the Qiongheba arc appeared at least from 442Ma in the Early-Paleozoic era. High εHf( t) value ( 10. 3 ～ 15. 1) and relative big model ages ( tDM2 = 469 ～ 761Ma) suggest that magma formed granite porphyry in the Sangdewulan district were likely derived from the remelting of Late-Proterozoic-Ordovician basaltic crust.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第8期2389-2398,共10页
Acta Petrologica Sinica
基金
中国科学院知识创新工程主要方向项目(KZCX2-YW-107)
"十一五"国家科技支撑计划重点项目(2006BAB07B01-03)
中国科学院矿产资源重点实验室基金联合资助
