摘要
河南省卢氏县八宝山岩体位于华北克拉通南缘东秦岭西段,岩体呈筒状,可能为古火山机构岩颈相的超浅成侵入体,成矿组合上为独特的以铁为主的多金属矿化。八宝山岩体边缘相为钾长花岗斑岩、中心相为黑云母二长花岗斑岩。二者的LA-ICP-MS锆石U-Pb年龄非常一致,分别为146.6±1.6Ma和145.9±1.9Ma,说明他们可能是同期岩浆侵入作用分异的产物。钾长花岗斑岩和黑云母二长花岗斑岩锆石Hf同位素组成特征也非常相似,εHf(t)值分别为-27.55～-20.71和-27.30～-21.90,tDM2值分别为1.80～2.93Ga和2.03～2.92Ga,表明该岩体的源区物质以壳源物质为主。综合分析表明,八宝山岩体可能是扬子俯冲陆壳部分熔融的作物,并可能混入少量的太华群和熊耳群的物质,其形成的地球动力学背景可能为俯冲碰撞后的伸展环境。
The Babaoshan granite intrusion in Lushi county, Henan province, is tectonieally located in the southern margin of North China Craton, on the western part of East Qinling orogen. The granite intrusion occurs as circular column which might have been the neck of volcanic edifice ; while the associated iron ore deposit with accompanying Cu-Mo-Pb-Zn mineralization makes it a unique target for metallogenetic investigation in East Qinling area. The Babaoshan granite intrusion is a zoned granitic stock consisting of syenogranite porphyry in the outer zone and biotite monzogranite porphyry in the inner zone. LA-ICP-MS zircon U-Pb determination indicates that the syenogranite por- phyry and biotite monzogranite porphyry are roughly coeval, formed at 146.6±1.6 Ma and 145.9± 1.9 Ma, re- spectively. Zircon Hf isotope compositions of the syenogranite porphyry and biotite monzogranite porphyry are proxi- mately identical, with exf（t） values vary in ranges of - 27.55 - - 20.71 and - 27.30 - - 21.90, with Hf crustal model ages（toM2） of 1. 80 - 2.93 Ga and 2.03 - 2.92 Ga, respectively, indicative of crustal origin. Considering the tectonic evolution and geochemical characteristics of the granite as well as other Mesozoic granites in the south- ern margin of North China Craton, we suggest that the Babaoshan granite along with other Mesozoic granites was most likely derived from partial melting of subducted crust of Yangtze Craton, and possibly with minor involvement of the Taihua Group and Xiong＇er Group under extensional tectonic regime following depression of the subduction- collision between the Yangtze and North China cratons.
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2013年第1期65-77,共13页
Geotectonica et Metallogenia
基金
国家重点基础研究发展计划(编号:2012CB416602)资助
