摘要
板山坪岩体是北秦岭二郎坪群中的侵入岩。为了查明该岩体的成因,对该岩体进行了锆石U-Pb年代学、锆石原位Hf同位素研究以及矿物化学分析等方面的研究。研究结果表明,板山坪岩体岩性组成主要为石英闪长岩和花岗闪长岩,花岗闪长岩内部存在暗色包体。本次研究获得板山坪石英闪长岩锆石U-Pb年龄为442.7~432.2 Ma,花岗闪长岩锆石U-Pb年龄为436.8~432.7 Ma,暗色包体锆石U-Pb年龄为437.6 Ma。锆石176Hf/177Hf值为0.282 737~0.282 736,εHf(t)值集中分布在8.4~9.4之间,二阶段Hf模式年龄(TDM2)在876~832 Ma之间。石英闪长岩结晶温压分别为673 ℃~745 ℃和0.19~0.54 GPa,花岗闪长岩结晶温压分别为657 ℃~730 ℃和0.48~0.96 GPa,暗色包体结晶温压分别为680 ℃~734 ℃和0.69~1.65 GPa。综合分析认为板山坪岩体为复式岩体,两期结晶年龄分别为496~487 Ma和442~432 Ma。岩石来源于地幔分离出来的新生下地壳。
The Banshanping pluton is an intrusive rock in the Erlangping Group of the North Qinling. The lithology is mainly quartz diorite and granodiorite. We present zircon U-Pb isotope chronology, mineral chemical analysis and Hf isotopes to study the genesis. The pluton is mainly composed of quartz diorite and granodiorite, and dark inclusions exist in granodiorite. The zircon U-Pb age of the Banshanping quartz diorite is 442.7~432.2 Ma, the zircon U-Pb age of the granodiorite is 436.8~432.7 Ma, and the dark inclusion zircon U-Pb age is 437.6 Ma. The Hf isotopes results show that the 176Hf/177Hf values of the zircons are between 0.282 737~0.282 736, and the εHf(t) values of the zircons are between 8.4 and 9.4, and the two stage Hf model age ranging from 876~832 Ma. The crystallization temperatures and pressures of quartz diorite are 673 ℃~745 ℃ and 0.19~0.54 GPa, granodiorite 657 ℃~730 ℃ and 0.48~0.96 GPa, dark inclusion 680 ℃~734 ℃ and 0.69~1.65 GPa, respectively. According to the comprehensive analysis, the Banshanping pluton is a complex rock mass, and the two phases of crystallization age are 496~487 Ma and 442~432 Ma, respectively. The rock is derived from the new lower crust that is separated from the mantle.
作者
李振强
任升莲
董树文
李龙明
李加好
葛粲
杨青亮
王静雅
Li Zhenqiang;Ren Shenlian;Dong Shuwen;Li Longming;Li Jiahao;Ge Can;Yang Qingliang;Wang Jingya(School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009;School of Electronic Science and Engineering, Nanjing University, Nanjing 210093)
出处
《地质科学》
CAS
CSCD
北大核心
2019年第3期973-999,共27页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金项目(编号:41572177,41272213)资助。
