【摘要】 白芒山辉石闪长岩体位于安徽铜陵狮子山矿田内,属于高钾钙碱性岩系,形成时代为燕山晚期.运用Sr、Nd、Pb和O同位素综合示踪技术,探讨了该岩体的成因.研究结果表明,白芒山辉石闪长岩锶同位素初始值(ISr)变化于0.707291~0.707315之间;εNd(t)值变化于-13.04~-14.01之间;全岩δ18O值为10.2‰~11.7‰;初始铅同位素组成(t=142.9Ma)为:(206Pb/204Pb)i=17.9790~18.3267,(207Pb/204Pb)i=15.5125~15.6578,(208Pb/204Pb)i=38.1000~38.2117.结合安徽沿江地区岩浆岩研究资料可以看出,白芒山辉石闪长岩体为壳、幔岩浆混合成因,成岩物质起源于扬子下地壳和富集岩石圈地幔的部分熔融,是富集岩石圈地幔和扬子下地壳物质混合的产物,成岩过程后期经历了上地壳物质的混染作用影响.其中富集岩石圈地幔的形成主要与俯冲洋壳与陆壳析出流体的混染与交代作用有关.更多还原

【Abstract】 Baimangshan pyroxene diorite, which is located in Shizishan orefield, Tongling area, Anhui Province, belongs to high K calc-alkali series intruded in late Yanshanian. In this paper, the combined Sr, Nd, Pb and O isotopic composition tracing has been studied to discuss the genetic mechanism of the intrusion, and the results are as follows:(1)( ~ 87 Sr/ ~ 86 Sr)_i ratios vary from 0.707 291 to 0.707 315;(2)ε_ Nd (t)value ranges between -13.04 and -14.01; (3)δ~ 18 O value is between 10.2 ‰and 11.7 ‰;(4) as t = 142.9Ma, the ratios of ( ~ 206 Pb/~ 204 Pb)_i , ( ~ 207 Pb/~ 204 Pb)_i and( ~ 208 Pb/~ 204 Pb)_i vary from 17.979 0 to 18.326 7, from 15.512 5 to 15.657 8 and from 38.100 0 to 38.211 7, respectively. Together with the former relevant study on the intrusions in the along-Yangtze-river area of Anhui Province, we can conclude that the genesis of Baimangshan pyroxene diorite was the magma mixing of the crust and mantle materials. The source materials originated from the partial melting of the Yangtze lower crust and enriched lithospheric mantle, then generated from the mixing process of the enriched lithospheric mantle and Yangze lower crust. On one hand, the involvement of upper crustal materials had played an important role in the late magmatic evolution. On the other hand, the formation of the enriched lithospheric mantle was subjected to the involvement of the contamination and metasomatism by fluids from the subducted oceanic or continental crust materials.更多还原