湖南桃江地区印支期辉绿岩成因——地球化学、年代学和Sr-Nd-Pb同位素约束

发布时间：2018-05-14 23:28

本文选题：辉绿岩 + 地球化学　；参考：《地质通报》2017年05期

【摘要】：对湖南桃江地区江石桥辉绿岩进行了LA-ICP-MS锆石U-Pb定年,获得的岩浆侵位年龄为229±2.3Ma(n=8,MSWD=1.8,2σ)。其低钾(K_2O/Na_2O=0.14~0.16),贫碱(K_2O+Na_2O=2.89%~2.96%),富集大离子亲石元素(Rb、Ba、Th、U),亏损高场强元素(Nb、Ta、Ti),呈轻稀土元素弱富集,无Eu、Ce异常,富集放射性成因Pb,低(~(87)Sr/~(86)Sr)_i(0.706052~0.706437),较低正ε_(Nd)(t)(1.54~1.86)的特征,表明岩石来源于下地壳物质和亏损地幔的混合源区。综合前人的研究结果认为,在印支运动造山后的伸展背景下,软流圈上涌导致区域下地壳及部分地幔物质发生熔融,形成辉绿岩岩浆并向上侵位而成。
[Abstract]:The LA-ICP-MS zircon U-Pb dating of Jiangshiqiao diabase in Taojiang area, Hunan Province has been carried out, and the magmatic emplacement age is 229 卤2.3 Mai ~ (2) Ma ~ (2) Ma ~ (8) M _ (WD) ~ (1. 8) ~ (2) 蟽 ~ (-1). Its K _ 2O / Na _ 2O _ O _ O _ (0.14) and K _ 2O / Na _ 2O _ O _ (0.16), alkali-poor K _ 2O / Na _ 2O _ 2O _ 2 2.89 ~ 2.96 and large ion _ lipophilic elements Rb-Ba-Ba _ T _ U _ UT _ UT _ T _ T _ T _ T _ T _ T _ T _ T _ T _ _ _ It is suggested that the rocks originated from the mixed source of the lower crust and depleted mantle. Based on the results of previous studies, it is concluded that in the context of post-orogenic extension of the Indosinian movement, the upwelling of the asthenosphere leads to the melting of the lower crust and some mantle materials in the region, resulting in the formation and emplacement of diabase magma.
【作者单位】：中国地质调查局武汉地质调查中心;中国地质调查局花岗岩成岩成矿地质研究中心;湖南省地质矿产勘查开发局四一三队;
【基金】：中国地质调查局项目《雪峰古陆及邻区金刚石找矿选区评价》(编号:12120113063000) 国家自然科学基金项目《粤北大宝山多金属矿床成因研究》(批准号:41302068)
【分类号】：P581;P597

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