Zircon LA-ICP-MS U-Pb dating for diabase from Jiangshiqiao in Taojiang City of Hu'nan Province yielded an emplace?ment age of 229±2.3Ma (n=8,MSWD=1.8,2σ). The diabase is characterized by low values of potassium (K2O/Na2O=0.14~0.16), and alkali (K2O+Na2O=2.89%~2.96%) , enrichment of large ion lithophile elements and LREE and depletion of high field strength el?ements, low (87Sr/86Sr)i ratios (0.70606~0.70644),low positiveεNd(t) values (1.55~1.87) and enrichment of radioactive Pb, suggesting a mixed source of the depleted mantle (DM) and the lower crustal. In combination with previous studies, the authors hold that the di?abase was formed through partial melt of the mantle and lower crustal components by the upwelling asthenosphere during the Indo?sinian post-orogenic lithosphere extension in Hu'nan Province.%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(K2O/Na2O=0.14~0.16),贫碱(K2O+Na2O=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(87Sr/86Sr)i(0.706052~0.706437),较低正εNd(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.
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