摘要
长江中下游燕山期侵入岩由扬子型燕山早期、扬子型燕山晚期和江南型燕山期三个系列组成。在△γ -△β图解上 ,前两个系列侵入岩铅同位素参数均落入壳幔混合铅区 ,江南型燕山期侵入岩铅同位素参数散布于壳源铅区。Rb -Sr同位素锶初始比值 (Io)的变化特点是扬子型燕山早、晚期系列侵入岩的Io分别为 0 .6 994～ 0 .70 92和 0 .70 43～ 0 .70 82 ,除个别小于 0 .70 4外 ,均在 0 .70 4～ 0 .710之间 ;江南型燕山期系列侵入岩的Io为 0 .70 87～ 0 .7183,多数在 0 .710以上。在t-Io图解上 ,前二者均落入壳幔混合源区 ,属于I型或壳幔同熔型 ;后者均落入地壳源区 ,属于S型或地壳重熔型。黑云母地球化学特征参数图解显示扬子型侵入岩中的黑云母大部分分布于镁黑云母区 ,与西昌基性 -超基性岩相同 ,具有壳幔混源特征 ;侵入岩中的黑云母则主要分布于铁叶云母区 ,具有地壳重熔型岩浆岩特点。稀土元素方面 ,扬子型燕山期系列侵入岩中钙碱性岩稀土配分模式特点相同 ,属轻稀土强烈富集的平滑向右倾斜型曲线 ,而晚期系列中的正长岩却具有强烈的Eu负异常和弱到中等程度的Ce异常 ;江南型燕山期侵入岩为右倾斜率较小、分异程度差、Eu强烈亏损的稀土配分模式。
Yanshanian intrusions in the middle-lower reaches of Changjiang River is made up of early and late Yanshanian intrusion series of Yangzi type and Yanshanian series intrusion of Jiangnan type.Early and late Yanshian intrusion series of Yangzi type lead isotopic parameters all lie in the crust-mantle mixture origin area ,and Yanshanian series intrusion of Jiangnan type lead isotopic parameters in crust origin area in the △γ-△β diagram. The characterics of I o are :they are dividely 0.6994-0.7092, 0.7043-0.7082 in the early and late Yanshanian intrusions of Yangzi type, and 0.7089-0.7183 in Yanshanian intrusions of Jiangnan type. The former belongs to I type , the later belongs to S type. The geochemical characterics of biotite show that most biotite in intrusions of Yangzi type is Mg-biotite, with crust-mantle mixture origin feature; and that in intrusion of Jiangnan type is Fe-foliar mica, with crustal melted type feature. In the result of the above studies , the intrusions in Yanshanian series of Yangzi type are crust-mantle mixture origin,the intrusions in Yanshanian series of Jiangnan type are crust origin.
出处
《资源调查与环境》
2002年第1期52-59,共8页
Resources Survey & Environment
关键词
长江中下游
燕山期侵入岩
壳幔混合源区
壳源区
地球化学特征
初始比值
middle-lower reaches of Changjiang River
Yanshanian intrusion
crust-mantle mixture origin
crust origin
geochemical characterics
initial ratio
