Chemical and isotopic evidence for major mass transfer between mafic enclaves and felsic magma
Chemical and isotopic evidence for major mass transfer between mafic enclaves and felsic magma
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DOI：
10.1016/0009-2541(91)90053-t
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发表时间：
1991-09
期刊：
影响因子：
3.9
通讯作者：
P. Holden;A. Halliday;W. E. Stephens;P. J. Henney
中科院分区：
文献类型：
--
作者：
P. Holden;A. Halliday;W. E. Stephens;P. J. Henney
在Strontian和Criffell分带花岗岩类深成岩体中，某些化学元素(特别是K、Rb、Ca、Sr和Pb)在微闪长岩包体中的浓度与其在直接包裹的寄主花岗岩中的浓度之间存在相关性。这似乎代表了合并后飞地与其寄主岩浆之间的混合和交换的影响。包体初始的87Sr86Sr比值与主岩的比值没有区别，而包体143Nd144Nd的比值系统地更具放射性成因，表明这些包体既不是熔体分离，也不是重晶石。同位素数据与化学数据一致，表明尽管有明显的碱金属、碱土和过渡金属主要传质的证据，但锶几乎全部来自宿主，通过对比HFSE和REE的浓度和比例，以及与一些潜在起始原岩的Nd同位素比值，可以肯定地识别包体前驱体。在这方面，飞地的HFSE和REE组成可能允许通过将地幔来源的高温岩浆注入地壳而产生花岗岩类的模型进行测试。
In both the Strontian and Criffell zoned granitoid plutons, certain chemical elements (notably K, Rb, Ca, Sr and Pb) display a correlation between their concentration in microdiorite enclaves and their concentration in the immediately enclosing host granitic rock. This appears to represent the effects of post-incorporation mixing and exchange between the enclave and its host magma. Enclave initial 87 Sr 86 Sr ratios are indistinguishable from those of the host, while enclave initial 143 Nd 144 Nd ratios are systematically more radiogenic establishing that these enclaves are not melt segregations nor restite. The isotopic data are in agreement with the chemical data in indicating that Sr is almost entirely derived from the host Despite clear evidence of major mass transfer of alkali metals, alkali earths and transition metals, a comparison of the concentrations and ratios of HFSE and REE, and Nd isotopic ratios with those of a number of potential starting protoliths, allows the enclave precursors to be positively discriminated. In this regard enclave HFSE and REE compositions may allow for models of granitoid production by the injection of hot, mantle-derived magmas into the crust to be tested.