Sm-Nd isotopic study of garnets and their metamorphic host rocks
Sm-Nd isotopic study of garnets and their metamorphic host rocks
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DOI：
10.1017/s0263593300013535
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
O. Breemen;C. Hawkesworth
中科院分区：
文献类型：
--
作者：
O. Breemen;C. Hawkesworth
摘要 在这项可行性研究中，确定了石榴石以及来自角闪岩相岩石、麻粒岩相岩石和榴辉岩的共存矿物和全岩相的 Sm/Nd 和 143Nd/144Nd 比率。在两种云母片岩和榴辉岩中，石榴石相对于其他相的 Sm/Nd 比的分配系数在 2-3 范围内，即与火成岩中斑晶的值相当。在两种麻粒岩相岩石中，石榴石相对于其他相的 Sm/Nd 分配系数在 13-20 范围内，并得出了精确的年龄。来自南部非洲林波波带麻粒岩相剪切带的石榴石，其太古宙年龄，已得出 1974±14 Ma 和 1988±14 Ma 的一致重复年龄。这些结果被解释为与该地区最后一次构造事件有关，距主要片麻岩形成事件很久之后。苏格兰米德兰山谷石炭纪喷口的麻粒岩相捕虏体中的石榴石，年龄为 356±10 Ma；这与该地区基本岩浆活动的爆发有关。
ABSTRACT In this feasibility study, Sm/Nd and 143Nd/144Nd ratios have been determined on garnets and coexisting mineral and whole-rock phases from a selection of amphibolite facies rocks, granulite facies rocks and an eclogite. In two micaceous schists and an eclogite the distribution coefficient of the Sm/Nd ratio in garnet relative to other phases is in the range 2-3, i.e. comparable to values for phenocrysts in igneous rocks. In two granulite facies rocks the garnets have Sm/Nd distribution coefficients relative to other phases in the range 13-20 and have yielded precise ages. Garnet from a granulite facies shear zone from the Limpopo belt in southern Africa, of Archaean age, has yielded concordant duplicate ages of 1974±14 Ma and 1988±14 Ma. These results have been interpreted as relating to the last tectonic event in the region, long after the main gneiss-forming event. Garnet from a granulite facies xenolith from a Carboniferous vent in the Midland Valley of Scotland has yielded an age of 356±10 Ma; this is related to the onset of basic magmatism in the region.