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Determination of the Magnitude of Metasediment-Derived Melt Assimilation in the Southern Sierra Nevada Batholith

内华达山脉南部基岩中变沉积物衍生的熔体同化程度的测定

基本信息

批准号：
9815024
负责人：
Jason Saleeby
金额：
$ 10.3万
依托单位：
California Institute of Technology
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
1998
资助国家：
美国
起止时间：
1998-12-01 至 2001-11-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=9815024&HistoricalAwards=false
关键词：
Determination Magnitude Metasediment Derived Melt

项目摘要

9815024SaleebyThis study is a petrologic investigation of the high temperature metamorphism and migmatization of mid- crustal pelitic pendants from the southern Sierra Nevada batholith, California. The primary goals are: (1) determine the extent of partial melting of batholith metasedimentary pendants during the large scale plutonism, and (2) quantify the efficiency of two-component mixing between batholith- and pendant-derived melts and the incorporation of pendant melts into large granitoid plutons. This study is designed to test the importance of assimilation of pre-existing shallow crust in the mass budget of the composite batholith. The pelites of the study area underwent extensive high-grade metamorphism and local migmatization in response to the intrusion of large granitoid plutons during the late Cretaceous. The isotopic ratios of Sr, Nd, and O of the batholithic rocks and the compositionally uniform pelite are distinct in the area. Hence, these isotopic ratios will be used as the principal tool in order to: (1) distinguish between batholith-derived and pelite-derived melts, and (2) constrain the mixing between the two in both migmatitic leucosomes and within the batholith. Petrographic studies of mineral and melting reactions within the migmatitic pelite as well as major and trace element chemistry will complement the isotopic data. The significance of crustal hybridization of Cordilleran batholiths with partial melts from metasedimentary host rocks is a controversial topic with important applications to quantifying crustal recycling in Phanerozoic magmatic arcs. This study should put important constraints on the extent and limits of such assimilation and hybridization.

9815024Saleeby 这项研究是对加利福尼亚州内华达山脉南部岩基的中地壳泥岩悬垂物的高温变质作用和混合作用进行的岩石学研究。主要目标是：（1）确定大规模深成岩作用过程中岩基变沉积悬垂物部分熔融的程度，以及（2）量化基岩和悬垂熔体之间的双组分混合以及悬垂熔体并入大型花岗岩岩体中的效率。本研究旨在测试复合岩基质量预算中预先存在的浅地壳同化的重要性。研究区的泥岩在白垩纪晚期经历了广泛的高级变质作用和局部混合岩化作用，以响应大型花岗岩类岩体的侵入。该区岩基岩和成分均一的泥质岩的Sr、Nd、O同位素比值明显。因此，这些同位素比率将用作主要工具，以便：（1）区分岩基衍生的熔体和泥质岩衍生的熔体，以及（2）限制两者在混合岩无色体和岩基内的混合。对混合岩泥岩内的矿物和熔融反应以及主量和微量元素化学的岩相研究将补充同位素数据。科迪勒拉岩基与变沉积岩围岩部分熔体的地壳杂交的意义是一个有争议的话题，在量化显生宙岩浆弧的地壳再循环方面具有重要的应用。这项研究应该对这种同化和杂交的程度和限制施加重要的限制。