Late-Orogenic, Post-Orogenic, and Anorogenic Granites: Distinction by Major-Element and Trace-Element Chemistry and Possible Origins
Late-Orogenic, Post-Orogenic, and Anorogenic Granites: Distinction by Major-Element and Trace-Element Chemistry and Possible Origins
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DOI：
10.1086/629406
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发表时间：
1990-05
期刊：
影响因子：
--
通讯作者：
J. Rogers;J. K. Greenberg
中科院分区：
文献类型：
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作者：
J. Rogers;J. K. Greenberg
仅根据产状构造和相关岩石类型将花岗岩分为四类，这些花岗岩也具有组内一致而组间不同的成分特征。与造山有关的花岗岩包括与钙碱性岩基有关的晚造山变种（LO）和后造山变种（PO），它们出现在最近变形的造山带中孤立的底辟深圳湾的广阔区域中。倾斜的稀土配分模式、中等的Sr含量和K2 O-SiO2关系表明，晚造山花岗岩是由钙碱性岩浆分异斜长石、单斜辉石和角闪石形成的。花岗岩的稀土元素配分模式较平坦，K2 O含量接近5%，且无岩浆岩伴生，表明造山后花岗岩是由俯冲作用产生的基性/中质岩浆岩部分熔融而成。晚造山期和造山后花岗岩都可能是造山作用向陆壳中新加入的物质。斜长岩/环斑杂岩（AR）或碱性环杂岩（RC）中的非造山花岗岩的LIL含量太高，无法与镁铁质矿物组合平衡。这些非造山岩石可能是先存硅铝质地壳部分熔融的产物，不代表新的地壳增量。
Granites classified into four categories based solely on tectonics of occurrence and associated rock types also have compositional characteristics that are consistent within groups and different among groups. Orogenically related granites include late-orogenic varieties (LO) associated with calc-alkaline batholiths, and post-orogenic varieties (PO), which occur in broad zones of isolated diapiric plutons in recently deformed orogenic belts. Inclined REE patterns, moderate Sr contents, and $$K_{2}O-SiO_{2}$$ relationships show that late-orogenic granites formed by fractionation of plagioclase, clinopyroxene, and amphibole from calc-alkaline magmas. Flatter REE patterns and $$K_{2}O$$ contents near 5%, plus the absence of associated magmatic rocks, indicate that the post-orogenic granites developed by partial melting of subduction-produced mafic/intermediate magmatic rocks. Both the late- and post-orogenic granites can be part of material newly added to continental crust as a result of orogeny. Anorogenic granites in anorthosite/rapakivi complexes (AR) or alkaline ring complexes (RC) have LIL contents too high to have been equilibrated with a mafic mineral assemblage. These anorogenic rocks probably formed by partial melting of preexisting sialic crust and do not represent new crustal increment.