Timing of magmatic and metamorphic events in the Jijal complex of the Kohistan arc deduced from Sm-Nd dating of mafic granulites
Timing of magmatic and metamorphic events in the Jijal complex of the Kohistan arc deduced from Sm-Nd dating of mafic granulites
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根据镁铁质麻粒岩的 Sm-Nd 测年推断科希斯坦岛弧 Jijal 杂岩岩浆和变质事件的时间
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
E. Nakamura
中科院分区：
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作者：
H. Yamamoto;E. Nakamura
吉贾尔杂岩东北部的镁铁质-超镁铁质麻粒岩包括二辉麻粒岩、石榴单斜麻粒岩和石榴角闪石岩。野外和结构关系表明，二辉麻粒岩是石榴单斜麻粒岩形成后的残留物，石榴角闪石岩是切割基性麻粒岩原岩的原始侵入岩。测定了二辉麻粒岩、石榴单斜麻粒岩和石榴角闪石岩的Sm-Nd矿物等时线年龄分别为118 ± 12 Ma、94.0 ± 4.7Ma和83 ± 10 Ma。这些年龄和以往报道的年代学资料表明：（1）麻粒岩原岩的结晶作用早于或与科希斯坦弧向亚洲大陆的构造增生作用同时代：（2）与增生作用有关的地壳增厚可能是吉贾尔杂岩高压麻粒岩相变质作用的原因;（3）石榴石角闪石岩组合的形成可能是在石榴石-单斜辉石麻粒岩结晶之后。
Abstract Mafic to ultramafic granulites in the northeastern part of the Jijal complex include two-pyroxene granulite, garnet-clinopyroxene granulite and garnet hornblendite. Field and textural relations indicate that two-pyroxene granulite is a relict left after formation of the garnet-clinopyroxene granulite and garnet hornblendite was an originally intrusive rock which dissected the protoliths of mafic granulites. Sm-Nd mineral isochron ages of 118 ± 12 Ma, 94.0 ± 4.7 Ma and 83 ± 10 Ma were determined for two-pyroxene granulite, garnet-clinopyroxene granulite and garnet hornblendite respectively. These ages, together with previously reported chronological data, led to the following tectonic implications: (1) crystallization of the granulite protoliths predates, or is coeval with, the tectonic accretion of the Kohistan arc to the Asian continent; (2) crustal thickening related to the accretion was probably responsible for the high-pressure granulite-facies metamorphism in the Jijal complex; (3) formation of the garnet hornblendite assemblage was probably after crystallization of garnet-clinopyroxene granulite.