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首页> 外文期刊>Journal of Asian earth sciences >~(40)Ar-~(39)Ar geochronology of the charnockites and granulites of the Kan Nack complex, Kon Turn Massif, Vietnam
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~(40)Ar-~(39)Ar geochronology of the charnockites and granulites of the Kan Nack complex, Kon Turn Massif, Vietnam

机译：〜（40）Ar-〜（39）Ar年代学，越南Kon Turn Massif的Kan Nack矿床的菱锰矿和花岗石

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摘要

The Truong Son Belt forms the eastern rim of the Indochina Block in Southeast Asia. The age of the metamorphism, mainly along NW-SE mylonitic shear zones that affects this belt, has been formerly determined at about 240-250 Ma. This age corresponds to the Indosinian tectonometamorphic episode. The Kon Turn Massif, situated to the south of this belt, comprises high-temperature rocks, the Kan Nack Complex, including charnockites and granulites. The main charnockitic outcrops, restricted to the Song Ba Valley, establish the intrusive nature of these magmatic rocks within granulite facies material. Basic charnockitic rocks are mainly quartz enderbites to norites and hornblende-pyroxene granulite facies rocks. The ~(40)Ar-~(39)Ar age of intrusion-cooling of charnockitic magmas is determined from primary magmatic biotites at about 245 Ma. In the east of the Kan Nack Complex some granulite facies rocks exhibit relicts of primary granulite facies parageneses, whereas others show evidence of overprinting by a retrogressive low-grade metamorphism. Ar-Ar dating confirm this evolution, giving ages of 400 Ma for primary relict granulite facies phases and 260-270 Ma from the most retrogressed samples establishing the youngest limit for the granulite facies metamorphism. Granulites intruded by charnockites in the Song Ba Valley yield ages of about 250 Ma, equivalent to the ages of the charnockites, and have evidently been completely reset by these high temperature intrusions. Therefore, the Kan Nack Complex of the Kon Turn Massif is not an independent unit with respect to the Indosinian orogen, but represents the deep-crustal part of this belt.
机译：Truong Son带形成了东南亚印度支那地区的东部边缘。变质的年龄，主要是沿着影响该带的NW-SE髓质剪切带，以前已确定为约240-250 Ma。这个年龄对应于印支期构造变态事件。位于该带以南的Kon Turn地块包括高温岩石，即Kan Nack复合体，其中包括菱镁矿和花岗石。限定在松坝河谷的主要岩性露头在粒岩相材料中建立了这些岩浆岩的侵入性。碱性的蛇纹岩主要是对钠长石的石英quartz石和角闪石-辉石-花岗石相岩。岩浆岩浆侵入冷却的〜（40）Ar-〜（39）Ar年龄是由约245 Ma的原生岩浆黑云母确定的。在Kan Nack构造体的东部，一些花岗石相岩石显示出原始花岗石相的亚种遗迹，而另一些则显示出倒退性低品位变质的叠印证据。 Ar-Ar定年证实了这一演化，给出了主要遗迹粒状相相的年龄为400 Ma，最落后的样品中年龄为260-270 Ma，为粒状相变质建立了最小限度。在松坝河谷中，煤灰岩侵入的花岗石年龄约为250 Ma，与菱形岩的年龄相当，显然已被这些高温侵入完全重置。因此，Kon Turn地块的Kan Nack复合体不是关于印度支造山带的独立单元，而是代表了该带的深壳部分。

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