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An X--ray, EPMA, and oxygen isotope study of vermiculitized micas in the ultramafic rocks at Askos, Macedonia, Greece

机译:X射线,EPMA和氧同位素研究了希腊马其顿Askos的超镁铁质岩石中的ver云母

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Extensive metasomatic zones of vermiculite-, tremolite--, chlorite-, and talc-rich rocks have been developed at the contacts of serpentinized ultramafic bodies and surrounding two-mica gneisses in the Askos area, Macedonia, Greece. These zones are probably related to the intrusion of acid magmatic bodies in the area. X-ray and EPMA studies confirmed the formation of vermiculite through a layer-by-layer transformation of original micas. In decreasing abundance, the following mixed--layer and discrete phases were identifiedf biotite/trioctahedral vermiculite (hydrobiotite), biotite/smectite, trioctahedral chlorite/trioctahedral vermicuIite (corrensite), vermiculite/smectite and discrete biotite, vermiculite, chlorite and talc. The 2--20 μm fraction of the vermiculitic samples consists mostly of biotite/vermiculite (> 40/100) with the biotite percentage dominating in the mixed phase. Lower abundances (20--40/100) of biotite/smectite and chlorite/vermiculite occur in both finer fractions (2--20 and < 2 pm) of all vermiculitic samples. Vermiculite/smectite is very abundant in the < 2 μm fractions of most vermiculitic samples. The DTA curves of the samples analyzed are characteristic of Mg-vermiculites. The electron micro- probe analyses show a gradual K leaching from precursor mica with increasing degree of weathering. Oxygen isotope results confirm this assumption. Initially, hydrothermal fluids derived from the neighboring granitic intrusions, were responsible for the micatization of the primary minerals of the ultramafic bodies. Hydrothermal activity was also responsible for the partial formation of corrensite. Consequently, water moving downwards was very important for the formation of the vermiculite and other clay mineral mixed-layer phases through the alteration of micas and chlorite. The low relief and the long-lasting tectonic stability of the area were essential
机译:在希腊马其顿的Askos地区,蛇纹石化的超镁铁质岩体和周围的两云母片麻岩的接触面已经形成了of石,透闪石,绿泥石和滑石的广泛的交代带。这些区域可能与该地区酸性岩浆体的侵入有关。 X射线和EPMA研究证实了通过原始云母的逐层转化形成of石。在减少的丰度中,鉴定出以下黑云母/三八面体bio石(水黑云母),黑云母/蒙脱石,三八面体亚氯酸盐/三八面体ren石(堇青石),s石/蒙脱石和黑云母,and石和绿identified石。 -20石样品中的2--20μm部分主要由黑云母/ ver石(> 40/100)组成,黑云母百分比在混合相中占主导地位。在所有ver石样品的两个较细级分(2--20和<2 pm)中,黑云母/蒙脱石和亚氯酸盐/ ver石的含量较低(20--40 / 100)。在大多数ver石样品的<2μm分数中,石/蒙脱石非常丰富。分析样品的DTA曲线是M石的特征。电子探针分析表明,随着风化程度的增加,从前体云母中逐渐浸出钾。氧同位素结果证实了这一假设。最初,来自邻近花岗岩侵入体的热液导致超镁铁质岩体的主要矿物的微晶化。水热活动也导致了堇青石的部分形成。因此,向下移动的水对于通过改变云母和亚氯酸盐形成the石和其他粘土矿物混合层相非常重要。该地区的浅浮雕和持久的构造稳定性至关重要

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