Petrochemistry and petrogenesis of the Malani igneous suite, India: Discussion and reply
Petrochemistry and petrogenesis of the Malani igneous suite, India: Discussion and reply
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DOI：
10.1130/0016-7606(1982)93
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发表时间：
1981-02
影响因子：
4.9
通讯作者：
H. S. Pareek
中科院分区：
文献类型：
--
作者：
H. S. Pareek
“马拉尼层”是W.T.Blanford(1877)对拉杰普塔纳(现在的拉贾斯坦邦)西部的一系列火山岩的称呼，特别是在当时印度马尔瓦尔(焦特普尔邦)的马拉尼地区(Krishnan和Jacob，1956)。随后，这些岩石被描述为“马拉尼火山岩系列”(La Touche，1902)、“马拉尼体系”(Coulson，1933)、“马拉尼花岗岩和火山岩套”(Pascoe，1959)，它们现在被归入“马拉尼火成岩套”，以将所有熔岩和伴生岩石组合在一起。虽然头盔的名字“Malani”现在在印度调查拓扑表中是不存在的，它只出现在度表40 0上，名为anti Mallani RS(火车站)(25°43 i 45°N；71°21 iE)，6.4公里。在拉贾斯坦邦巴默区巴默市西南偏西，这些长英质岩石主宰了拉贾斯坦邦西部(图1)。它们的范围约为51,000平方公里，可能有10万平方公里被寒武纪和侏罗纪的沉积岩覆盖(Pareek，1980a)。因此，马拉尼火成岩套的总面积可能超过151,000平方公里，这些岩石有可能延伸到古吉拉特邦北部。马拉尼火成岩套最初的火山期由喷出的长英质熔岩组成-马拉尼凝灰岩和流纹岩，其次是深成侵入岩-Siwana和Jalor花岗岩，它们是同源岩浆。暴饮者和侵入者之间的差距在时间上并不是很分开(La Touche，1902；Coulson，1933)。形成的总体顺序是(1)马拉尼流纹岩、凝灰岩和沉积岩；(2)花岗岩；(3)斑岩；(4)石英脉(Pascoe，1959)。溢流岩和侵入岩被许多长英质、中基性和基性岩脉切割。在Sankra地区将其划分为五个阶段：第一阶段为流纹岩和带灰层的流纹岩斑岩；第二阶段为侵入岩-花岗岩；第三阶段为凝聚酸流；第四阶段为长英质岩石；第五阶段为基性喷发(Bhushan，1973)。因此，马拉尼火成岩套由(1)喷出相--流纹岩及其伴生的熔岩、凝灰岩、焊接凝灰岩和镁铁质岩组成；(2)由花岗岩组成的侵入相；(3)产生榴辉岩、闪长岩、辉长岩、玄武岩、流纹岩、粗面岩、安山岩、花岗岩、长英岩和石英脉的脉岩相；这一序列完成了Hatch和其他人(1961)所概述的“火成旋回”。
“Malani Beds” was the name given by W. T. Blanford (1877) for a series of volcanic rocks in western Rajputana (now Rajasthan) especially well developed in what was then the Malani district of Marwar (Jodhpur) State, India (Krishnan and Jacob, 1956). Subsequently, these rocks were described under the terms “Malani Volcanic Series” (La Touche, 1902), “Malani System” (Coulson, 1933), “Malani Granite and Volcanic suite” (Pascoe, 1959), and they are now being included under the name “Malani igneous suite,” to group all of the lavas and the associated rocks. While the helmet name “Malani” is non-existent now in the Survey of India topo sheet, and it appears only on the degree sheet 40 0 as Anti Mallani RS (Railway Station) (25°43i 45°N; 71°21iE), 6.4 km. west-southwest of Barmer city, Barmer, district, Rajasthan, these felsic rocks dominate western Rajasthan (Fig. 1). Their extent is about 51,000 km 3 ; possibly 100,000 km 2 could be underlain by sedimentary rocks of Cambrian and Jurassic ages (Pareek, 1980a). The Malani igneous suite may thus have had a total spread of more than 151,000 km 2 , with the possibility of extension of these rocks into the northern part of Gujarat. The Malani igneous suite had an initial volcanic phase, made up of extrusive felsic lava outpourings—Malani Tuff and Rhyolite, followed by plutonic intrusions—Siwana and Jalor Granites, which are comagmatic. The gap between the effusives and intrusives was not much separated in time (La Touche, 1902; Coulson, 1933). The general order of formation was (1) Malani rhyolites, tuffs, and sedimentaries; (2) granite; (3) porphyries; (4) and quartz veins (Pascoe, 1959). The effusives and intrusives are cut by a number of felsic, intermediate, and mafic dikes. These have been divided into five phases in the Sankra area; the first phase is rhyolite and rhyolite porphyry with ash beds; the second phase is of intrusives, the granites; the third phase is of agglomeratic acid flow; the fourth phase is of felsic rocks; and the fifth phase is of basic eruption (Bhushan, 1973). The Malani igneous suite thus is composed of (1) an extrusive phase—rhyolites and associated lavas, tuff, welded tuff, and mafics; (2) an intrusive phase—made up of granites; and (3) a dike phase which produced dolerite, diorite, gabbro, basalt, rhyolite, trachyte, andesite, granite, felsite, and quartz veins; this sequence completes an “igneous cycle,” as outlined by Hatch and others (1961).