Chapter V. 



BASIC AND ULTRABASIC INTRUSIVE ROCKS IN ASIA AND THE 



MALAY ARCHIPELAGO. 



Asia possesses a simpler structure than the smaller area of Europe, and basic intrusive 

 rocks are much less abundant, and are confined chiefly to the youngest folded series. The 

 foundation of Siberia is composed of gneisses and schists, and these extend eastward into Mon- 

 golia, Manchuria, and Korea, where they are overlain by Cambrian sandstones, and by widely 

 transgressive Devonian formations. Serpentines appear in the gneissic complex in Korea 

 (Schulz '10) and south of Lake Baikal (Suess III, p. 67). The Devonian sediments are locally 

 folded in eastern Siberia, and have been invaded by diorite and gabbro (Suess III, p. 123), 

 but to the southwest of Siberia they are overlain by lower Carboniferous rocks upon which 

 generally, though not always, the upper Carboniferous beds are strongly unconformable. In 

 the period of folding which, therefore, occured in Carboniferous times, there were intruded the 

 granites, syenites, and diorites of the Altai Mountains, in the contact zones of which are many 

 important ore bodies. Ultrabasic rocks are rarely described from these complexes, but ser- 

 pentines occur in the southeast of the Province of Akmolinsk {fide, J. M. Bell). According 

 to Loczy ('95), there were eruptions of greenstone and serpentine with porphyrite and amygda- 

 loidal diabase, following the formation of Carboniferous limestone in western China. These 

 perhaps may also be connected with the Altaid folding. 1 



Between these Carboniferous folds which surround the Siberian shield and the massifs of 

 Peninsula India and Arabia extend the great mountainous zone comprising the eastward con- 

 tinuation of the alpine mountain system, the former Tethyan geosyncline. The trend-lines 

 connecting the Balkan Peninsula and Asia Minor have been indicated by Naumann ('96), but 

 very little of the literature on this region has been accessible to the writer. In particular Freeh's 

 valuable summary ('16) was not available. Broadly speaking, Asia Minor consists of a central 

 plateau of faulted horizontal strata, while the surrounding ranges consist of intensely folded 

 strata. The oldest fossiliferous formations are Devonian, followed conformably by Carbonif- 

 erous rocks, but beneath these are areas of schists and limestones with talc-schists, serpentines, 

 peridotites, and granites. (Encyl. Britannica, 11th ed.) The ultrabasic rocks have been noted 

 at Samos (Spratt '47, Butz '12), Mitylene (Launay '90, '98), Mount Ida (Diller '83), and near the 

 Olympus of Brussa (WUkinson '95) . More definite, however, is the age of the serpentine lying far- 

 ther to the east. It extends through the Pontic Mountains in the Cicilian Taurus, and continuing 

 into the Ala Dagh is associated with Cretaceous limestone (Schaffer '00). Oswald ('11) shows 

 that it has a wide distribution in Armenia, there being two principal zones, the northern cres- 

 centic zone extending through Erzerum, along the headwaters of the Frat, and bending to the 

 east-southeast to follow the Goktsche and Pambek ranges. In this zone the serpentines are 

 associated with Jurassic, Cretaceous, and Lower Tertiary rocks. South of this there extends 

 a roughly parallel arcuate line of ultrabasic intrusions along the Taurus Mountains toward Lake 

 Umri. In this zone we find a continuation of the serpentine-zone of Cyprus. Oswald considers 



1 Devonian and Silurian rocks also occur, the latter consisting of clay-shales with chert interbedded with diabase and melaphyre-tuff . Since 

 the above was written Leuchs's ('16) account of Central Asia has been received. He states that a widespread orogeny occurred in pre-Devonian 

 time, accompanied by granite intrusions. The marine strata laid down in the Devonian transgression are very generally intercalated with diabase, 

 melaphyre, and basic tuff, and were folded at the close of Devonian time when an extensive orogeny occurred with intrusion of granite. After 

 the deposition of Lower Carboniferous marine beds there was a third period of mountain-building (the typical Altaid orogeny), in which a further 

 series of plutonic intrusions took place, on the eroded surfaces of which the Upper Carboniferous sediments now rest. Associated with the last 

 series of intrusions are numerous masses of gabbro in the Ala and Pa m ir ranges and particularly in the Tian Shan, while peridotite, pyroxenite, 

 and serpentine are known in the Tian Shan, the Tarbagati and especially in the western Kuen Lun ranges. 



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