青海省查查香卡地区晚三叠世火山岩岩石学及其构造环境

STUDY ON VOLCANIC ROCKS AND THEIRSTRUCTURAL ENVIRONMENT OF LATETRIASSIC EPOCH IN CHACHAXIANGKAAREA IN QINGHAI PROVINCE

通过对查查香卡地区晚三叠世火山岩岩石学特征、空间分布、形态、火山机构、火山岩与构造关系的研究,确定该套火山岩时代为晚三叠世。岩石地层单位为鄂拉山组,为一套陆相喷发火山岩,呈NW向展布于大海滩-都库隆瓦地区。以中-高钾、高钙、低钛为特征,属钙碱性系列。火山喷发活动由强到弱,岩性由中性向中酸性渐变,岩浆活动由喷发型向侵入型递进。表明岩石构造环境为陆内消减带火山岩中的造山区。是来自地壳下部的火山岩浆经分异结晶并在上涌过程中混入有上地壳物质而喷发形成。喷出时的大地构造环境为陆内造山环境,该火山岩最初可能形成于大陆边缘环境,由于A型俯冲构造活动,测区乃至鄂拉山地区产生一系列右旋走滑断裂带,受NW向右旋走滑断裂的影响,岩石孔隙加大,并出现强烈的热流活动,导致岩浆沿这些断裂带喷出地表。

By studying the petrology, the space distribution, the volcanic mechanism, the relationship between the volcanic rock and the intrusive rock of late Triassic Epoch, and the structural zone around Chachaxiangka,the age of the volcanic rock is late Triassic Epoch.The rock stratum unit is Ngoloshan Group. It is a suit of continental eruption volcanic rock, distributing toward NW direction in Dahaitan-Dukulongwa area. Medial-high potassium, high calcium, low titanium, subordinating tocalc-alkaline series.Volcanic eruption acted from strong to weak as medium rocks became gradually into medium-acid rocks in Lithology, and extrusion changed into intrusion in magma activity. The volcanic rocks of Caidamu basin.And being a part of Dulan-Elashan moutain volcanic eraption belt in eastern Kunlun volcanic belt of late Triassic Epoch. This indicates the tectonic environment is orogenic belt region in consume zone. It is formed when magma of the lower Earth's crust streams up,while mingled with the material of the upper Earth's crust, and erupted finally. Tectonic environment belongs to orogenic environment. The volcanic rocks may be formed in continental marginal environment, as a result of A-type subduction,brought a series of dextral rotation strick-slip fault zone,apetuer of rocks became larger, and emerged intense hot fluid,caused magma erupted to the earth's surface from these fault zone.