德钦羊拉地区火山岩形成的构造环境讨论

A DISCUSSION ON THE STRUCTURAL ENVIRONMENT FOR FORMING THE VOLCANIC ROCK IN YANGLA REGION OF DEQIN

羊拉地区的火山岩分为块状和层状两类，它们分别形成于早石炭世和晚石炭世；块状火山岩呈单一拉斑玄武岩组合，层状火山岩的岩石类型以拉斑玄武岩和角闪安山岩为主，形成玄武岩－安山岩岩石组合；块状火山岩具准洋脊型火山岩特征，层状火山岩与大陆裂谷型火山岩特征一致；火山岩形成的构造环境，是在扬子地块西缘基础上发展起来的裂谷洋盆，块状火山岩发育于裂谷洋盆中央（准洋脊），层状火山岩则发育于裂谷洋盆的陆缘斜坡（次大陆）。

Abstract The volcanic rocks in the Yangla region can be classified into two types of massive and bedded, which were separately formed in Early or Late Carboniferous. The massive volcanic rock formed the simple tholelite assemblage. The bedded volcanic rocks formed the basalt--andesite assemblage, mainly tholelite and amphibole andesite. The massive volcanic rocks are with characteristics of paraoceanic ridge volcanic rocks whereas the bedded ones are consistent with those of the land rift volcanic rocks. The structural environment forming the volcanic rocks was a rift ocean basin developed along the west margin of the Yangzi Massif. The massive volcanic rocks were developed in the centre of the rift ocean basin but the bedded ones were developed on the epicontinental slope(subcontinent). And the Yangla Cu deposit is a massive sulphide deposit related to the rift ocean basin volcanics.