扬子西缘小相岭地区苏雄组古火山机构的发现及意义

通过详细的野外地质调查,发现扬子西缘小相岭地区苏雄组火山岩由巨厚的酸性-中酸性熔岩、火山碎屑岩和少量基性熔岩组成,在小相岭山脊两侧首次厘定4处古火山机构.其中,阳糯雪山古火山机构最壮观,是由火山颈相、溢流相、爆发相和火山沉积相构成的完整古火山机构.通过系统的地质剖面研究,发现该古火山机构存在2次喷发亚旋回和15个火山韵律,2次喷发亚旋回之间出现了1次明显的火山间歇期.小相岭地区古火山机构的发现,进一步厘定了苏雄组火山岩的喷发方式和构建特征,对进一步研究苏雄组酸性火山碎屑岩的起源及新元古代陆内裂谷作用具有重要意义.

Discovery and significance of Suxiong Formation ancient volcanic apparatus in Xiaoxiangling area of western Yangtze Block

The detailed geological survey shows that Suxiong Formation in Xiaoxiangling area of western Yangtze Block, consists of thick acid-intermediate acid lavas, volcaniclastic rocks and a small amount of basic lavas. And for the first time, four ancient volcanic apparatuses were found on both sides of the ridge of Xiaoxiangling Mountain. The volcanic apparatus in Yangnuo Snow mountain is the most grand, typical and complete sight and consists of volcanic neck facies, effusive facies, explosive facies and volcanic sedimentary facies. Systematic study of geological profile revealed that there were two eruption cycles, including fifteen volcanic rhythms, and there was a distinct period of volcanic intermission between these two eruption cycles. The discovery of these ancient volcanic apparatuses in Xiaoxiangling area can be used for further determination of volcanic eruption pattern and construction feature of Suxiong Formation. And this discovery can be also of significant importance to the study of the source of acidic volcanic rocks of Suxiong Formation and intracontinental riftimg in Neoproterozoic Era.