中国东部岩石圈上地幔的组成特征及其地质意义

无论是在岩石学领域,还是在地质学的其它研究领域,地幔的岩石学特征都具有十分重要的意义。本文试图把统计学方法引入区域岩石学研究,从中国东部新生代玄武质岩石中超镁铁岩包体的成分特征入手,应用统计学方法阐明中国东部岩石圈上地幔整体上为弱亏损上地幔的观点。并且认为,在中国东部,岩石圈上地幔具有东西分带的特点。地幔岩石的带状分布方向为NNE向,与中国东部上地幔隆起的长轴方向一致。从东向西可以分出3个带,即东南沿海带、长白山—郯庐断裂带及大兴安岭—太行山带。另一方面,岩石圈上地幔岩石成分的这种分带性又受到其它因素的影响,以致在东西分带的基础上显现南北分块的特征,大致划分出了东北、华北、华南三大地块,体现了中国东部岩石圈上地幔的南北差异。在这个基础上,进一步探讨了我国东部岩石圈上地幔的组成特征在玄武岩岩浆起源、裂谷作用及地质演化等方面的意义。

PETROLOGICAL CHARACTERS OF THE UPPER MANTLE BENEATH EASTERN CHINA AND ITS GEOLOGICAL IMPLICATIONS

Petrological characters of the mantle rocks are very important either to petrology or to the other branches of geology. In this paper, the author attempts to introduce a statistical method into the regional petrology. The petrolog?ical characters of the upper mantle beneath eastern China was discussed according to the composition of ultramac inclusions included in Cenozoic basaltic rocks in eastern China, It is pointed out that the uppr mantle in eastern China was a weakly depleted one and it is zoned compositionally in the direction of east-west. The orientation of the belts is NNE and is consistent with that of the major axis of the mantle bulge. Three belts have been recognized from the west to the east, namely: the Daxinganling?Taihangshan belt, the Changbai mountainangcheng-ujiang rift belt and the southeastern coastal belt. On the other hand, the zoning character of the upper mantle is also effected by other factors. Based on the compositional difference in the ward direction and the E ward zoning, the upper mantle beneath eastern China may be divided into three blocks: northeastern China block, nortn China block and south China block.