西藏sedex型矿床赋矿盆地性质对成矿元素的制约作用

The controls of the host basins on ore-forming elements from the sedex deposits in Xizang

关键词:  西藏  sedex型矿床  赋矿盆地  成矿元素

Key words:  Xizang  sedex deposit  host basin  ore-forming element

摘要:

“青藏高原热”的掀起,极大地提高了西藏境内基础地学的研究水平和认识程度,为正确把握西藏喷流型及其它类型矿产资源的战略地位奠定了良好的基础。在此基础上,通过对甲马、沙拉岗矿区的矿床学研究,笔者认为它们都受“盆、相、位”的严格控制,具有喷流沉积的一般特征,属sedex型矿床的范畴。但二者之间却又存在元素组分、矿物成分、结构构造等方面的明显差异。产生这种差异的根本原因在于其形成的大地构造背景和盆地性质不同。

Abstract:

The hydrothermal sedimentation, diagenesis and mineralization may occur in various tectonic settings such as spreading zones, mid-oceanic ridges, trenches, island arcs, back-arc basins, continental rifts and intracontinental fault zones, especially in pericontinental aulacogens and deep swales on carbonate platforms. The Jiama polymetallic deposit and Shalagang antimony deposit have been addressed herein as two good examples. They are all assigned to the sedex deposits and the orebodies commonly appear as stratified and stratoid forms along the stratigraphic horizons. The formation and evolution,sedimentation, diagenesis and mineralization of the basins in which these deposits are hosted tend to be controlled directly or indirectly by the tectonism in south-central Xizang. The comparative study of the two deposits shows that the Jiama polymetallic deposit is located in the inter-arc shallow-marine basin on the active continental margins, whereas the Shalagang antimony deposit lies in the low divide deep-marine basin on the passive continental margins. The differences in tectonic settings are responsible for those in host rocks, elemental components, mineral compositions, types, textures and structures of ores.