贵州习水地区早二叠世古地理和古地貌及其对锂资源的控制作用^*

Early Permian palaeogeography and palaeogeomorphology and their control on lithium mineral resources in Xishui area,Guizhou Province, China

摘要

贵州习水地区发育下二叠统大竹园组铝质沉积物,具有碎屑状、砾屑状、包粒状和泥状结构,岩石类型与锂的富集程度具有明显的相关性。然而,目前对于该地区早二叠世的沉积古地理及古地貌缺乏较为详细和系统的研究,锂的富集与古地理和古地貌的相互关系尚不明确。这也在一定程度上限制了该地区及其邻区下二叠统锂资源的找矿和勘查工作。在野外地质调查、浅表探矿工程和钻孔编录、系统取样的基础上,通过对大竹园组的岩性组合对比、沉积特征分析、地球化学数据及地层厚度统计等,划分了贵州习水地区早二叠世沉积微相,并编制了该时期的古地理和古地貌图,综合分析和探讨了古地理及古地貌对锂资源的控制作用。贵州习水地区在早二叠世位于近岸平原和黔北平原的交汇区域,古盐度分别表现为半咸水和淡水。沉积微相可划分为浅湖、高地、高地边缘、洼地边缘和洼地,古地貌整体呈现南西高、北东低;锂资源主要形成于洼地边缘,含锂岩石以碎屑状铝土岩为主;高地边缘中锂的富集程度相对较低,含锂岩石为包粒状、砾屑状铝土岩、铝土质泥岩,而洼地和浅湖的泥岩和铝土质泥岩中未发现锂的富集。综合分析认为,贵州习水地区锂的富集程度与淋滤作用相关,受古地理和古地貌控制明显。

Abstract

The aluminum-bearing sediments with clastic,gravelly,pelletized and muddy structures of the Lower Permian Dazhuyuan Formation are developed in Xishui area,Guizhou Province. These is an obvious correlation between the rock types and lithium enrichment degree. However,detailed and systematic studies for the Early Permian palaeogeography and palaeogeomorphology in this area are lacking. In addition,the relationship between lithium enrichment and palaeogeography and palaeogeomorphology remains unclear. This knowledge has hindered the prospecting and exploration of Lower Permian lithium resources in this area and its adjacent areas. Base on field geology,prospecting projects,stratigraphic correlation,sedimentary characteristics,geochemical data,etc.,sedimentary microfacies have been recognized,and the Early Permian palaeogeography and palaeogeomorphology maps have been compiled. We comprehensively analyzed and discussed the influence of palaeogeography and geomorphology on lithium mineral resources. The Xishui area of Guizhou Province was located in the confluence area of the coastal plain and the north Guizhou Plain in the Early Permian,and the paleo-salinity was brackish water and fresh water respectively. The sedimentary microfacies can be divided into shallow lake,highland,highland margin,depression margin and depression,and the palaeogeomorphology is characterized by high in southwest and low in northeast. Lithium mineral resources are mainly formed in the depression margin,and the lithium-bearing rocks are mainly clastic bauxite. The enrichment degree of lithium in the highland margin is relatively low,and the lithium-bearing rocks are pelletized bauxite and aluminum-bearing mudstone. However,mudstone and aluminum-bearing mudstone in depression and shallow lake have few lithium contents. The comprehensive analysis shows that the enrichment degree of lithium in the Xishui,Guizhou is related to leaching and is obviously controlled by palaeogeography and palaeogeomorphology.

关键词

锂资源 / 古地理 / 古地貌 / 早二叠世 / 大竹园组 / 贵州

Key words

lithium mineral resources / palaeogeography / palaeogeomorphology / Early Permian / Dazhuyuan Formation / Guizhou Province

基金资助

*贵州新一轮找矿突破战略行动项目: 贵州1︰50000良村幅、温水幅、桑木幅、官店幅矿产地质调查(编号: 黔自然资函[2023]119号-1)资助