扬子北缘白田坝组含锂细碎屑岩物源与沉积环境分析
- 收稿日期:
2024-03-07
- 网络出版日期:
2024-07-18
摘要: 扬子陆块北缘二叠纪—侏罗纪多个层位中锂矿化体的发现,对沉积型锂资源调查研究与开发利用意义重大。为查明侏罗系白田坝组含锂细碎屑岩源区母岩性质及构造背景,并初步探讨古环境对锂富集的控制作用,对该组地层典型岩性做了详细的岩石学研究,并针对含锂(富锂)细碎屑岩进行了XRD分析和元素地球化学研究。研究结果:主量元素氧化物判别函数和LaN/YbN-ΣREE、K2O-Rb、La/Th-Hf 图解显示潜在物源区是一个出露中酸性火成岩、沉积岩和变质岩的混合源区;主量元素氧化物判别函数和La-Th、Ti/Zr-La/Sc、La-Th-Sc、Th-Sc-Zr/10、Th-Co-Zr/10图解反映沉积期构造背景为活动陆缘,而源区部分母岩形成于大陆岛弧环境;Ga、Sr/Ba、Sr/Cu、C值、CIA、U/Th、Ni/Co等古环境指标指示含锂细碎屑岩沉积于温暖潮湿气候条件下的弱还原—氧化淡水环境,且A-CN-K和Th/Sc-Zr/Sc图解说明碎屑物在首次沉积时源区母岩已经经历了中等—强烈程度的风化作用。综合研究表明:古盐度和古还原氧化条件对锂富集具一定控制作用,但含锂(富锂)细碎屑岩中黏土矿物的含量才是决定锂能否富集的关键。物源区锂的含量水平对锂富集起主导作用(“源”),沉积环境通过影响黏土矿物的含量来影响地层中锂的含量(“储”)。
Provenance and Paleodepositional Environment of Li-rich Fine-grained Clastic Rocks from Baitianba Formation in the North Margin of Yangtze Block
- Received Date:
2024-03-07
- Available Online:
2024-07-18
Abstract: The discovery of lithium mineralized bodies in multiple layers of the Permian-Jurassic layers in the northern margin of the Yangtze Block is of great significance to the investigation, development and utilization of sedimentary lithium resources. In order to clarify the provenance and tectonic setting of the parent rock in the source area of the lithium-bearing fine clastic rocks of the Jurassic Baitianba Formation, and to discuss the control of the paleo-environment on lithium enrichment, the typical lithology of the strata has been studied in detail, and the XRD and elemental geochemistry studies have been carried out. Results: The main element oxide discriminant function and LaN/YbN-ΣREE, K2O-Rb and La/Th-Hf diagrams show that the potential provenance region is a mixed provenance region of emerging medium-acid igneous rocks, sedimentary rocks and metamorphic rocks. The main element oxide discrimination function and the diagrams of La-Th, Ti/Zr-La/Sc, La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 show that the tectonic background of the sedimentary period was active continental margin, and some parent rocks in the source area were formed in continental island arc environment. Ga, Sr/Ba, Sr/Cu, C value, CIA, U/Th, Ni/Co and other paleoenvironmental indicators indicate that lithium-containing fine clastic rocks were deposited in a weakly reduction-oxidizing freshwater environment in a warm and humid climate. The A-CN-K and Th/ Sc-Zr /Sc diagram show that the parent rock of the source area has undergone moderate to intense weathering when the debris was first deposited. The comprehensive study shows that paleosalinity and paleoreduction-oxidation conditions control the enrichment of lithium to some extent, but the content of clay minerals in lithium-containing fine clastic rocks is the key to determine the enrichment of lithium. The lithium content level in the source area plays a leading role in lithium enrichment (" source "), and the sedimentary environment affects the lithium content in the formation (" storage ") by influencing the content of clay minerals.