摘要
四川龙门山地区石炭系总长沟组底部发育一层鲕状赤铁矿,其内的铁质鲕粒由各种不同类型的核心和同心纹层构成。鲕粒核心主要有3种:由纯赤铁矿颗粒构成的鲕粒核心、由破碎鲕构成的鲕粒核心、由夹有石英颗粒的赤铁矿构成的鲕粒核心。鲕粒同心纹层由赤铁矿及高岭石组成,存在着明显的颜色、成分差别。纹层颜色有暗黑色、铁红色及亮白色,与之相对应,Fe2O3含量分别为39.472%～58.200%、12.988%～24.275%及3.617%～9.230%。三者交替出现,构成鲕粒圈层。通过对鲕状赤铁矿的成分、结构及其他相关特征分析,推测其形成于后砂坝环境。汤靶沟阶晚期存在一次规模较大的古暴露及古岩溶事件,其间风化剥蚀形成的铁铝质风化壳为鲕状赤铁矿提供了物质基础。
A layer of oolitic hematite deposit occurs at the bottom of the Carboniferous Zongchanggou Formation in Longmenshan, Sichuan Province. The ferruginous oolith within it consists of various nuclei and concentric lamellar shells. The oolith nuclei are mainly comprised of hematite intraclast, fragmentized oolith shells or hematite that contains terrigenous quartz sand. The obvious differences of colors and components exist between the oolith lamellar shells composed of hematite and those composed of kaolinite. The lamellar shells can be divided in color into dark black, ferruginous red and white, with the corresponding Fe203 content of the lamellar shells being 39. 472% 58.200%, 12. 988%-24. 275% and 3. 617% -9. 230% respectively. An analysis of components, texture and relative characteristics of oolitic hematite enables us to make an estimation. It is held that the oolitic iron was formed in a semi-closed or closed barrier-lagoon environment. The iron and aluminum weathering crust formed in late Yanguan stage provided the material foundation for the generation of oolitic hematite.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2009年第1期51-57,共7页
Acta Petrologica et Mineralogica
基金
国家自然科学基金资助项目(49802002
40372057)
中国石油化工股份有限公司海相油气勘探前瞻性项目(G0800-06-ZS-319)
关键词
龙门山
鲕状赤铁矿
结构
古环境
Longmenshan
oolitic hematite
texture
paleoenvironment
