扬子板块北缘早—中志留世硅质岩成因及古沉积环境的地球化学研究
发布时间：2019-02-14 17:45
【摘要】：本文对四川省若尔盖县北部-甘肃省迭部县中-下志留统[兰多维列统(Llandovery)-温洛克统(Wenlock)]富有机碳硅质岩进行了无机化学研究,目的是探讨其成因及形成环境,并建立研究区硅质岩形成及相关元素富集模式。主要对1个钻孔、2个剖面共28件硅质岩的岩相学、扫描电镜、主量、微量、稀土元素、有机碳及Si、O稳定同位素特征进行了研究。(1)岩相学、扫描电镜分析,Fe/Ti、Al/(Al+Fe+Mn)(0.08~0.79)均值0.31、(Fe+Mn)/Ti,(La/Yb)N(0.12~1.41)均值0.54、δEu(0.81~3.36)均值1.55、∑REE(7.59~253.48)均值82.90,Si同位素(-0.2‰~2.1‰)均值0.66‰、O同位素(13.5‰~21.8‰)均值19.53‰、同位素对成岩温度的反演,显示硅质岩为热水沉积成因,并伴有生物作用(Si、O稳定同位素显示),益哇硅质岩形成时陆源物质供给适量,导致与碳酸盐相关生物繁盛,少量样品受陆源物质影响显著。(2)岩相学、扫描电镜分析,MnO_2/TiO_2、Al2O3/(Al2O3+Fe2O3)、Al/(Al+Fe)(0.08~0.80)均值0.33、Th/U、V(28.6×10~(-6)~2261×10~(-6))均值454.42×10~(-6)、Ti/V,δCe(0.65~1.58)均值1.01、(La/Ce)N(0.60~1.314)均值0.97、有机碳(TOC)-微量元素二元图解,显示研究区硅质岩形成于大陆边缘的热水喷流导致海底局部水动力较强的缺氧环境[特别是δCe、(La/Ce)N、稀土配分模式],部分硅质岩由于富集热液元素导致其具有洋脊、大洋盆地硅质岩的特征。结合前人研究成果,认为研究区硅质岩形成于扬子板块北缘(古商丹洋南缘)热水喷流系统发育(导致海底水动能较强的)、缺氧状态的陆缘拉张裂陷环境,这种环境有利于U、V、Mo、Cu、Ni等变价元素的富集,扬子板块北缘早古生代(寒武纪-志留纪)黑色页岩系产自扩张的大陆边缘缺氧-还原环境。
[Abstract]:In this paper, the inorganic chemistry of organocarbon-rich siliceous rocks in the middle and lower Silurian of the northern part of Ruoergai County and Dibu County of Gansu Province [(Wenlock)] of the Ordovician (Llandovery)-Wenlock Series) has been studied in order to discuss its genesis and formation environment. A model for the formation of siliceous rocks and the enrichment of related elements in the study area was established. The characteristics of lithology, scanning electron microscope, principal quantity, trace, rare earth element, organic carbon and Si,O stable isotopes of 28 siliceous rocks in 1 borehole and 2 sections were studied. (1) Petrography, scanning electron microscope analysis, Fe/Ti,. The mean value of Al/ (Al Fe Mn) (was 0.31, (Fe Mn) / Ti, (La/Yb) N (0.121.41) was 0.54, 未 Eu (0.81 ~ 3.36) was 1.55, 鈭，
本文编号：2422447
[Abstract]:In this paper, the inorganic chemistry of organocarbon-rich siliceous rocks in the middle and lower Silurian of the northern part of Ruoergai County and Dibu County of Gansu Province [(Wenlock)] of the Ordovician (Llandovery)-Wenlock Series) has been studied in order to discuss its genesis and formation environment. A model for the formation of siliceous rocks and the enrichment of related elements in the study area was established. The characteristics of lithology, scanning electron microscope, principal quantity, trace, rare earth element, organic carbon and Si,O stable isotopes of 28 siliceous rocks in 1 borehole and 2 sections were studied. (1) Petrography, scanning electron microscope analysis, Fe/Ti,. The mean value of Al/ (Al Fe Mn) (was 0.31, (Fe Mn) / Ti, (La/Yb) N (0.121.41) was 0.54, 未 Eu (0.81 ~ 3.36) was 1.55, 鈭，
本文编号：2422447
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