發(fā)布時間：2019-02-14 17:45

【摘要】：本文對四川省若爾蓋縣北部-甘肅省迭部縣中-下志留統(tǒng)[蘭多維列統(tǒng)(Llandovery)-溫洛克統(tǒng)(Wenlock)]富有機碳硅質(zhì)巖進行了無機化學(xué)研究,目的是探討其成因及形成環(huán)境,并建立研究區(qū)硅質(zhì)巖形成及相關(guān)元素富集模式。主要對1個鉆孔、2個剖面共28件硅質(zhì)巖的巖相學(xué)、掃描電鏡、主量、微量、稀土元素、有機碳及Si、O穩(wěn)定同位素特征進行了研究。(1)巖相學(xué)、掃描電鏡分析,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‰、同位素對成巖溫度的反演,顯示硅質(zhì)巖為熱水沉積成因,并伴有生物作用(Si、O穩(wěn)定同位素顯示),益哇硅質(zhì)巖形成時陸源物質(zhì)供給適量,導(dǎo)致與碳酸鹽相關(guān)生物繁盛,少量樣品受陸源物質(zhì)影響顯著。(2)巖相學(xué)、掃描電鏡分析,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、有機碳(TOC)-微量元素二元圖解,顯示研究區(qū)硅質(zhì)巖形成于大陸邊緣的熱水噴流導(dǎo)致海底局部水動力較強的缺氧環(huán)境[特別是δCe、(La/Ce)N、稀土配分模式],部分硅質(zhì)巖由于富集熱液元素導(dǎo)致其具有洋脊、大洋盆地硅質(zhì)巖的特征。結(jié)合前人研究成果,認為研究區(qū)硅質(zhì)巖形成于揚子板塊北緣(古商丹洋南緣)熱水噴流系統(tǒng)發(fā)育(導(dǎo)致海底水動能較強的)、缺氧狀態(tài)的陸緣拉張裂陷環(huán)境,這種環(huán)境有利于U、V、Mo、Cu、Ni等變價元素的富集,揚子板塊北緣早古生代(寒武紀-志留紀)黑色頁巖系產(chǎn)自擴張的大陸邊緣缺氧-還原環(huán)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，

本文編號：2422447