發(fā)布時(shí)間：2018-02-07 14:48

  本文關(guān)鍵詞： 硅質(zhì)沉積物 沉積環(huán)境 構(gòu)造背景 中上泥盆統(tǒng) 羅甸 貴州　出處：《地質(zhì)學(xué)報(bào)》2017年09期 　論文類型：期刊論文

【摘要】：黔南羅甸地區(qū)中晚泥盆世廣泛發(fā)育深水相沉積硅質(zhì)巖、灰?guī)r,其建造類型明顯不同于增生型或島弧型硅質(zhì)巖,屬于一種特殊的硅質(zhì)巖建造類型。對羅甸蒙江(中、上泥盆統(tǒng))和過石寨(中泥盆統(tǒng))42件硅質(zhì)巖類樣品進(jìn)行巖石學(xué)、礦物學(xué)以及主量和稀土元素地球化學(xué)研究,結(jié)果表明,中泥盆世硅質(zhì)沉積物Al_2O_3(0.62%~22.1%)、TiO_2(0.01%~0.84%)、Fe_2O_3(0.41%~10.5%)、∑REE(7.87×10~(-6)~319×10~(-6))、Ce/Ce*(0.51~0.96)值整體偏高,而Y/Ho值(26.6~37.0,平均30.8)和(La/Ce)N值(1.06~1.99,平均1.28)相對較低。晚泥盆世硅質(zhì)沉積物的Al_2O_3(2.42%~10.6%)、TiO_2(0.06%~0.43%)、Fe_2O_3(0.62%~2.65%)、∑REE(28.7×10~(-6)~163×10~(-6))、Ce/Ce*(0.45~0.82)值則相對偏低,而Y/Ho值(28.2~36.7,平均34.2)和(La/Ce)N值(1.34~2.34,平均1.82)相對升高。除去SiO_2稀釋作用影響,區(qū)內(nèi)硅質(zhì)沉積物稀土元素含量及來源變化均大,其中上泥盆統(tǒng)硅質(zhì)沉積物中(∑REE+Y)除部分來自陸源碎屑外,更多地從海水中獲取。結(jié)合Al2O_3/TiO_2-Al(Al+Fe+Mn)、Al-Fe-Mn和(∑REE+Y)-SiO_2/Al_2O_3圖解,以及主量和稀土元素地球化學(xué)特征,認(rèn)為羅甸中晚泥盆世硅質(zhì)沉積物為正常海相沉積,從中泥盆世到晚泥盆世,沉積環(huán)境已由較為局限的邊緣裂谷盆地向開闊的邊緣裂谷盆地轉(zhuǎn)化。這對深刻認(rèn)識(shí)水城-紫云-南丹晚古生代裂陷盆地,以及右江盆地在中晚泥盆世的發(fā)展、演化過程均具有重要意義。
[Abstract]:Deep-water sedimentary siliceous rocks and limestone were widely developed in Luodian area of southern Guizhou Province in the late Devonian. Their formation types are obviously different from accretive or island-arc siliceous rocks, and belong to a special type of siliceous rock formation. The petrology, mineralogy, principal quantity and REE geochemistry of 42 siliceous rock samples from the Middle Devonian are studied. The results show that the values of Al2O3O20.62 and TiO20.01 in the siliceous sediment of the Middle Devonian are relatively high, 鈭，

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