The provenance of late Permian karstic bauxite deposits in SW China, constrained by the geochemistry of interbedded clastic rocks, and U–Pb–Hf–O isotopes of detrital zircons
The provenance of late Permian karstic bauxite deposits in SW China, constrained by the geochemistry of interbedded clastic rocks, and U–Pb–Hf–O isotopes of detrital zircons
复制标题
DOI：
10.1016/j.lithos.2017.01.013
复制
发表时间：
2017-05
期刊：
影响因子：
3.5
通讯作者：
Ying-ling Hou;Yuting Zhong;Yigang Xu;B. He
中科院分区：
文献类型：
--
作者：
Ying-ling Hou;Yuting Zhong;Yigang Xu;B. He
岩溶型铝土矿是岩石强烈风化的产物，其物源难以确定。研究了西南晚二叠世岩溶型铝土矿床的层间碎屑岩地球化学特征和碎屑锆石同位素特征，以了解其物源。碎屑岩和铝土矿碎屑锆石U-Pb年龄均在~ 260 Ma处出现峰值。该峰年龄与铝土矿的沉积年龄（259.8±0.4 Ma）和中国西南部峨眉山大火成岩省的侵位年龄误差不大。峰年龄和碎屑岩中丰富的火山石英晶体碎屑表明铝土矿床来源于火山岩。碎屑岩的Al2O3/ tio2值为25 ~ 132，δEu值为0.23 ~ 0.58，REE呈弧形趋势，烃源岩为长英质烃源岩。铝土矿矿石和碎屑岩的εNd(T)值一般在−7.6 ~−3.5之间，140个碎屑锆石中有130个的εHf(T)值在−26.7 ~−0.6之间，δ18O值在+ 5.6‰~ + 10.3‰之间，符合以地壳物源为主的特征。根据中国西南地区二叠系岩浆岩的古地理和分布特征，岩溶型铝土矿可能来源于古特提斯北缘二叠系岩浆弧的长英质火山岩，而不是来自峨眉山大火成岩省。该研究为全球岩溶型铝土矿床的物源研究提供了新的视角，并对极端风化过程中元素的流动性有了新的认识。
The provenance of karstic bauxite deposits is difficult to constrain as such deposits are the products of intensively weathered rocks. We have studied the geochemistry of interbedded clastic rocks and isotopic characteristics of detrital zircons in late Permian karstic bauxite deposits in SW China to understand their provenance. The U–Pb ages of detrital zircons from both clastic rocks and bauxite ores show a peak at ~ 260 Ma. This peak age is within error of the sedimentary age (259.8 ± 0.4 Ma) of the bauxite ores and the age of emplacement of the Emeishan large igneous province in SW China. The peak age, together with abundant fragments of volcanic quartz crystals in the clastic rocks, suggests that the bauxite deposit was derived from volcanic rocks. Further, the clastic rocks yield Al2O3/TiO2values of 25–132 and δEu = 0.23–0.58, showing arc-like REE trends and indicating that the source rocks were felsic. The εNd(T) values of the bauxite ores and clastic rocks typically range from − 7.6 to − 3.5, with 130 out of 140 detrital zircons yielding εHf(T) values of − 26.7 to − 0.6 and δ18O values of + 5.6‰ to + 10.3‰, consistent with a dominantly crustal provenance. Based on the paleogeography and distribution of Permian magmatic rocks in SW China, it is likely that the karstic bauxite deposits were derived from the felsic volcanic rocks of a Permian magmatic arc at the northern margin of the Paleo-Tethys, rather than from the Emeishan large igneous province. This study provides a new perspective on the provenance of karstic bauxite deposits worldwide and yields insights into element mobility during extreme weathering.