摘要
Darling Range位于西澳大利亚地区,红土型铝土矿资源丰富。本文对Darling Range地区红土型铝土矿及相关岩石开展了元素地球化学分析,并对铝土矿中的碎屑锆石和其下伏的花岗岩开展了LA-ICP-MS锆石U-Pb测年,目的是探讨西澳地区红土型铝土矿的成矿作用及其源区。结果表明,西澳地区红土型铝土矿的主量元素以Al2O3、Fe2O3、SiO2和TiO2为主,Al2O3与SiO2呈显著的负相关关系,与TiO2则呈现显著的正相关关系,表明铝土矿的形成过程是一个去Si富Al、Ti的过程。铝土矿微量元素富集Th、U、Nb、Ta、Zr、Hf、Ti,相对亏损Ba、K、Sr、P、Sm;稀土总量较低,为1.36×10^(-6)~65.58×10^(-6),稀土元素球粒陨石标准化分布曲线略微向右倾斜,富集轻稀土。铝土矿碎屑锆石U-Pb年龄分布于1167Ma和1267Ma与2539~2696Ma(16颗)两个年龄段,分析锆石来源前者可能来自Albany-Fraser造山带;后者加权平均年龄为2579±15Ma(MSWD=1.16),与研究区本次获得的太古宙花岗岩加权平均年龄2585±12Ma(MSWD=0.83)在误差范围内一致,表明铝土矿中的锆石除了来自本区太古宙花岗岩,还有少量的锆石来自Albany-Fraser造山带。结合元素地球化学钛率(Al2O3/TiO2)、lgCr-lgNi、微量元素比值、稀土元素配分模式对铝土矿源区进行示踪表明,Darling Range地区的太古宙花岗岩为红土型铝土矿的主要物质来源。
Located in western Australia,Darling Range is rich in laterite-type bauxite resources.In order to understand metallogenesis of the laterite-type bauxite in Darling Range and constrain the source of oreforming materials,this study carried out element geochemistry analysis and LA-ICP-MC dating of detrital zircons from bauxite and underlying granite.The results show that the bauxite in the Darling Range are composed mainly of Al2O3,Fe2O3,SiO2,and TiO2.Al2O3 has a negative relationship with SiO2,but a positive relationship with TiO2.It suggests that bauxite experienced the loss of Si and enrichment of A1 and Ti during the ore-forming process.Geochemical analysis shows that the bauxite is enriched in Th,U,Nb,Ta,Zr,Hf and Ti,and depleted in Ba,K,Sr,P and Sm.The bauxite is characterized by low REE contents from 1.36 × 10^-6 to 65.58× 10^-6,and the chondrite-normalized REE pattern slightly tilts to the right and shows enrichment in LREE.LA-ICP-MC detrital zircon U-Pb ages of the bauxite can be assigned to two groups:1167~1267 Ma (2 zircons) and 2539~2696 Ma (16 zircons).The former younger detrital zircons possibly came from Albany-Fraser orogeny,while the later older detrital zircons have the weighted average ages of 2579±15 Ma (MSWD=1.16),consistent with 2585±12 Ma (MSWD=0.83) of Archean granite,with the difference within the error.This indicates that besides the zircons from Archean granite,minor zircons in the laterite-type bauxite may derive from Albany-Fraser orogeny belt.Using Al2O3/TiO2 ratio,lgCr-lgNi plot,trace element ratios,and REE pattern to trace the source of laterite-type bauxite deposit,it can be concluded that Archean granite is the major source of ore-forming materials for the laterite-type bauxite deposit in the Darling Range of western Australia.
作者
孙朋飞
江思宏
韩宁
SUN Pengfei;JIANG Sihong;HAN Ning(School of Earth Sciences and Resources,China University of Geosciences ,Beij ing ,100083;MLR Key Laboratory of Metallogeney and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing ,100037)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2018年第3期587-603,共17页
Acta Geologica Sinica
基金
国家地质大调查项目(编号1212011120325和121201103000150006)资助的成果.
