XiaoChi LIU

China University of Geosciences

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The rare-metal mineralogical study on the Kuqu Li-Be-rich granitic pegmatite from the eastern Himalaya

Acta Petrologica Sinica (2024)

Lei Xie R. C. Wang Ennong Tian Xiangyuan Tao Wei Zhou

在喜马拉雅造山带已发现普士拉、热曲、吉隆、洛扎等多个岩体中花岗岩-伟晶岩与锂铍等稀有金属成矿作用相关,并有大规模的锂辉石伟晶岩(含细晶岩)产出。喜马拉雅东部的库曲岩体也发现了锂辉石伟晶岩出露,主要侵入到主体白云母花岗岩中。本次研究对库曲岩体中不同类型的花岗质伟晶岩进行了详细的岩相学、矿物学和年代学的研究。根据不同矿物组合和产出位置,将库曲伟晶岩分为四类:广泛分布的伟晶岩I,主要包含长石-石英-白云母;岩体西部桑玉村出露伟晶岩II(包含钠长石-石英-白云母带和细粒钠长石带)和伟晶岩III(锂辉石-钠长石-石英带);岩体东部出露细晶岩脉。库曲伟晶岩都含不同体积百分比的石榴石和电气石,以及典型的稀有金属矿物如绿柱石、铌铁矿族矿物和少量锡石。独居石和铌铁矿族矿物的U(-Th)-Pb同位素年代学结果显示库曲伟晶岩主要形成于~25Ma,还存在稍晚一期的岩浆活动,细晶岩形成于~14Ma。同时代的伟晶岩I、II和III全岩成分呈现出明显的变化趋势,K₂O/Na₂O、Zr/Hf和Nb/Ta比值、REE总量和Eu/Eu^*呈降低趋势,而稀有金属(Li、Be、Nb、Ta、Rb和Cs)含量逐渐增加。矿物的成分变化趋势更明显,从伟晶岩I到III中白云母的K/Rb比值和MgO含量明显降低,电气石向更富集Li、石榴子石和铌铁矿族矿物向更富集Mn(在伟晶岩III中分别接近锰铝榴石和铌/钽锰矿端元组分)、绿柱石向更富集Li-Cs的方向变化。伟晶岩III中锡石含量相对增加,常与锂辉石共生。细晶岩脉的矿物学特征介于伟晶岩I和II之间。综合上述研究显示库曲伟晶岩是花岗质岩浆分异演化的最终产物,矿物是伟晶岩形成过程和分异程度的有效指示剂,库曲的稀有金属成矿作用显示出Be、Be-Nb-Ta(-Sn)、Li-Be-Nb-Ta-Sn(岩体最边缘)矿化的变化趋势。锂辉石是库曲伟晶岩中主要的原生锂矿物,次生的锂辉石和石英后成合晶可能是在富锂流体中形成的,而不是透锂长石降温过程中形成的,这与库曲伟晶岩侵入到白云母花岗岩的产状相符。

Pegmatite

10.18654/1000-0569/2024.02.03

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Petrogenesis of the highly fractionated granites and their mineralizations in Nanling Range, South China

Acta Petrologica Sinica (2023)

FuYuan WU ChunLi GUO Fangyang Hu XiaoChi LIU JunXing ZHAO

南岭是我国花岗岩研究程度最高的地区。特别是由于这一地区花岗岩与钨、锡、铌、钽、锆、铪、铜、钼、铅、锌、银、铋、锑、铀、锂、铍、稀土等金属成矿作用关系密切而受到国内外学术界关注。一般认为，南岭花岗岩及相关的成矿作用与花岗岩浆的高度结晶分异作用有关，但高分异作用发生的原因却并不明确。本文通过详细梳理南岭中生代燕山早期花岗岩的特征提出，这些花岗岩的结晶分异作用表现为岩浆房内晶粥体和残留岩浆的长期不断分凝。区内大面积的粗粒似斑状花岗岩为岩浆房早期结晶的堆晶体（主体），而晚期细粒花岗岩则为残留的高硅熔体（补体）。岩浆房发生充分结晶分异作用受控于两个因素：其一是岩浆房自身在演化过程中不断受到来自深部热的补给，使岩浆房内富含金属元素的残留熔体不断发生抽离，并向上运移。花岗岩体顶端的伟晶岩壳是保证抽离的熔体在近封闭环境下不断发生分异的另一个重要因素。这些特征使得南岭花岗岩的分异机制明显有别于喜马拉雅淡色花岗岩，后者以沿大型拆离断层就位并发生分异结晶为主要机制，两者可分别归类为热驱动分异和构造驱动分异类型，构成高分异花岗岩发生的两大重要机制。未来应结合锂资源的国家重大战略需求，对南岭地区高分异花岗岩，特别是晚期钨锡铌钽成矿花岗岩展开全面检查与评价，着重研究铁锂云母花岗岩及云英岩的岩石序列、矿物演变、金属元素富集和岩浆储存机制等，使南岭花岗岩与成矿作用研究再上新台阶。

Petrogenesis

10.18654/1000-0569/2023.01.01

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Citations (64)

Zircon U-Pb age and Hf isotope composition of a quartz vein in ultrahigh-pressure eclogite from the western Dabie orogen

Chinese Science Bulletin (Chinese Version) (2009)

Hujun Gong SaiHong YANG Min Peng XiaoChi LIU Wen-Fang Jiao

In this paper, we report U-Pb age and Hf isotope composition of hydrothermal zircons from a quartz vein within an UHP eclogite outcrop from the Hong’an area, western Dabie orogen. These data are used to decipher the age, formation conditions and source of fluid flow during the exhumation of UHP rock. Zircons from the vein have perfect euhedral shape, oscillatory zoning or weak zoning, and very low Th/U ratios (0.03―0.07), indicating that they precipitated from the aqueous fluid responsible for the vein formation. The weighted mean 206Pb/238U age of 224.7 ± 1.3 Ma of these zircons is taken as the best estimated age of the quartz vein formation, and records aqueous fluid flow during the early exhumation stage of the UHP rocks. The zircons in the quartz vein show low Lu/Hf ratios and have similar Hf compositions to those in the host eclogite, indicating an internal source and small-scale fluid transport for veining. Therefore, the Hf isotope composition of hydrothermal zircon from quartz vein can constrain on the nature, forming condition, and origin of high-pressure metamorphic fluids.

10.1360/972008-1676

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Citations (1)