摘要
新疆大红柳滩伟晶岩型锂矿床近年来找矿取得了新进展。我们在该地区典型锂矿脉(90-1号)首次鉴定出磷铁锂矿,其在伟晶岩中呈树枝状、团簇状集合体分布岩脉的边缘带和中部。边缘带尤为富集磷铁锂矿,含量可达10%~15%。本文系统地开展了磷铁锂矿的岩相学和矿物学研究。利用电子探针和激光剥蚀等离子质谱测定了脉体边缘带和中间粗粒锂辉石-白云母-石英带磷铁锂矿的主微量元素含量。结果表明,磷铁锂矿除含有主要元素P、Fe、Mn及Li外,还含有较高的Mg、Ca和Zn,几乎不含高场强元素、稀土元素。综合电子探针和LA-ICP-MS分析结果,认为伟晶岩脉中部分磷铁锂矿已被氧化,成分向铁磷锂锰矿过渡。从脉体的边缘带往中间带,磷铁锂矿中Mg和Zn平均含量下降,而Mn/(Mn+Fe)比值由0.388升至0.409,显示逐渐富Mn特点,与前人关于花岗伟晶岩熔体演化过程中Fe-Mn的分离趋势一致,也与该伟晶岩脉中铌钽铁矿早期演化阶段Mn/(Mn+Fe)比值变化趋势相同;磷铁锂矿被晚期氟磷灰石部分交代,反映伟晶岩演化至热液阶段F、Ca活度增加。表明该矿物可以很好的记录伟晶岩岩浆及热液阶段的演化。
This contribution presents a detailed petrographic and mineralogical study of triphylite from the wall zone and coarse-grained spodumene-muscovite-quartz zone(intermediate zone) of No. 90-1 spodumene pegmatite at Dahongliutan, Xinjiang. Triphylite occurs as dendritic or rounded aggregates in the pegmatite. Electron probe micro-analyzer(EPMA) and laser ablation-inductively coupled plasma-mass spectrometer(LA-ICP-MS) were used to determine the concentrations of major and trace elements in triphylite. Our results show that, besides major elements P, Fe, Mn, and Li, the triphylite contains subordinate Mg, Ca, and Zn. Moreover, HFSE and REE concentrations of the triphylite are extremely low. Integrating the EPMA and LA-ICP-MS data, our study indicates that the triphylite has been partially oxidized and that its composition has evolved towards ferrisicklerite. From the wall zone towards the intermediate zone, the triphylite shows decreased Mg and Zn contents but becomes relatively Mn-enriched as the Mn/(Mn+Fe) ratios of triphylite increase from 0.388 to 0.409. Such a compositional evolutionary trend is consistent with the typical Mn-Fe fractionation trend in many pegmatites according to the literature. Similarly, the columbite-group minerals in the same pegmatite show increasing Mn/(Mn+Fe) ratios at early stages. In addition, the triphylite is partially replaced by fluorapatite, which suggests that the activities of Ca and F increased at the late hydrothermal stage. This suggests that triphylite has potential to document magmatic and hydrothermal evolution of pegmatites.
作者
凤永刚
王艺茜
张泽
梁婷
周义
高景刚
腾家欣
FENG Yonggang;WANG Yiqian;ZHANG Ze;LIANG Ting;ZHOU Yi;GAO Jinggang;TENG Jiaxin(School of Earth Science and Resources,Chang’an University,Xi’an,China,710054;Laboratory of Mineralization and Dynamics,Chang’an University,Xi’an,China,710054;Xi’an Center of China Geological Survey)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2019年第6期1405-1421,共17页
Acta Geologica Sinica
基金
国家重点研发计划项目“深地资源勘查开采”专项“锂能源金属矿产基地深部探测技术示范”项目所属课题“我国锂能源金属成矿规律、靶区优选及异常查证”(课题编号2017YFC0602701)
中国地质调查局“西昆仑铁铅锌资源基地调查与勘查示范”项目(编号DD20160004-8-3)的联合资助
