四川攀西地区氟碳铈矿型内生稀土矿床成矿模式

GENETIC MODEL FOR THE BASTNAESITE-TYPE ENDOGENETIC ORE DEPOSITS OF REE IN PANZHIHUAXICHANG REGION, SICHUAN

四川攀西地区氟碳铈矿型内生稀土矿床成矿模式秦震（四川省地质矿产局）１大地杓造背景本类型矿床位于扬子地台西缘康滇地轴中段的西侧，为康滇地轴与甘孜地槽之间的台缘坳陷过渡地带。深部处于龙门山一锦屏山幔坡陡倾转折部位，系陆壳脆弱带。２控矿构造矿床分布乎格受求...

Abstract This type of ore deposits is distributed over the western side of middle sector of kangdian axis in the western margin of Yangtze platform . The ore-control structural system consists of deep fractures as passageway for deep-seated ore fluid and surface subsidiary fractures as host structure.The host rock is an alkali compled consisting of aegirine granite and associated REE-rich dikes such as aegirine-barite pegmatite dike and carbonatite dike which occur as stock or dike without zonation. Abundance of REE in the alkali complex is up to 2900×10-6-4570×10-6.The REE distribution pattern is characterized by intense enrichment in LREE with negative Er anomaly and withhout negative Eu anomaly which suggest REE ore material derived directly from the alkali complex.The ores were formed in the Late Yanshan epoch(80-140Ma),or in the Himalayan epoch(Yun Zhongxin, 1995). Most of the orebodies are confined to the alkali complex as vein, lenticule and stockwork with a great disparity on a scale.REE content in bastnaesite accounts for more than 85 per cent of that in the ore.The ore is readily sorting and smelting with a coarse texture and low damaging elements.The ore-formation resulted from infilling and spontaneous crystallization of late magmatic hydrothermal solution in tectonic fissures without participation of surface material. Therefore, wallrocks of the ore-bearing alkali complexes may be different. Bastnaesite is associated with U-Th-rich minerals such as thorite and betafite, thus, radioactive(γ-ray)anomalies occur in the orefields. Meawhile, La-Ce-Mo-Pb geochemical anomalies and thorites-bastnaesite-barite heavy minerals anomalies occur in the ore field. To sum up, 'four in one'of ruptured zone-aegirine granite-alkali pegmatite dike-carbon-ante dike-radioactive(γ- ray)anomaly is fundamental metallogenic conditions and genetic model for this type of ore deposits.