摘要
以热液作用为联结点,将斑岩和围岩作为一个整体系统来考虑,对乌奴格吐山特大型斑岩铜-钼矿床热液蚀变矿化过程中REE行为进行了研究,首次发现热液蚀变过程中母岩与围岩REE变化具互补性,铕亏损对斑岩矿化具指示意义。分析了REE的赋存矿物及其在蚀变过程中的变化,推断成矿流体具有贫REE、相对富∑~Y、强烈亏损铕的性质。在中强蚀变带斑岩和围岩基本上是以等比质量参与热液蚀变交代的。稀土元素、流体包裹体和氢、氧同位素研究的结果,证实了热液对流的存在及围岩提供部分矿质的可能性。应用REE地球化学找矿有一定的潜力。
The Wunugetushan porphyry Cu-Mo deposit of Inner Mongolia is a very large one of its kind. The major ore-bearing wall rock is biotite granite (γβ, 187Ma)and the mineralizing parent rock is monzogranitic porphyry (ηγπ, 138Ma, 0.5km^2). The alteration area reaches 10km^2. Alteration can be divided into three zones, i. e. those of quartz-potash feldspathization (Q-Kf, Ⅰ), quartz Sericitization (Q-Ser, Ⅱ) and argilligation I-H, Ⅲ) from the centre outwards. Correspondingly, the mineralization zoning is Mo(Cu)→Cu(Mo)→Pb, Zn, Ag.The unaltered γβ's ΣREE=149.63—157.20ppm and δEu=0.61—0.63; unaltered ηγπ's ΣREE=78—80.15ppm and δEu=1.08—1.12. The obvious Eu-depletion(δEu=0.45—0.59) occurred in both of them after alteration. The more pronounced the Eu-depletion, the better the mineralization, Eu-depletion is of certain significance in indicating mineralization.After alteration ηγπ's ΣREE increases. ΣREE increases 0.64 times in zone Ⅰ and 0.18 times in zone Ⅱ; ηγπ's zone Ⅲ has been eroded. After alteration γβ's ΣREE decreases. REE decreases 0.39, 0.12 and 0.46 times in zones Ⅰ, Ⅱ and Ⅲ respectively. More increase of ηγπ in zone i is in accord with γβ's more decrease in the same zone. ΣREE variation in zone Ⅱ is similar to that in zone Ⅰ, but the range is smaller. There exists complementary nature for REE variation in hydrothermal alte.,ration between porphyry and wall rock. The existence of hydrothermal convection and important metallogenic significance of polyphase alteration overlapping are confirmed by REE, oxygen isotope, Rb/Sr ratio and fluid inclusion studies.REE of wall rock is mainly hosted in accessory minerals, whereas REE of porphyry is chiefly hosted in rock-forming minerals. Mineralogical variation in alteration is in accord with REE variation of rocks. REE occurs respectively as chloride, F^- complex and F^- and CO_3^(2-) complexes in zones Ⅰ, Ⅱ and Ⅲ. The authors infer that the ore fluids should be characterized by ΣREE depletion but relative enrichment in ΣY and strong depletion in Eu. ηγπ and γβ participate in hydrothermal alteration and metasomatism almost in equal mass proportions. Results of the studies indicate that the application REE geochemistry in mineral prospecting has great potential.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1993年第4期323-335,共13页
Acta Geologica Sinica
基金
国家"七.五"重点科技攻关项目 55-03-11-4课题
关键词
稀土族
热液对流
铜-钼矿床
REE behaviour, Wunugetushan Cu-Mo deposit, hydrothermal alteration
