湘南地区骑田岭与香花岭岩体的成矿特征对比

Metallogenic characteristics comparison between Qitianling and Xianghualing intrusion in South Hunan

湘南地区是典型的稀有-有色多金属成矿区,成矿作用与广泛发育的燕山早期花岗质岩浆活动密切相关。以骑田岭和香花岭两个典型成矿岩体为研究对象,对比总结了其岩石学、地球化学、成矿学等方面的特征。骑田岭岩性主要为黑云母二长花岗岩,香花岭则以锂白云母花岗岩、铁锂云母花岗岩等为主;骑田岭花岗岩具有高硅碱、弱过铝质-过铝质的特点,属于钙碱性系列,而香花岭花岗岩较骑田岭更富硅碱,分异程度更高,且高度富集挥发分氟,是高酸富碱氟、高度分异的碱性-过碱性花岗岩;高分异的香花岭岩体发育钨、锡、铌、钽等有色-稀有金属矿床,而同时期的骑田岭岩体仅形成钨、锡矿床。造成这种差异性的原因:从含矿性角度,骑田岭花岗岩中稀有金属含量远不如香花岭岩体;香花岭花岗岩的高分异演化有利于稀有金属和挥发分的逐步富集成矿;骑田岭岩基已遭受高度风化剥蚀作用也可能是原因之一。综合骑田岭岩体的地球化学成矿图解推断,岩体西北部是有利的成矿部位,结合香花岭小岩体的成矿,认为尽管在受风化剥蚀影响较大的岩体西北部找到矿化并非易事,但若附近有出露或隐伏的小岩体,将会是有利的稀有-有色金属矿化部位。

Southern Hunan is a typical non-ferous and rare metal polymetallic metallogenic area in which mineralization is closely related to well-developed granitic magmatism of Early Yanshanperiod. This paper compares different characteristics of petrology,geochemistry,genesis and mineralization between Qitianling and Xianghualing granitoids. It is found that the Qitianling biotite adamellite is weakly peraluminous to peraluminous with high content of silicon,high differentiation,and thus belong to calc-alkaline series,while the granitoids in Xianghualing area are mainly Li-muscovite and zinnwaldite granites,higher contents of silicon and K_2O ＋ Na_2O than Qitianling granitoids. Besides,the granites of Xianghualing small intrusion are weakly peraluminous with high content of fluoride,with well-developed magmatic fractionation and belong to alkaline to peralkaline series.In terms of the mineralization,there are many W,Sn,Nb,Ta deposits in related to small intrusions in Xianghualing area,while only tungsten and tin deposits exist in Qitianling area. We proposed some reasons for this phenomenon. Firstly,the content of rare metal elements in Qitianling granites is lower than that in Xianghualing granites. Secondly,well-developed magmatic fractionation and magmatic-hydrothermal evolution are responsible for high-degree enrichment of rare-metalelements,base metal elements,volatiles in the rocks and further mineralization. Thirdly,the Qitianling batholith experienced strong weathering and denudation. However,the geochemical diagram of mineralization indicates that the northwest side of Qitianling batholithis is favorable for polymetallic mineralization especially when a small intrusion as Xianghualing pluton exists in that place.