| As Shapinggou large molybdenum deposit was found in Jinzhai County, the relationship between Mesozoic intermediate-acidic magamtic rocks and mineralization in the eastern part of north Huaiyang tectonic belt have become the key point of ore prospecting. Methods as whole rock geochemical analysis, LA-ICP-MS zircon isotope dating and molybdenite Re-Os dating are carried out in this papper, in order to study on the petrologic features of Xianghongdian alkalic complex and and geological characteristics and genesis of Fangjiawa molybdenum deposit. Then concluding their ore-forming regulations, to provide scientific theoretical basis of exploration in this region.Xianghongdian volcanic rocks are composed of pseudoleucite phonolite, trachy tufflava and trachy-pseudoleucite phonolite volcanic breccias. The alkaline intrusive rocks are composed of syenite, alkali-syenite and nepheline syenite, which can be classified as three stages:first stage nepheline syenite (130-136Ma), second stage syenite and dikes (125-130Ma), and third stage alkali-syenite (122-125 Ma).The volcanic and alkaline intrusive rocks have similar geochemical characteristics, almost are alkaline-parlkaline rocks of rich in alkali, high potassium and poor titanium. All the rocks have higher total REE contents, and are rich in LILE such as K, Rb, U, Nd, and depletion of HFSE such as Nb, Ta, P, Ti, which indicate that they are products of the same source, and undergo medium evolution.Fangjiawa deposit is a pohyry molybdenum deposit and its mineragenetic epoch is 123.6Ma, which belongs to the late Yanshanian stge in Dabie mountain molybdenum metallogenic belt. Ore-forming material is from syenite porphyry dikes, and the ore-forming fluid have characteristics of low temperature and low salt. The intersections of NWW-and NE-trending faults can be appropriate hydrothermal channels and spaces of ore-bodies. Above all, searching for intermediate-acidic small rock body is a important direction of molybdenum prospecting. |
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