Jinduicheng Molybdenum Mine Identification Of Two Types Of Porphyry

AbstractLocated in huaxian, shaanxi province, Jinduicheng porphyry Mo deposit is one of the super-large Mo deposits. It is situated within Henan-shaanxi fault uplift at the south margin of north China plate. The basic Ew-trending regional tectonic line is overlapped by the NW-trending structure, this constitutes the overall tectonic frame. Many researchers have done much work on the Jinduicheng granite porphyry, Jinduicheng granite porphyry is completely potassic altered and the alteration is common, so they regarded the potassic-altered granite porphyry as the primary rock. But We find the primary rock trapped in the potassic-altered rock in the field.Jinduicheng granite porphyry is intimately connected with the Mo deposits, Ludugou-lujiagou granite porphyry near Jinduicheng deposit didn't form Mo deposit and it is studied less. We compare the environments of ore-bearing and non-ore-bearing granite porphyries and discuss the character of the Jinduicheng primary rock.Geological and geochemical studies shows Jinduicheng potassic-altered rock and its primary rock, Jinduicheng and ludugou granite porphyry are different in many aspects respectively. The conclusions are in the following.The character of the Jinduicheng primary rock: (1) primary rock is trapped in the potassic-altered rock and has a gradual contact with the potassic-altered rock. It's grey and characterised of more plagioclase, biotite and less muscovite. It's more basic than the altered rock. Potassic alteration is slight in them. (2) The contents of TiO2,Al2O3,FeO,Fe2O3,MgO,Na2O,P2O5 are high and SiO2,K2O are low in primary rock. (3) The values of Rb/Sr and the contents of all kind of ore-forming elements are low in primary rock. These show the post-magmatic flulds had less influence on it . (4) The similarities between the REE signatures of them show that they are hardly different in REE aspect.The difference between the Jinduicheng and ludugou granite porphyry is showed in the following: (1) In geology aspect. Both of them extend in the direction of NW330°, but the former is a larger stock, the latter is a smaller vein. As for the former, the primary rock is grey and altered rock is red. The latter is sage green. From the outer to the center, They both change from fine to coarse, and the change is more obvious in the Jinduicheng granite porphyry. There are lots of veins which cut across each other in the former and no veins except fissures in the latter. (2) The Jinduicheng granite porphyry is characterised of enrichment of SiO2,Na2O, depletion of Al2O3,TiO2,MgO,Fe2O3,FeO,K2O, and lower value of M/F. These facts show its acidity is higher. (3) The former is characterised of high contents of Rb,Pb,W,Sn,Mo,Nb,Tb,U,Th and volatile, High contents of Ba,Cu,Zn,Sr exist in the latter. The contents of the trace element extend a wide range in the former and the contents are stable in the latter. It showed the effect of magmatic fluid during the post-magmatism. High content of Cu,Zn,Ba,Sr show ludugou rock is more basic than Jinduicheng. It is consitent with the analyses of major element. (4) REE patterns of whole rock samples from the three rocks (include laoniushan granite) show a relatively steep right-inclined curve and are basically the same. Both have a low values of δEu, these show both of them are derived from the laoniushan granite. Contrast with ludugou, Jinduicheng granite porphyry is characterised of enrichement of LREE and depletion of Eu is serious. Values of δCe show that they are formed in the different environments. Jinduicheng lies in a more disoxidation enviorment. These facts show Jinduicheng lies in a extensional and crushing tectonic environments . At the cross of the Jinduicheng crushing belt and huanglongpu anticline, where maybe exsit extension and twisting stress at the early stage of the yanmen'au fault activity. These enviorments benefit to the concentration and convection of the ore-bearing fluid.As was stated above,we can reach the conduision that: (1)The primary rock of Jinduichen...