| Pianyanzi gold deposit is a rare kind of sellaite type gold deposit in the world,which is large-scale,early researched and exploited in Kangding gold field.Since the exploitation of the deposit, there are no discussions about deep part of this mine deposit that has been mentioned. This article selects this deposit as the research object, focuses on the law of vertical zoning of the deposit to explore genesis,provides a reference for predictive deep prospecting.The main contents of this paper include: regional geological background,regional characteristics of magmatic rocks, geological characteristics of the deposit,geochemical characteristics of the deposit,and element vertical zoning law,etc.Through the research above, the following results be achieved:Deposit locate in the composite parts of two major structure of north-south and north-west.There are stratums like Presinian Kangding Group, Upper Sinian Dengying Formation, Silurian, Devonian and Upper Triassic- Lower Jurassic Hanfengya Group that exposed in this district. Orebodies were significantly controled by geologic layers and faults, outputed in rich-algae dolomites in the middle Dengying Group as complex veins, mainly located in the intersection of two secondary faults of NNE-trending and NNW-trending in the west of major fracture.Range of wall-rock alteration of the deposits spread range broadly consistent with the orebody. With weak alteration and simple type, they all belong to the low-temperature hydrothermal alteration. Most of them are linear alterations, pyrite and silicification closely related to gold mineralization. Structures and compositions of the ore deposit are complicated, the vast majority of mineral are metallic minerals, then are non-metallic minerals.Almost all the gold orebodies of Pianyanzi gold deposit extend near the north-south direction. The types of gold-bearing geologic bodies contain the auriferous quartz sulfide veins that interspersed in the dolomite, and the ore-bearing dolomite that associated with diabase. The age of zircon 206Pb/238 U of the mafic diabase ranges 397.6Ma to 496.7Ma, weighted average of 434.5 ± 5.1Ma. That age may be crystallization age of the diabase of Pianyanzi gold deposit. Derived through the quartz ESR test we get that last activity age of the quartz is substantially between16.2Ma to 16.5Ma, the average age was 16.4Ma. Big age difference between the two,indicating that the formation of diabase and deposits are not directly linked, but the basic dikes and gold is closely related in space.Pyrite sulfur isotope analysis of quartz veins in Pianyanzi gold deposit shows that, ?34S has characteristics such as concentrated distribution and a higher degree ofuniformity, and the isotopic composition in line with magma sulfur or sulfur mantle characteristics. It can be said that they may come from deep magma and gold mineralization is closely related to magmatic hydrothermal activity.Pianyanzi gold deposit have obvious vertical zonation. From a macro point of view, vertical zoning rules of deposits of mineral assemblages are: the mineral assemblages in shallow part are pyrite with quartz combinations; in the middle are chalcocite and pyrite with quartz and ankerite combinations; in deep part there are galena or sphalerite with tetrahedrite and quartz and pyrite combinations. The contents of elements such as Th, Ce, Sr, Zr, Ti show depleted. The contents of great LILE Rb show relatively enrich, the contents of Ba show relatively depleted. The contents of trace elements about Ba of the quartzs in shallow part are significantly higher than in the deep part, and the contents of most other trace elements are exactly the opposite. The quartzs produced in shallow part are relatively purer. Fractionations of LREE and HREE are the same no matter in shallow part or in deep part. Quartzs in shallow part show negative Ce anomalies, positive and negative Eu anomalies.Quartzs in deep part show little or slightly negative anomalies in Ce and Eu. |
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