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Lancang old mines the area in the late eighties of the last century have been exposed to in the borehole veinlets and porphyry skarn belt, but until 2008, for exposing concealed rock engineering few core obtained limited, granite porphyry petrology, geochemistry, geochronology and mineralization Relationship with the slow progress, relevant outcomes scarce. 2007 Alternative Resources Prospecting in Crisis Mines special - Lancang County, Yunnan Lancang Lead Mine succeed exploration project implementation, ZK153101 drilling again exposed to the three sections of granitic porphyry dikes, ZK14824 other boreholes revealed to skarn rock band and molybdenum ore body, in 2009 and in ZK14827, ZK14830, ZK15501 holes exposed to the multistage porphyry dikes, the final hole to expose the main rock. To identify old mines buried porphyry district characteristics, this article from porphyry rock geology, petrology, geochemistry, geochronology and zircon typomorphic characteristics and other aspects of comprehensive study of its genetic type and form of tectonic environment. The area exposed to the concealed porphyry rock and relating molybdenite mineralization, skarn mainly in the east fault F3, F4 fault line -9 144 west between the lines, in general along the F1 fault distribution, elevation appeared roughly 900-1530m, there is a trend from west to east. Petrographic studies show that the area was light gray granite porphyry, gray, porphyritic massive structure, mainly by phenocrysts of orthoclase, quartz, plagioclase and biotite matrix consists of fine equiaxed micro-orthoclase , quartz. Geochemical studies show that older plants are concealed metaluminous granitic porphyry K calc-alkaline granites; trace elements K, La, Hf, Tb relative enrichment, Nb, Ta, P, Ti relative losses, reflecting the orogenic granite and features of the continental crust; REE smaller average 126.56x10-6, (La / Yb) N = 12.01-24.85, moderate LREE enrichment; 87Sr/86Sr of 0.70835-0.71544, average 0.71. SHRIMP U-Pb zircon dating confirmed Lancang old factory buried porphyry emplacement crystallization age of 44.6 ± 1.1Ma, and western Yunnan Himalayan orogeny main collisional phase (65-41 Ma) at the end considerably. The Lancang old mines area molybdenite Re-Os isotopic dating results (43.78 ± 0.78Ma) and granite porphyry SHRIMP U-Pb zircon age of (44.6 ± 1.1Ma) is very similar, both for early Himalayan ( Late Eocene) of the product, and the age of the data in the rock slightly new age, and porphyry hydrothermal mineralization of the overall later diagenetic basic law coincide. Old factory granite porphyry-type zircon group is simple, there are four main types and 20 subtypes. Zircon crystal mainly by {100}, {110} and {101} cylindrical, conical form {211}, {110} in which the cylinder is most developed, cone {] 01} and {211} are more developed, but {101} {211} more than the development, with a low temperature too alkaline environment zircons. Zircon standard type indicates mine porphyry is dominated crust mantle source mixing origin of granite porphyry. Composite granite porphyry geochemistry, zircon and isotopic characteristics typomorphic judgment concealed porphyry old plant should be based on the main crustal remelting, some mantle materials involved mixing genesis granite porphyry. Porphyry district formed in Cenozoic collision orogeny evening among the main collision collision conversion period, in the space produced in the west of the Lancang fracture Late Paleozoic rift zone, the zone is a dynamic environment orogenic environment.
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