We report the new discoveries of ore-hearing quartz albite porphyry and of some peculiar geological phenomenon, including intrusions of quartz K-feldspar porphyries into karst caves and biotite K-feldspar porphyries into poorly consolidated lacustrine sedimentary rocks and formation of some rare structures and textures, such as coexistence of microcrystalline and vitreous-cryptocrystalline groundmass and formation of new type peperites, in the Beiya gold mineral district, western Yunnan. We also show Ar-39/Ar-40 ages of the porphyries in Beiya which indicate that the quartz albite porphyry intruded in early Tertiary with an age of 65.56Ma, while the quartz K-feldspar porphyries formed between 25 and 33Ma, and the biotite K-feldspar porphyries have intrusive ages of 3.78 Ma to 3.65 Ma. All the quartz albite porphyry, quartz K-feldspar porphyries and biotite K-feldspar porphyries in the Beiya gold mineral district are alkaline and have some similar geochemistry features, including (K2O + Na2O) > 10%, SiO2 > 67%, Sr >400 x 10(-6), Sr-87/Sr-86 >0.707, LREE rich, REI. distribution pattern similar to that of OIB. Features of REE composition and Nd-Sr-Pb isotope of these alkaline porphyries suggest. that they are most likely to be origin form a mixed source containing compositions of OIB, MORB, normal sedimentary rocks and upper mantle (EMII + PREMA), and we further propose that the alkaline porphyries in the Beiya gold mineral district, similar to other Tertiary alkaline porphyries in western Yunnan, are related to partial melting lie within a shear zone between buried paleo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India to Asia.
