Southeast Guizhou is one of the important metal mineralization regions of Guizhou Province.  The dynamic background and metallogenic mechanism of this region has been hot scientific topics for geologists.  In recent years, the researchers of State Key Laboratory of Ore Deposit Geochemistry (SKLODG), Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) has collaborated with the 102 Geological Team, Guizhou Bureau of Exploration and Development of Geology and Mineral Resources on investigating the ore-forming regularities and prospect of Pingzheng- Zaibian- Jiabang- Daping town of Congjiang City in southeast Guizhou Province.

According to the results of the systemic geological-tectonic-magmatic research, combining with the previous remote-sensing image and information, they predicted the possibility of buried intrusive in this region.  The 102 Geological Team decided to verify by drilling. Finally, the buried granite porphyry was found at about 500m under the earth’s surface, and it is still successive to 800m under the earth’s surface．　

Quartz, feldspar and micaphenol-crystals   4×, crossed nicols	Photo of drill core  Buried granite porphyry

(Image by IGCAS)

The preliminary results show that the buried granite porphyry has a typical porphyry texture.  The phenol-crystals contain quartz, feldspar and mica mainly.  Quartz phenol-crystal is gray, mostly with granular size of 2mm×3mm, usually feldspar with granular size of 2mm×10mm, and exceptionally with granular size of 2cm×5cm.  Matrix mineral mainly includes quartz and feldspar, and a small amount of biotite and accessory minerals.  Analysis of major elements shows that SiO2 of rocks is higher than 70wt% and Na2O+K2O are up to 8.90wt%.  The total REE contents of samples rang from 54.8×10-6 to 316×10-6 and chondrite normalized REE patterns show that LREE is enriched and Eu is obvious negative anomaly.  The Co and W content of samples are unusually high with average of 280×10-6 and 850×10-6, respectively.  The fine grain cobaltite was also found in the rocks.  More detailed results have been published in Acta Mineralogica Sinica(2011, 31(1): P160).

The new discovery of the buried granite porphyry in southeast Guizhou province is valuable for the study of magmatic activity, tectonic evolution, and metallogenic mechanism and dynamic background, which is also important for metallogenic prospect.

(provided by ZHOU Jiaxi at SKLODG)