Where Are Porphyry Copper Deposits Found
Porphyry copper deposits are mainly distributed in Cenozoic, accounting for about 59.5%, followed by Mesozoic, accounting for about 35%. The super-large porphyry copper deposits before Mesozoic are limited to the Paleozoic orogenic belts in central Asia and Mongolia and some Precambrian cratonic orogenic belts.
90% of the world's ultra-large porphyry copper deposits are concentrated in the Pacific rim, especially in the passive continental margin of the eastern Pacific belt and the west coast of the Pacific Ocean.
In the sanjiang metallogenic belt in southwest China, yulong in Tibet was discovered in the late 20th century, and pulang in yunnan was discovered since the 21st century.In the gangdith metallogenic belt, chulong, xiongcun, dorong and jiama (porphyry - hornstone type) large-superlarge copper deposits have been discovered.
Petrological and geochemical characteristics
Petrology: the porphyry copper deposit is mainly related to the calc-alkali series porphyry intrusive bodies in space, time and origin, that is to say, it is related to the diorite porphyry - granodiorite porphyry - quartz monosporphyry, especially the majority of granodiorite porphyry and quartz monosporphyry.The porphyry bodies are generally related to the calc-alkaline volcanic eruptive activities of andesite and dacite.The intrusive bodies are mainly shallow and ultra-shallow facies, and few are mesopeptic facies.The porphyry associated with the porphyry copper deposit is a passive emplacement controlled by the structure, and the exposed area of the porphyry is not large, generally no more than 2 square kilometers.
Geochemistry: the geochemical characteristics of porphyry bodies are: generally CaO+Na2O+K2O>Al2O3>Na2O+K2O(mole number), usually K2O> Na2O, the initial ratio of strontium is small, generally 0.703~0.706, a few can reach 0.709(Sillitoe,1987;Rui zongyao et al. , 1984;The present ratio of the upper mantle is 0.704±0.002.Platinum-rich group elements (tang renli et al.,1995).The mean value is 0, which is basically consistent with the sulfur isotopes in the mantle. Although the mantle is heterogeneous, its variation range is -3~3(Chaussidon and Lorand, 1990).The REE characteristics of ore-bearing porphyry are between oceanic basalt and crustal granitic rocks and close to oceanic basalt.
Generally speaking, the source area of porphyry copper deposit should be dominated by oceanic crust or upper mantle, and some mixed crustal materials.