How Do Porphyry Copper Deposits Form
Porphyry copper deposits (porphyry copper deposits) are usually rich communities of disseminated, veinle-disseminated and veinle-shaped copper and molybdenum-copper components symbiotic with granite intrusions of porphyry structure.И.Г.Pavlova put forward 10 characteristics of porphyry copper deposits that can be distinguished from other endogenous deposits:
(1) with the characteristics of network veinlets;
(2) the composition of the major metallic minerals (pyrite, magnetite, chalcopyrite, pyroxene, and in some deposits porphyry, thioarsenite, and pyrite) and the associated nonmetallic minerals (quartz, sericite, potassium feldspar, biotite, kaolinite, etc.) is stable;
(3) the average content of copper is relatively low in primary ores (0.3-0.8%), but significantly higher in oxidized ores (1-1.5%), while the distribution of molybdenum in primary oxidized ores is relatively uniform (0.005-0.05%). In this case, the ratio of copper to molybdenum in ores varies greatly, forming a series of important copper, copper-gold and copper-molybdenum deposits.
(4) mineralization and mainly neutral porphyry intrusions (granodiorite porphyry, quartz monastic porphyry), and a few slightly acidic (granoporphyry,
It is spatially related to the basic-biased intrusive body (diorite porphyry).
(5) mineralization may occur directly in the porphyry intrusive body, or in the surrounding rocks -- volcanic rocks, intrusive rocks and metamorphic rocks in the external contact zone immediately adjacent to the intrusive body;
(6) ore bodies are developed in the zone where hydrothermal alteration rocks are widely found. The alteration rocks are serician-quartzite, biomica-potassium feldspar, argillaceous and qingpanrock-type metasomatism rocks.
(7) according to the maximum value of metallic elements and the main symbiotic non-metallic minerals (2), the stable zonation in orebodies and hydrothermal rocks can be written in the following order.Fe3+ one Mo(Cu) one Cu(Mo) one Cu(Ag) one Fe2+(Au) one Pb one Zn (Au, Ag);
(2) biotite - potassium feldspar, sericite, quartz, montmorillonite, kaolin, qingpanyan
(8) the huge reserves of the deposit guarantee the large-scale mining of ore, low cost and the possibility of open pit mining.
(9) the occurrence of rich ore related to oxidation formed secondary sulfide enrichment zone covering poorer primary ore
(10) the porphyry copper deposits were formed at different developmental stages in the geosynclinal fold area (plate active edge).It can be formed before the main stage of the fold (in the island arc stage) with the magmatism of the geosyncline, and related to the porphyry intrusions and sub-volcanic rocks in the orogenic stage and activation stage (intraplate fault zone).
In the modern classification of many porphyry copper deposits, the following features are taken into account, not only in terms of individual features, but also in terms of combinations of features :(1) the location of geotectonics and paleotectonics;(2) mineral-bearing magma formation and composition of mineral-bearing porphyry facies formed (3) crust thickness and composition intruded by mineral-bearing magma formation;(4) by R.H.The occurrence of ore bodies in the porphyry copper system classified by silito (5) the formation depth of ore-bearing magmatic rock mass, (6) whether there is breccia tube;(7) the composition of the main ore and the ore with an admixture;(8) zonal characteristics of metallic ore; (9) composition and zonal properties of hydrothermal altered rocks; (10) morphological characteristics of ore-bearing intrusive bodies and ore-bearing bodies.