Where were the Metal, Sulfur and Water from in the Postcollisional Porphyry Cu Deposit at Qulong in South Tibet?

Objective Most porphyry Cu deposits （PCDs） were formed in association with subduction-related calc-alkaline magmas, which occurred widely in magmatic arcs worldwide. A widely accepted model is that such deposits were formed from hydrothermal fluids exsolved from hydrous, high oxygen fugacity, sulfur-rich arc magmas, derived from a mantle wedge metasomatized by subduction-slab fluids. Recent studies have documented that such deposits may also occur in post-collisional settings, e.g., the Gangdese porphyry Cu belts in Tibet. The formation of such PCDs is very difficult to be explained by the classic PCDs model, which results in an alternative model to be proposed to interpret the genesis of PCDs in such settings. In this alternative model, metals and sulfur of the post-collisional PCDs were generally thought to be derived from a subduction-modified thickened lower crust, rather than a metasomatized mantle wedge. However, our detailed analysis suggests that the sources of metals and sulfur for the PCDs in post-collisional settings still cannot be well explained by the lower-crust melting model.

Postcollisional mantle-derived magmatism, underplating and implications for basement of the Junggar Basin

The late Paleozoic postcollisional granitoids, mafic-ultramafic complexes, and volcanic rocks are extensively distributed around the Junggar Basin; they are generally characterized by positive εNd（t） values, implying that the magmas were mantle-derived and contaminated with crustal materials to some extents. The emplacement of mantle-derived magmas and their differentiates in the upper crust is the expression of deep geological processes at shallow level, while much more mantle-derived magmas were underplated in the lower crust and the region near the crust-mantle boundary, being component part of basement of the Junggar Basin. The postcollisional mafic-ultramafic complexes would not be generated by re-melting of residual oceanic crust, which was considered as the basement of the Junggar Basin, unless very high degrees of partial melting occurred. Even if old continental crust had been present before collision, it would have been strongly modified by the mantle-derived magma underplating. This

Petrochemistry ,Chronology and Tectonic Setting of Strong Peraluminous Anatectic Granitoids in Yunkai Orogenic Belt , Western Guangdong Province ,China

Arguments persist on the genesis and ages for the banded-augen （rapakivi） anatectic granitoids （charnockite） extensively outcropped in the Yunkai （云开） region, western Guangdong （广东） Province. Their petrochemistry, SHRIMP dating, deformational and metamorphic structure were studled. The results show that most granitoids are A/CNK〉1. 1, CaO/Na2O= 0. 62-1. 61 （average 0.94〉0.3）, Al2O3/TiO2 =16.6-60.6 （average 23.68）, depleted high field strong elements Ta, Nb, Zr, strong peraluminous high-K calcalkaline and calcalkaline granitoids in the post-collisional tectonic environment of a subduction-collision orogenic belt in an active-continental margin. The temperatures of charnockite and gneissic garnet-bearing biotite monzonitic granite are obviously higher than those of banded-augen （rapakivi） biotite monzonitic granite, and charnockite and gneissic garnet-bearing biotite monzonitic granite with the evolutional characteristics of A-type granites. The forming ages from banded-augen （rapakivi） biotite monzonitic granite to charnockite and gneissic garnet-bearing biotite monzonitic granite, whose crystallizing zircon SHRIMP ages are （465±10） Ma, （467±10 ） Ma, （435±11 ） Ma and （413±8） Ma, respectively, become younger. This shows that there was an oceaniccontinental subduction-collision and post-collisional extension-delamination-underplating between the Yangtze and Cathaysia plates during the Caledonian, and the granitoids experienced compressional uplift and extensional exhumation during the lndosinian. This provides important evidence of subduction collision of the Yangtze plate to the Cathaysia plate during the Caledonian in South China.