Postsubduction porphyry Cu-Au and epithermal Au deposits: Products of remelting of subduction-modified lithosphere

Double-layer structure of the crust beneath the Zhongdian arc, SW China: U–Pb geochronology and Hf isotope evidence

“…Unlike normal arc magmas, the Cu-bearing porphyries in the Zhongdian arc are potassic, relatively oxidized, and adakitic, and they were derived from a juvenile lower crust formed by underplating of former arc basaltic magmas, as discussed above. Re-melting and remobilization of underplated mafic material (including sulfide-bearing metal-rich cumulates at the base of the crust that formed during the earlier arc magmatism) probably provided the Cu, Au, and S for the porphyry Cu systems (Richards, 2009;Lee et al, 2012;R. Wang et al, 2014;Hou et al, 2015).…”

“…In addition, the pervasive biotite phenocrysts and hydrothermal alteration of the ore-bearing porphyries in the Zhongdian arc indicate high magmatic water contents ($4 wt.%), which is also a critical factor in the generation of porphyry Cu deposits (Richards, 2003(Richards, , 2009Hou et al, , 2013a. The high H 2 O content of these porphyries can probably be attributed to the melting of H 2 O-bearing amphibolite cumulates that were the residues of underplated arc magmas, and which then saw the breakdown of hornblende, thus releasing H 2 O (Richards, 2009). Metal-rich cumulates in the early-stage juvenile crust probably contributed to the enrichment of ore-forming elements (Lee et al, 2012), and subsequently the slab break-off or slab-tearing may have provided enough heat to fuse the juvenile lower crust.…”

“…Wang et al, 2014;Hou et al, 2015). In addition, the pervasive biotite phenocrysts and hydrothermal alteration of the ore-bearing porphyries in the Zhongdian arc indicate high magmatic water contents ($4 wt.%), which is also a critical factor in the generation of porphyry Cu deposits (Richards, 2003(Richards, , 2009Hou et al, , 2013a. The high H 2 O content of these porphyries can probably be attributed to the melting of H 2 O-bearing amphibolite cumulates that were the residues of underplated arc magmas, and which then saw the breakdown of hornblende, thus releasing H 2 O (Richards, 2009).…”

Porphyry copper assessment of the Tethys region of western and southern Asia: Chapter V in <i>Global mineral resource assessment</i>

“…Several porphyry deposits in Turkey, the Lesser Caucasus, and Iran may represent examples of this family (Hou and others, 2011). Their geology and mineralization style are broadly similar to subductionrelated porphyry copper deposits; however, the magmas that are associated with them originated from as-yet only partially understood mantle-involved processes (Richards, 2009;Richards and Kerrich, 2007).…”

“…Given that important porphyry copper mineralization has been recognized in this tectonic environment (Richards, 2009;Richards and Kerrich, 2007), more detailed documentation on the timing of collisional events and associated postcollisional magmatism through time is warranted. Several observations regarding the nature of postcollisional (or postsubduction) magmatism in the Tethys region of western and southern Asia include:…”