Continuity of the North Qilian and North Qinling orogenic belts, Central Orogenic System of China: Evidence from newly discovered Paleozoic adakitic rocks

Petrogenesis of Aoyougou high-silica adakite in the North Qilian orogen, NW China: Evidence for decompression melting of oceanic slab

“…On the basis of rock types and forming mechanisms, it is generally thought that adakite can be achieved by three ways: (1) partial melting of subducted slab [1][2][3][4][5][6]14], (2) partial melting of thickened lower crust [15][16][17][18][19][20][21]25], and (3) highpressure fractional crystallization of basaltic magma [22,24]. The Aoyougou trondhjemitic rocks have I Sr of 0.7044-0.7047 and  Nd (t) of 3.0-4.1, suggesting that they are originated from a juvenile oceanic crust rather than the old continental lower crust.…”

“…On the other hand, back-arc basin basalts (BABB) have geochemical characteristics of both IAB and MORB [61][62][63], with variations depending on extents and positions of partial [4,14,58,64], continental lower crust [25,65,66] and eclogites from the North Qaidam [59].…”

“…Adakite is originally linked to melting of young and hot slab, and mainly distributes in the circum-Pacific margins [7,8,13,14]. However, recent studies have revealed that partial melting of thickened lower crust and differentiation of parental basaltic magma at high pressure are also possible mechanisms [15][16][17][18][19][20][21][22][23][24][25]. This implies that adakite is of diverse derivation and the slab melting model, to some extent, has defect as extremely limited conditions for melting, thus prerequisites such as high geothermal gradient, relatively hot and juvenile slab, flat subduction and slab window have been proposed [1,6,7,26].…”

An Early Cretaceous garnet-bearing metaluminous A-type granite intrusion in the East Qinling Orogen, central China: Petrological, mineralogical and geochemical constraints

“…It has a prolonged Precambrian history (Zhang et al, 1996;Zhu et al, 2011) and was mainly built by two collisional events during EarlyeMiddle Paleozoic and Early Mesozoic and the Shangdan and Mianlue suture zones formed during these collisions (Ratschbacher et al, 2003;S.Z. Li et al, 2007;Tseng et al, 2009;Xiang et al, 2011). Geographically, it is commonly separated into a western and an eastern orogen.…”

Proterozoic rapakivi granites from the North Qaidam orogen, NW China: Implications for basement attribution

“…Chen et al, 2009). Farther north, an early Paleozoic suture (Maruyama, 1997;Tseng et al, 2009) characterized by blueschist, eclogite and ophiolites (Song et al, 2007b;Zhang et al, 2007) extends between the Alxa terrane (western part of the NCC) and the Qilian terrane.…”