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The late Cenozoic Anatolian Metallogenic Trend in Turkey is a manifestation of westerly Aegean subduction and easterly Arabian continental collision along the Western Tethyan Orogenic Belt. The 1500 × 200 km late Cenozoic Anatolian magmatism hosts many gold-rich porphyry and epithermal deposits and prospects (~ 27 Moz Au) that formed during the tearing of the Aegean slab and Arabian slab break-off events that initiated at 15 Ma in western Anatolia and 25 Ma in eastern Anatolia. Although the temporal and spatial correlations between slab segmentation, late Cenozoic magmatism, and associated gold-rich porphyry and epithermal mineralization has been intuitively proposed, the genetic relationships between asthenospheric upwelling, subcontinental lithospheric mantle instability, and magma fertility have not been well established. Herein, new geochemical and radiogenic Sr, Nd, and Pb isotope data from Miocene to Pliocene magmatic rocks that are genetically related to porphyry, epithermal, and skarn systems from western, central, and eastern Anatolia are presented and interpreted with previously published geochemical data from late Cenozoic intrusion-related mineral systems throughout Anatolia. The magma fertility of the late Cenozoic post-subduction igneous suites along the late Cenozoic Anatolian Metallogenic Trend is assessed and is best indicated by the SiO2 (61.8 ± 5.5 wt%) content, Sr/Y (> 20) and Ba/Ta ratios (> 428), and (εNd)i values (< 0). Fertile magmatism dominantly resulted from the melting of the metasomatized Anatolian SCLM and was accompanied by amphibole ± clinopyroxene and plagioclase fractionation in the absence of garnet residue as indicated by low (Dy/Yb)N and Eun/Eu* ratios. Magma fertility indicators evolved through time along the late Cenozoic Anatolian Metallogenic Trend. In western Anatolia, fertile magmatism peaked in the middle to late Miocene (15–9 Ma) and was preceded by less-fertile early Miocene magmatism (21–18 Ma) and followed by barren Pliocene to Quaternary, alkaline lavas. The geochemical signatures of mineralized igneous units in central and eastern Anatolia indicate that fertile magmas formed early as regional magmatism evolved towards less hydrous, less oxidized, shallower, and mantle-dominant signature. The reduction of magmatic fertility since the late Miocene throughout Anatolia was caused by the upwelling of hot, dry asthenosphere through the Aegean slab tear and Arabian slab break-off, SCLM instability, and subsequent removal in absence of an over-thickened crust. The spatial migration of slab ruptures and slab gap opening modified mantle fluxes, reduced the SCLM thickness and volume of fusible material, and caused the migration of melting source. Thus, the segmentation of the Southern Neotethyan oceanic slab triggered the metallogenic events along the Anatolian Trend but subsequently contributed to the cessation of production of fertile magma. [ABSTRACT FROM AUTHOR]

Coeval potassic adakite-like and shoshonitic felsic intrusions in the western Yunnan province of SW China are spatially and temporally associated with Eocene–Oligocene shoshonitic mafic volcanic rocks. The shoshonitic syenite and quartz monzonite intrusions are characterized by high K2O contents (4·9–6·8 wt %) and K2O/Na2O ratios (1·1–1·7), high Y (1·7–34·8 ppm) and Yb (1·50–3·16 ppm) contents, nearly flat heavy rare earth element (HREE) patterns and moderate Eu anomalies (Eu/Eu* = 0·65–0·78). The potassic adakite-like granite and quartz monzonite intrusions are characterized by enrichment in light rare earth elements (LREE), depletion in HREE and fractionated HREE patterns, high Sr (328–1423 ppm), Sr/Y (38–243) and La/Yb (23–62), and low Y and Yb contents. The shoshonitic syenite and quartz monzonites have the same Sr–Nd–Pb isotope compositions as the shoshonitic mafic volcanic rocks. They define linear trends on Harker diagrams, and have similar REE and trace element patterns to the shoshonitic mafic volcanic rocks. These observations suggest that the shoshonitic syenite and quartz monzonite magmas were differentiated from parental shoshonitic mafic melts by fractional crystallization of olivine, clinopyroxene and feldspar. The parent magmas originated from a metasomatized lithospheric mantle source. The shoshonitic syenite and quartz monzonites have higher magmatic zircon δ18O values (6·26–7·05‰) than the mantle, which suggests some 18O enrichment during earlier subduction-related metasomatism of their lithospheric mantle source. The potassic adakite-like granites have Sr–Nd–Pb isotopic compositions that overlap those of lower-crustal amphibolites. They have low Mg#, MgO, Ni and Cr contents, abundant inherited zircons, high zircon &varepsilon;Hf (0–5·5) and mantle-like δ18O (4·78–6·25‰) values. These granites were plausibly derived by partial melting of a thickened, potassic, mafic, lower crust with minor input from an older igneous felsic component. The potassic adakite-like quartz monzonites contain abundant mafic microgranular enclaves, and have transitional major and trace element characteristics between the adakite-like granite and the shoshonitic mafic magma. The quartz monzonites generally have higher Mg#, MgO, Ni and Cr contents than the lower crust-derived adakite-like rocks. They have no inherited zircons and have uniform zircon &varepsilon;Hf and δ18O values. It is suggested that they were derived by variable degrees of mixing between lower-crustal melts and shoshonitic mafic magmas. The coeval shoshonitic and potassic adakite-like rocks appear to be associated with thinning of overthickened lithospheric mantle along the trans-lithospheric Jinsha suture following the collision between India and Asia. This lithospheric thinning could have resulted in the upwelling of the asthenosphere beneath western Yunnan, which induced partial melting of the residual metasomatized lithospheric mantle as well as the thickened lower crust in the Eocene. [ABSTRACT FROM AUTHOR]