Reassessment of continental growth during the accretionary history of the Central Asian Orogenic Belt

We argue that the production of mantle-derived or juvenile continental crust during the accretionary history of the Central Asian Orogenic Belt (CAOB) has been grossly overestimated. This is because previous assessments only considered the Palaeozoic evolution of the belt, whereas its accretionary history already began in the latest Mesoproterozoic. Furthermore, much of the juvenile growth in Central Asia occurred in late Permian and Mesozoic times, after completion of CAOB evolution, and perhaps related to major plume activity. We demonstrate from zircon ages and Nd–Hf isotopic systematics from selected terranes within the CAOB that many Neoproterozoic to Palaeozoic granitoids in the accre…

Zircon reconnaissance dating of Proterozoic gneisses along the Kunene River of northwestern Namibia

Abstract The northern margin of the Epupa Metamorphic Complex (EMC) along the Kunene River in NW Namibia is one of the geologically least known terranes in Africa because of its remoteness and difficult accessibility. We report field relationships and reconnaissance zircon ages for granitoid gneisses from a 120 km foot-traverse along the Kunene River between the Ruacana Falls in the east and Marienfluss in the west. Most rocks are late Palaeoproterozoic in age and correlate well with similar rocks of the EMC farther south in Kaokoland (1757–1835 Ma, one sample 1861 Ma) and with granitoid rocks in the Kamanjab Inlier, some 400 km SE of the Kunene River (1801–1836 Ma). All these rocks constit…

Zircon geochronology and metamorphic evolution of mafic dykes in the Hengshan Complex of northern China: Evidence for late Palaeoproterozoic extension and subsequent high-pressure metamorphism in the North China Craton

Abstract Magmatic and metamorphic zircons have been dated from ductilely deformed gabbroic dykes defining a dyke swarm and signifying crustal extension in the northern part of the Hengshan Complex of the North China Craton. These dykes now occur as boudins and deformed sheets within migmatitic tonalitic, trondhjemitic, granodioritic and granitic gneisses and are conspicuous due to relics of high-pressure granulite or even former eclogite facies garnet + pyroxene-bearing assemblages. SHRIMP ages for magmatic zircons from two dykes reflect the time of dyke emplacement at ∼1915 Ma, whereas metamorphic zircons dated by both SHRIMP and evaporation techniques are consistently in the range 1848–18…

Robert Thomas Pidgeon

Reworking of the Tarim Craton by underplating of mantle plume-derived magmas: Evidence from Neoproterozoic granitoids in the Kuluketage area, NW China

Abstract Most Neoproterozoic granitoids in the Kuluketage area, northern Tarim Craton are characterized by strongly depleted HREE abundances and high Sr/Y and (La/Yb) N ratios, showing typical geochemical features of adakitic rocks. Zircon U–Pb dating of three adakitic plutons yielded Neoproterozoic ages (754 ± 4, 790 ± 3 and 798 ± 3 Ma). The adakitic granitoids exhibit low MgO and TiO 2 contents. Their low Cr, Co and Ni abundances, low ɛ Hf ( t ) values (−21 to −11) and high FeO T /MgO ratios (mostly 2.2–2.9) preclude the possibility of being derived from partial melts of delaminated lower crust. The relatively low ɛ Hf ( t ) values and old Hf two-stage model ages ( T DM 2 = 2 . 42 – 3 .0 …

Deformation history of the Hengshan Complex: Implications for the tectonic evolution of the Trans-North China Orogen

Abstract Structural analysis indicates that the Hengshan Complex underwent five distinct episodes of deformation (D1–D5). The D1 episode formed small isoclinal folds (F1), penetrative axial planar foliations (S1) and mineral stretching lineations (L1). D1 fabrics were reworked by following D2 deformation. Associated with D2 was the development of NW-verging asymmetric folds and accompanying thrust faults. Both D1 and D2 resulted from crustal thickening and coherent with prograde and peak metamorphism. D2 deformation was followed by transpressional dextral shearing (D3), including top-to-NW oblique-slip shearing and NNE–SSW dextral strike-slip shearing. Ongoing collision led to development o…

Age and evolution of a late Archean to Paleoproterozoic upper to lower crustal section in the Wutaishan/Hengshan/Fuping terrain of northern China

Abstract The Taihangshan–Wutaishan area forms part of the central North China Craton and consists of three main components: the Hengshan and Fuping complexes, containing predominantly ductilely deformed late Archean to Paleoproterozoic high-grade granitoid orthogneisses, intruded by mafic dykes of gabbroic composition, and the low-grade late Archean Wutai greenstone belt, developed between the high-grade terrains and consisting of bimodal volcanic rocks and metasediments, associated with coeval granitoids. Zircon dating shows that both the Hengshan and Fuping complexes were intruded by major granitoid bodies between 2.52 and 2.48 Ga, with rare occurrences of 2.7 Ga gneisses. Wutai granitoid…

Lithotectonic elements and geological events in the Hengshan–Wutai–Fuping belt: a synthesis and implications for the evolution of the Trans-North China Orogen

The Hengshan–Wutai–Fuping belt is located in the middle segment of the Trans-North China Orogen, a Palaeoproterozoic continental collisional belt along which the Eastern and Western blocks amalgamated to form the North China Craton. The belt consists of the medium- to high-grade Hengshan and Fuping gneiss complexes and the intervening low- to medium-grade Wutai granite–greenstone terrane, and most igneous rocks in the belt are calc-alkaline and have affinities to magmatic arcs. Previous tectonic models assumed that the Hengshan and Fuping gneiss assemblages were an older basement to the Wutai supracrustal rocks, but recent studies indicate that the three complexes constitute a single, long-…