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The relationship between the evolution of Cretaceous magmatism along the southeastern margin of Eurasia and subduction of the paleo-Pacific plate remains controversial. Here we investigate the petrogenesis of the Xiaojiang–Beizhang ferroan and magnesian granitoids, melanocratic microgranular enclaves (MME) that are found within the granitoids, and an associated mafic dyke exposed in southeast China...
This study deals with arc-type and subsequent bimodal volcanic rocks interbedded with (late) Cretaceous sedimentary formations near Gaize, central Tibet that shed new light on the Tethyan evolution along the Bangong-Nujiang suture. Unit I consists of trachyandesites interbedded with fine-grained sandstone, slate, and limestone. Zircon dating on a trachyandesite sample yields a 206Pb/238U age of 99±1Ma...
The Lanong ophiolitic mélange is a typical ophiolitic mélange in the middle section of the Bangong–Nujiang suture zone in northern Tibet. It mainly consists of ultramafic and mafic rocks, and its tectonic setting and formation age remain poorly constrained. In this paper, new geochemical and LA–ICP–MS (laser ablation–inductively coupled plasma mass spectrometer) zircon U–Pb age data obtained from...
There is a Mid–Late Mesozoic (Jurassic–Cretaceous) arc magmatic belt in southern Qiangtang subterrane associated with the north-dipping subduction of the Bangong–Nujiang Tethyan Ocean. Early Mesozoic (Triassic) magmatism, tectonic evolution of the southern Qiangtang subterrane, and the mechanism of its crustal growth, however, remain unclear. This paper reports zircon U–Pb age, whole-rock major, trace...
We present new geochronological, mineralogical, and geochemical data for granitic plutons that crop out within the Zhoushan archipelago, northeastern coastal Zhejiang Province, in order to constrain their origin, and the genetic relationship between the I- and A-type granites. These granites can be divided into two groups: (1) the northern I-type Putuoshan (PTS) and Dadong'ao (DDA) plutons; and (2)...
A major debate related to the evolution of the Tibetan Plateau is centered on whether or not an island arc–back-arc basin system occurred along the Bangong–Nujiang suture zone, central Tibet. Here we present new zircon U–Pb geochronology, rare earth elements (REEs) and bulk-rock geochemistry of these magmatic rocks in the Amdo area, the middle Bangong–Nujiang suture zone, central Tibet, to identify...
Cenozoic continental basalts from Zhejiang Province, southeast China are tholeiitic to weakly alkalic in composition, with moderate MgO contents (6–11wt.%) and an average Mg# of 62. They display typical OIB-like trace element features, including enrichment in most incompatible elements, both LILE and LREE, and negative K, Pb, Zr, Hf anomalies. In particular, they are characterized by high Fe/Mn (73±5),...
Abundant oriented silica precipitates of α-quartz (4.0±1.0vol.%), in part coexisting with calcic amphiboles (<0.2vol.%), have been identified in clinopyroxenes of eclogites from the Weihai area, Sulu ultrahigh pressure terrane, eastern China. Electron backscatter diffraction (EBSD) analyses demonstrate that the majority (97%) of quartz precipitates have topotactic relationships with their host...
Geochemical (including Re-Os isotopic) studies of the mantle rocks of ophiolites in the Bangong-Nujiang suture zone in central Tibet have provided a coherent picture of the evolution of the Bangong-Nujiang Tethyan oceanic mantle from mid-ocean ridge (MOR) to subduction-zone (SSZ) settings.Clinopyroxene (cpx)-harzburgites and lherzolites in the Bangong Lake ophiolite were formed in a MOR setting, as...
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