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An Early Paleozoic acid volcanic sequence has been recently detected southeast of Sonid Zuoqi in central Inner Mongolia to constrain the tectonic evolution of the Central Asian Orogenic Belt in this area. First, the volcanic rocks have zircon U–Pb ages of 439–445Ma. They are characterized by (a) a high silica content, moderate alkali content and low iron content; (b) enrichment in light rare earth...
To constrain the source and tectonomagmatic processes that gave rise to the Andong Ultramafic Complex (AUC) in South Korea, we determined the clinopyroxene Sr–Nd–Hf–Pb isotope and trace element compositions as well as the whole-rock and mineral compositions for the Late Triassic (ca. 222Ma) ultramafic rocks from the complex. They are composed of dunites, wehrlites, pyroxene/hornblende peridotites,...
The modal, chemical, and isotopic compositions of mantle peridotite are largely modified by metasomatic processes, which may affect them repeatedly. Xenoliths are commonly used to characterize those metasomatic processes along with the structure, and chemical and isotopic compositions of mantle domains. Nevertheless, the original mantle signatures born by mantle xenoliths are potentially obscured...
Claystone beds directly below and above the Emeishan basalts in SW China formed around the Guadalupian-Lopingian (G−L) boundary. Zircons from both levels give U–Pb ages of ~260Ma, and are identical within-error to ages reported for the Emeishan Large Igneous Province (LIP). The claystones lack Nb−Ta anomalies on primitive mantle normalized elemental diagrams; zircons from these claystones have a geochemical...
Recent studies in the Xiaru and Malashan gneiss dome of the Tethyan Himalaya, southern Tibet identify that Xiaru and Paiku tourmaline-bearing leucogranite dike formed at ~28–29Ma. Together with ~28Ma Kuday garnet-bearing leucogranites, it is demonstrated that the Himalayan orogenic belt experienced a major episode of crustal melting in the Mid-Oligocene. Geochemical data indicate that three suites...
Podiform chromitites have long supplied us with unrivaled information on various mantle processes, including the peridotite-magma reaction, deep-seated magmatic evolution, and mantle dynamics. The recent discovery of ultrahigh-pressure (UHP) chromitites not only sheds light on a different aspect of podiform chromitites, but also changes our understanding of the whole picture of podiform chromitite...
Mesozoic intrusions, including MORB-type gabbros, high-Mg diorites, calc-alkaline diorites and granodiorites, were exposed in the Ando microcontinent that is bounded between the Qiangtang and Lhasa terranes. Discoveries of these Mesozoic intrusions have provided new petrogenetic constraints on our understanding of Bangong-Nujiang ocean evolution. Zircon U–Pb dating shows that these intrusions formed...
We present the whole-rock geochemistry, LA–ICP–MS zircon-apatite U–Pb ages and zircon Hf isotope composition of the granodioritic plutons at the southwestern boundary of Chihuahua with the states of Sinaloa and Sonora. These granodiorites are exposed in the north and south of the Rio El Fuerte in southwest Chihuahua and northern Sinaloa. The magmatism spans over a time period of 37Ma from 90 to 53Ma...
Adakite-like lavas from the Iranian segment of the Arabia–Eurasia collision zone have been considered as partial melts derived from a subducted Neotethyan slab, a hypothesis that cannot be further evaluated due to the lack of systematic age and radiogenic isotopic data. Here, we revisit the Anar region, Iran where such lavas were reported by providing these data to examine their probable origin as...
Coeval high-K calc-alkaline to alkaline granites constitute important components of post-collisional to post-orogenic igneous suites in most orogenic belts of various ages on Earth and their genesis harbors a key to ascertaining critical geodynamic controls on continental crustal formation and differentiation. This zircon U–Pb dating and geochemical study documents three contrasting Early Permian...
Fayalite-bearing felsic (FBF) magmatic rocks are a special type of granitic rocks with controversial origins. A suite of fayalite- and ferrosilite-bearing subvolcanic rocks, namely, the Xishan FBF rocks in South China, is investigated in this study. The Xishan FBF rocks have high SiO2 contents of 69–70wt.%, high K2O/Na2O ratios of 1.71–1.95, and high FeOt/(FeOt+MgO) ratios of 0.88–0.89. Fayalite (Fo=7...
Zircons from seventeen samples of Western Fiordland Orthogneiss (WFO) diorites and three samples of country rock (two schists and one Darran Suite diorite) from the lowermost exposed sections of the Median Batholith, Fiordland, New Zealand, were analysed for in-situ U–Pb and Hf-isotopes. The WFO represents the deeper levels of Early Cretaceous continental arc magmatism on the Pacific margin of Gondwana,...
High-temperature metamorphic rocks are the result of numerous chemical and physical processes that occur during a potentially long-lived thermal evolution. These rocks chart the sequence of events during an orogenic episode including heating, cooling, exhumation and melt interaction, all of which may be interpreted through the elemental and isotopic characteristics of accessory minerals such as zircon,...
Hydrothermal circulation is a fundamental process in the formation and aging of the ocean crust, with the resultant chemical exchange between the crust and oceans comprising a key component of global biogeochemical cycles. Sections of hydrothermally altered ocean crust provide time-integrated records of this chemical exchange. Unfortunately, our knowledge of the nature and extent of hydrothermal exchange...
Oligocene and Miocene Himalayan anatexis is generally thought to have been induced by intracrustal heating or processes without the involvement of mantle-derived heat and materials, suggesting that the Himalayan leucogranites are typical examples of purely crustal melts. This study focuses on a Miocene leucogranite at Langkazi within the Himalayan orogen, an intrusion that contains a large number...
Leucocratic metagabbro and amphibolite from a mafic–ultramafic body within migmatite and granulite in the Kutná Hora Complex were investigated. The mafic–ultramafic rocks show amphibolite facies metamorphism, but in the central part of the body some metagabbro preserves cumulus and intercumulus plagioclase, clinopyroxene and spinel. Spinel forms inclusions in both clinopyroxene and plagioclase and...
A series of dehydration experiments in the piston-cylinder apparatus was carried out at 2GPa and 550–850°C on a natural antigorite sample mixed with 5wt.% of magnetite. Chemical analyses of experimental products show a progressive decrease of the Mg# in antigorite and clinopyroxene between 550 and 675°C, whereas the Mg# of olivine increases. The observed behavior of Mg# signifies Fe–Mg exchange between...
We studied a partially serpentinized peridotite xenolith, found in the diatreme tuff-breccia deposit at Valle Guffari (Hyblean Plateau, southeastern Sicily, Italy), which is representative of the Hyblean peridotite xenolith suite. We also considered all published (21) whole-rock analyses of Hyblean peridotites, to investigate the metasomatizing effects of seawater-related hydrothermal fluids in the...
Ophiolites within Myanmar have been commonly divided into two belts, i.e., the Eastern Belt and Western Belt. The Kalaymyo ophiolite from the Western Belt crops out at the eastern margin of the Indo-Burma Range and was formed during the Early Cretaceous, whereas the Myitkyina ophiolite from the Eastern Belt was formed during the Middle Jurassic. Both ophiolites are characterized by the occurrence...
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