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The Neoproterozoic period is a key geological time in earth history that witnessed the breakup of the Rodinia supercontinent. The Diancangshan and Ailaoshan Massifs are two major segments along the Ailaoshan tectonic zone, and the Neoproterozoic metamorphic igneous rocks in these massifs preserve key clues to elucidate the on-going dispute over the geodynamic drives for the break-up of Rodinia. Many...
Santorini volcano sits ~145 km above the Aegean Wadati-Benioff zone, where the African plate subducts northward beneath Eurasia. There are only a few localities in the whole Aegean where basaltic lavas primitive enough to constrain mantle processes beneath the Aegean arc can be found; in this work we analyzed one such locality, a basalt lava from the southern part of Santorini. We apply a suite of...
The Hart River sills are a set of mafic to intermediate intrusions that occur in northern Yukon, Canada. The largest sills are over 500 m thick and over 200 km long. New U-Pb dates of 1382.15 ± 0.39 Ma and 1382.14 ± 0.36 Ma were obtained via chemical abrasion thermal ionization mass spectrometry on zircon. Whole rock initial neodymium isotopic compositions of the Hart River sills are juvenile and...
The contributions of magmatic processes such as fractional crystallization and magma mixing to the composition of intermediate volcanics are enigmatic. This is mainly attributed to the difficulty in deciphering the composition of primary melts. Here, we address this issue through a combined geochemical and petrological study of clinopyroxene phenocrysts in intermediate volcanics from the Middle-Lower...
Intense Cenozoic magmatism accompanied the convergence and collision of the Eurasian, African and Arabian plates. In the Cappadocia Region of Central Anatolia, widespread and abundant volcanism developed from the late Miocene to the Quaternary. Calc-alkaline pyroclastic products and lava erupted diffusely during the late Miocene and Pliocene. Both calc-alkaline and Na-alkaline volcanic rocks were...
The geochemical evolution of olivine from primitive magmatic skarn environments has been studied by atmospheric pressure experiments carried out at 1250, 1200, and 1150 °C under QFM oxygen buffering conditions. The starting materials were three synthetic basalts (i.e.,meltMg#78, meltMg#75, and meltMg#72) doped with variable amounts of CaCO3, in order to reproduce the natural concentration levels of...
The origin of large variations in stable and radiogenic isotope compositions of magmas erupted from the Neapolitan volcanoes, including Somma-Vesuvius and Campi Flegrei (Southern Italy), has always been contentious. Indeed, the role and relative importance of sediment subduction versus crustal assimilation to explain the chemical and isotopic variations of the erupted magmas remain unclear. Isotopic...
A composite xenolith composed of a zircon-bearing, apatite-rich olivine-pyroxene hornblendite and an amphibole harzburgite part was found in an outcrop of Neogene alkali basalt at Szigliget, Bakony-Balaton Highland Volcanic Field, Western Hungary. The hornblendite is composed dominantly of amphibole that is strongly enriched in incompatible trace elements along with apatite, orthopyroxene and olivine...
Many models of igneous layered complexes assume that the instantaneous boundary between accumulated grains and overlying magma was horizontal. In the case of the Bushveld Complex, several km of hot, dense magma intruded into low-density sandstones and shales. This unstable density profile and the effect of heating of the floor rocks produced diapirism, features that have been well-documented around...
Globular structures in volcanic and hypabyssal rocks called varioles (or spherulites) have been described from a wide variety of places and rock types including komatiites, basalts, dacites, rhyolites as well as alkaline dykes, but the processes leading to their formation are still debated. Here, we present a field, petrological and geochemical study of variole-bearing lavas (variolites) in the Paleoproterozoic...
Of the isotopically distinctive mantle domains, the so-called HIMU (“high-μ”; μ = 238U/204Pb) source is the most extreme, and its genesis continues to be debated. We report very strong U enrichment at unchanged Th concentrations in Cretaceous oceanic serpentinites with exceptionally high 206Pb/204Pb (reaching 56) but unchanged 208Pb/204Pb. Similar, but less extreme, features are found in 1.9 billion...
The Beila ophiolite is located in the middle part of the Bangong–Nujiang suture zone on the northern Tibetan plateau, and rodingites are widespread within serpentinized peridotites in the ophiolite. According to the mineral assemblages, the Beila rodingite can be divided into three types: Type I rodingites have a mineral assemblage of prehnite, chlorite, and minor diaspore; Type II rodingites comprise...
Strongly peraluminous fractionated S-type granites are important indicators of compositional maturity of the continental crust. Here we report the finding of strongly peraluminous fractionated S-type granites from the western Baoshan Block in the southeastern Tibetan–Himalayan orogenic belt. We present LA ICP-MS zircon U–Pb ages from biotite- and two-mica- granites which reveal two distinct periods...
The Lower Yangtze River Belt in eastern China preserves evidence for widespread Mesozoic magmatism. Geochronological and geochemical studies have been conducted on the magmatic rocks and their associated mineral deposits; however, the relationships and melting conditions of spatially associated I- and A-type granites remain poorly constrained. The Qingyang–Jiuhuashan granitic complex in southern Anhui...
The Imjingang Belt in the Korean Peninsula (KP) attracts much attention because of its critical position in determining the tectonic affiliation of the peninsula. The key to clarifying current controversy lies in the understudied Archaean–Proterozoic basement rocks and Devonian- Carboniferous sedimentary series (i.e.,Imjin Group) in the North Korean part of the belt. In this study, we present geochronological...
Neoproterozoic granitoids from the Delhi Fold Belt in NW India record formation and evolution of the marginal orogen in the Rodinia supercontinent. The ca. 976 Ma Moras I-type granites show variable SiO2 (67.15–75.87 wt%) and CaO (1.10–3.24 wt%) and low REE (59–196 ppm). Their spider diagram is characterized by enrichment of Rb, Th and U and depletion of Na and Ta with positive Pb and negative Sr...
New sensitive high-resolution ion microprobe (SHRIMP) UPb zircon geochronologic data, whole-rock geochemical and Sr-Nd-Pb isotopic data, and zircon and quartz δ18O isotopic data from the Staré Město granitoids (SMG), Jawornik granitoids (JG), and Kłodzko-Złoty Stok granitoids (KZSG) and associated mafic and ultramafic rocks are examined. This study provides new insights into the processes of magma...
Seafloor spreading in the Woodlark Basin is taking place on pre-existing arc crust that was produced by the subduction of the Indo-Australian Plate into the Pocklington Trough (now inactive) to the south during the Paleogene. The Woodlark Basin has a unique tectonic setting characterized by two surrounding subduction zones. To the east, a spreading ridge is also currently being subducted beneath the...
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