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A detailed mineralogical and textural study of two pyroxenites from the Beni Bousera massif, a garnet clinopyroxenite (GP) and a garnet clinopyroxenite containing graphite pseudomorphs after diamond (GGP), indicates a strong metamorphic overprint associated with the massif exhumation. In both pyroxenites, the primary assemblage [Cpx(I)+Gt(I)±Opx] originally stable with diamond, records temperatures...
Back-arc volcanism in the western Argentinian provinces of Mendoza and Neuquén has been widespread from the Miocene to historic times. We present a detailed investigation of profiles through two of the major Miocene volcanic areas of the region, the neighboring Huantraico and La Matancilla plateaus, including new 40 Ar/ 39 Ar age results of major and trace elements as well as Nd, Sr...
The Dunhuang Block, located in the eastern Tarim Craton, widely exposes Precambrian TTG gneisses and metamorphosed supracrustal rocks. A suite of metasedimentary rocks of the Dunhuang Group in the Hongliuxia area on the eastern margin of the Tarim Craton are characterized by moderate contents of quartz, plagioclase, and biotite, with minor amounts of garnet or kyanite, most of which have experienced...
Normal mid-ocean ridge basalts (MORBs) from the Southwest Indian Ridge (SWIR) (48°E–64°E) have larger ranges of 187 Os/ 188 Os ratios from 0.1295 to 0.3023 than previously reported N-MORBs. 187 Os/ 188 Os ratios show positive correlations with 1/Os, suggesting possible contamination from a component with higher 187 Os/ 188 Os ratios. Mixing modeling...
The Jinan gabbroic intrusion from the North China Block (NCB) experienced complex differentiation from a reduced and Si-undersaturated magma to an oxidized and Si-saturated melt, with a mineral assemblage of olivine+pyroxene+plagioclase+biotite+ilmenite. New dating of baddeleyite and zircon yield a consistent U–Pb age range from 130 to 134Ma, confirming emplacement during the early Cretaceous. In...
The Lake Natron–Engaruka Monogenetic Volcanic Field (LNE-MVF) in northern Tanzania consists of more than 150 vents of Upper Pleistocene to Holocene age that are scattered over an area of 2500km 2 . Here we describe the petrological characteristics of these eruptions in detail and link the magma chemistry to eruptive behavior when the magmas reach the surface. Erupted magmas are predominantly...
Rock specimens collected from lower, middle, and upper portions of the exhumed Himalayan mid-crust in the upper Tama Kosi region of east-central Nepal yield pressure–temperature–time–deformation (P–T–t–D) paths that demonstrate the presence of a structural, metamorphic, and geochronologic discontinuity. A P–T–t–D path from below the discontinuity defines a loading path with deformation at staurolite-grade...
The Upper Jurassic volcanic rocks of the Pre-Cordillera and High Andes of northern Chile (26–31°S) represent a back-arc magmatic chain formed during an earlier stage of Andean subduction. After the Callovian, the back-arc basin gradually changed from marine to continental conditions and was characterized by basaltic to rhyolitic rocks erupted along two belts, parallel to the coeval arc. The western...
The Henties Bay-Outjo dyke swarm (HOD) in NW Namibia presents a well-exposed example of the magma feeder system for continental flood basalts. This study uses bulk-rock, mineral and melt inclusion compositions from dyke samples to define pressure–temperature crystallization conditions and thus contributes to the understanding of the magma plumbing and storage beneath the province. The thermobarometry...
Gahnite (ZnAl 2 O 4 ), chrysoberyl (BeAl 2 O 4 ) and beryl (Be 3 Al 2 Si 6 O 18 ) have been found as accessory minerals in the external, highly fractionated, leucogranitic unit within the Hercynian reversely zoned Belvís de Monroy pluton (westernmost part of the Montes de Toledo batholith, Cáceres, Spain). The highly felsic (SiO 2...
In this paper we present detailed field observations, petrology, and geochemical data, and discuss the petrogenetic aspects of the unusual high Mg-mafic dikes of alkaline to subalkaline nature from the widely known Paleo-proterozoic Mahbubnagar Large Igneous Province. These dikes traverse the granitoids of the peninsular Gneissic Complex and the 2.7Ga metabasalts in the adjacent Gadwal greenstone...
The tectonic properties of the Erlangping unit and the subduction polarity of oceanic basins in the North Qinling–Tongbai orogen have been the focus of debate for more than twenty years. The resolution of these controversies hinges on the refined constraints on the location and nature of subduction-related magmatism. In this contribution, we provide a combined study of zircon U–Pb ages, major and...
The leucogranites in the Baoshan Block of the Tethyan belt in Western Yunnan, are composed mainly of two-mica granite with subordinate muscovite granite. Here we present zircon U–Pb ages from four intrusions that show ages of 448–476Ma suggesting that these rocks were emplaced during the Ordovician. The leucogranites are high-K calc-alkaline and strongly peraluminous, with K 2 O/Na 2 ...
The Güira de Jauco Amphibolite Complex underlies the Mayarí–Baracoa Ophiolitic Belt (eastern Cuba) and is composed of highly foliated amphibolite, locally with blocks of sheared serpentinitie that enclose concordant layers of amphibolite. These amphibolites are interpreted as remnants of a sub-ophiolitic metamorphic sole likely formed during late Cretaceous times before the initiation of the collision...
Granitoids (175-80Ma) representing a prominent Yanshanian (Jurassic to Cretaceous) magmatic event in South China widely intrude the Precambrian crystalline basement and Paleozoic strata. Here we report zircon U-Pb age data, geochemical characteristics and Sr-Nd isotopes of the Late Jurassic and Early Cretaceous granitoids from the northwestern Zhejiang Province (ZXB) of southeastern China. Our results...
Early Permian magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt (CAOB). Early Permian granitic magmatism has been recognized from southern Beishan, NW China and they were emplaced between 275Ma and 279Ma according to LA-ICPMS zircon U–Pb dating. They are mainly metaluminous I-type and belong to the high-K calc-alkaline and shoshonitic series. The granitoids...
The formation and exhumation of Variscan high- to ultrahigh-pressure metamorphic rocks from the Moldanubian Zone in the Bohemian Massif are the subject of controversy regarding their unclear relationship to possible subduction zones. In this paper we present the results of a petrological study of eclogites that occur together with serpentinites within amphibolite facies gneisses in the Moldanubian...
The Fuchuan ophiolite occurs along the easternmost domain of the Jiangnan Orogen, considered as the suture between Yangtze and Cathaysia Blocks in South China. Here we report results from our new field observations, zircon U–Pb ages and Hf isotope of the cumulate units, chemistry and tectonic discrimination of Cr-spinel from the harzburgite, and whole rock geochemistry of the pillow lava from the...
The Gangdese belt, Tibet, records the opening and closure of the Neo-Tethyan ocean and the resultant collision between the Indian and Eurasian plates. Mesozoic magmatic rocks generated through subduction of the Tethyan oceanic slab constitute the main component of the Gangdese belt, and play a crucial role in understanding the formation and evolution of the Neo-Tethyan tectonic realm. U–Pb and Lu–Hf...
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