The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Eclogite lenses in the Agualada Unit (western Ordenes Complex, Spain) contain the peak mineral assemblage garnet (prograde rim: Alm = 48 mol%, Prp = 30 mol%), omphacite (Jd max = 36 mol%), quartz, rutile and rare zoisite, which equilibrated at T = 700 °C and P > 12–14 kbar. Garnet shows discontinuous growth zoning, with a pyrope-poor intermediate zone (Alm = 51 mol%, Prp = 10 mol%) between a core...
In the Dabieshan, the available models for exhumation of ultrahigh-pressure (UHP) rocks are poorly constrained by structural data. A comprehensive structural and kinematic map and a general cross-section of the Dabieshan including its foreland fold belt and the Northern Dabieshan Domain (Foziling and Luzenguang groups) are presented here. South Dabieshan consists from bottom to top of stacked allochtons:...
K-Ar dating, major- and trace-element and Sr-Nd isotopic analyses were carried out for early Cretaceous (122-127 Ma) lamprophyres from the Sulu orogen in eastern China. The results show strong fractionation in rare-earth elements with (LREE) >100 times chondrite, but HREE <10 times chondrite, indicating the presence of residual garnet in the melting source. These rocks are characterized by significant...
Origin and genesis of post-collisional mafic–ultramafic rocks in the Dabie orogen of China are controversial issues with respect to Mesozoic transport of mass and energy between mantle and crust. Zircon U–Pb age, whole-rock major and trace elements, mineral and whole-rock oxygen isotopes, and carbon concentrations and isotope compositions of apatite and whole-rock were determined for these igneous...
In the North Qaidam ultrahigh-pressure (UHP) metamorphic belt, NW China, a large garnet peridotite massif has been exhumed together with felsic gneisses and eclogite during Early Paleozoic continental collision between North China Craton and Qaidam–Qilian Block. Four rock types are recognized in this massif: dunite without garnet, dunite with garnet, garnet lherzolite and garnet pyroxenite. The bulk...
Zircon SHRIMP U–Pb ages and cathodoluminescence (CL) images reveal that most zircon separated from two tonalitic gneiss samples in the northern Dabie high T/P metamorphic zone (NDZ) have four different domains: (1) inherited core, with clear oscillatory zoning, low-P mineral inclusions and high Th/U ratios, indicating the Neoproterozoic age of the protolith; (2) inner-mantle, with homogeneous CL intensity,...
The Slovenska Bistrica ultramafic complex (SBUC; Eastern Alps, Slovenia) occupies the south-easternmost part of the Pohorje Mountains, which represent an exhumed piece of continental crust subducted during the Cretaceous Eo-Alpine orogeny. The SBUC is composed of serpentinised harzburgites with local occurrences of garnet lherzolite, and is the only known occurrence of ultramafic rocks within the...
We investigated the oceanic-type Xiongdian high-pressure eclogites in the western part of the Dabie orogen with combined U–Pb, Lu–Hf, Sm–Nd and Ar–Ar geochronology. Three groups of weighted-mean 206 Pb/ 238 U ages at 315±5, 373±4 and 422±7 Ma are largely consistent with previous dates. In contrast, Lu–Hf and Sm–Nd isochron dates yield identical ages of 268.9±6.9 and 271.3±5.3 Ma. Phengite...
Post-collisional (26–10Ma) high Sr/Y and HREE-depleted intrusive rocks occur in an E–W trending belt paralleling the Yarlung–Zangbo suture in south Tibet. Their petrogenesis has been a subject of debate. Here, we present chronological, geochemical and Sr–Nd–Hf isotopic data for two newly discovered large-volume high Sr/Y granitoids (the Pagu granodiorite and the Nanmuqie granite) and three high Sr/Y...
Low-temperature and high-pressure eclogites with an oceanic affinity in the western part of the Dabie orogen have been investigated with combined Lu–Hf and U–Pb geochronology. These eclogites formed over a range of temperatures (482–565°C and 1.9–2.2GPa). Three eclogites, which were sampled from the Gaoqiao country, yielded Lu–Hf ages of 240.7±1.2Ma, 243.3±4.1Ma and 238.3±1.2Ma, with a corresponding...
The origin of high-Mg adakitic granitoids in collisional orogens can provide important information about the nature of the lower crust and upper mantle during the orogenic process. Late-Triassic high-Mg adakitic granite and its mafic enclaves from the Dongjiangkou area, the Qinling orogenic belt, central China, were derived by partial melting of subducted continental crust and underwent interaction...
Postcollisional mafic to felsic dykes in the western part of the Sulu orogen consist of monzogranite, diorite, plagioclase-bearing hornblendite and gabbro. LA-ICPMS zircon U–Pb dating yielded broadly consistent ages of 111±3 to 129±1Ma for their crystallization, with Neoproterozoic ages of 743±9 to 773±9Ma for residual cores. The mafic to felsic dykes are characterized by the arc-like patterns of...
Formation and exhumation of high-pressure (HP) to ultrahigh-pressure (UHP) metamorphic rocks in continental subduction zones are the two fundamental geodynamic aspects of collisional orogensis. This volume is based on the Session 08c titled “Geochemical processes in continental collision zones” at Goldschmidt 2010 in Knoxville, USA. It focuses on micro- to macro-scale processes that are temporally...
Six samples of the Linglong granitic pluton from the southeastern margin of the North China craton yield similar Jurassic magmatic zircon U–Pb ages and evolved whole-rock Sr–Nd isotopic compositions. They are weakly peraluminous to strongly peraluminous, with A/CNK (molar Al 2 O 3 /[CaO+Na 2 O+K 2 O]) ratios of 1.05 to 1.3 except one sample with an A/CNK of 0.98. However,...
A Late Cretaceous collision of the southernmost portion of the North American continental margin with an undetermined southern block was first established based on the sedimentation history of the plate's supracrustal cover, which is overthrust by harzburgite-dominated nappes of the Guatemala Suture Complex. The collision is also well registered in the metamorphic evolution of continental eclogites...
We present a compilation and comparison of geochemical data of Aegean Eocene to Recent magmatic rocks: (1) North Anatolian Eocene magmatic rocks (NAEM), (2) Aegean to west Anatolian Oligocene–Miocene magmatic rocks (AOMM), (3) Pliocene–Quaternary South Aegean volcanic arc (SAVA), (4) Pliocene–Quaternary Denizli–Isparta volcanics (DIV), and (5) Na-alkaline basalts with intra-plate geochemical affinity...
Little is known about the detailed processes associated with the transition from oceanic to continental lithosphere subduction in the Gangdese Belt of southern Tibet (GBST). Here, we report zircon U–Pb age, major and trace element and Sr–Nd–Hf isotopic data for Late Cretaceous–Early Oligocene (~91–30Ma) intermediate-acid intrusive rocks in the Chanang–Zedong area immediately north of the Yarlung–Tsangpo...
In the plate tectonics theory, continental subduction is pulled by subduction of dense oceanic crust. In practice, however, it is not easy to demonstrate that preceding oceanic crust exposes as oceanic-type eclogite together with continental-type eclogite in collisional orogens. The North Qaidam orogen in northern Tibet is an ultrahigh-pressure (UHP) metamorphic belt that contains the two types of...
Recycling of noble gases from crustal rocks into the mantle is indicated not only by oceanic basalts and mantle xenoliths, but also by ultrahigh-pressure metamorphic rocks in collisional orogens. It is intriguing whether noble gases in continental crust were recycled into the mantle by deep subduction of the continental crust to mantle depths. Here we firstly report the He, Ne and Ar isotopic compositions...
Post-collisional volcanic rocks on the Tibetan Plateau and its margins contain valuable information about the geodynamic processes associated with this Cenozoic continent-continent collision. The Quaternary Tengchong volcanic field at the southeastern margin of the Tibetan Plateau formed high-potassium calc-alkaline volcanic rocks. Herein, we present comprehensive Nd-Sr-Pb-Hf isotopic and elemental...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.