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Marbles from Dabieshan and Sulu, China, suffered ultra high pressure (UHP) metamorphism in the coesite-eclogite facies at approximately 700 o C and 30 kbars during Triassic continental collision and subduction. The marbles range in isotopic composition from +7 to +25 δ 18 O VSMOW and from 0 to +6 δ 13 C VPDB . High...
Diamond-bearing carbonate rocks from Kumdy-Kol, Kokchetav massif, Kazakhstan, were strongly altered by fluids flowing through fractures and infiltrating along grain boundaries during exhumation. Alteration includes retrogradation of high-grade silicate assemblages by hydrous minerals, replacement of diamond by graphite and of dolomite by calcite. Diamond-bearing carbonate rocks are among the most...
A number of models of continental collision already exist, but the role of foregoing oceanic plate subduction or variable coupling between plates still remains to be explored. In addition, heat generation by radioactive decay may be quite variable. For example, our geochemical data from low-to-high grade metamorphic rocks of the Lesser and Higher Himalayan sequences reveal measured heat production...
Two-dimensional numerical modeling of early continental collision associated with subduction of the lithospheric mantle shows that the formation and exhumation of coesite- and diamond-bearing rocks metamorphosed at 700 to 900 °C in the presence of dense supercritical silicate fluids and melts may be explained by a transient “hot channel effect”. Anomalously high temperature is caused by intense viscous...
There was much debate recently on the mechanisms of continental convergence and related pressure–temperature (P–T) conditions, both in modeling and petrologic community. Depending on the mechanisms of convergence (subduction, collision, folding or RT instability) one can argue about the possibility of large-scale deviations of pressure and temperature in the accretion prism and below it, from “reference”...
The Eocene volcano-sedimentary units of Northern Anatolia are confined into a narrow zone trending parallel to the Intra Pontide and İzmir–Ankara–Erzincan sutures, along which the northern branch of the Neotethys Ocean was closed during a period between Late Maastrichtian and Paleocene. The Middle Eocene formations overlie both the imbricated and highly deformed units of the suture zone, which are...
The ‘Indosinian Orogeny’ is defined in a broad sense as encompassing all the Late Paleozoic to Early Mesozoic tectonic events associated with the closure of the eastern parts of the Paleo-Tethys Ocean. It includes the Permo-Triassic continent–continent collision between the North China and South China blocks that generated the Qinling–Dabie–Sulu orogen containing the largest ultrahigh-pressure (UHP)...
In the Yangbajing area, southern Tibet, several monogenic volcanoes were conformably superimposed on the Linzizong calc-alkaline volcanic successions. According to their petrologic and geochemical characteristics, these monogenic volcanoes are composed of three rock varieties: tephritic phonolitic plugs and shoshonitic and trachytic lavas. Their geochemical systematics reveals that low-pressure evolutionary...
U–Pb ages, trace elements, and Hf isotope compositions of zircons from the Mayuan migmatite complex in NW Fujian province have been determined to provide constraints on the source and genesis of anatexis and tectonothermal evolution related to the Caledonian orogeny in South China. The migmatites investigated consist of various amounts of mesosome, leucosome, and melansome. Zircons extracted from...
In-situ SIMS analyses of O and U–Pb isotopes as well as LA-(MC)-ICPMS analyses of trace elements, U–Pb, and Lu–Hf isotopes were carried out for zircon from a quartz vein and its host UHP eclogite in the Dabie orogen. The results are integrated to decipher the effect of aqueous fluid on the new growth of metamorphic zircon and on the recrystallization of protolith zircon during continental subduction-zone...
A combined study of mineral compositions and zircon U–Pb ages was carried out for a zoisite―quartz vein and its host retrograded eclogite in the Dabie orogen. The results reveal two episodes of fluid action during exhumation of the deeply subducted continental crust. The vein has a mineral paragenesis of quartz+zoisite+epidote+white mica+garnet+rutile+zircon+apatite, which is almost the same as that...
An integrated study of petrology, geochronology and geochemistry was performed for ultrahigh-pressure metamorphic gneisses in the Sulu orogen. The results are used to elucidate the polyphase growth of such metamorphic minerals as zircon, titanite and garnet in response to pressure–temperature changes and fluid/melt action during continental collision. This provides insights into the property of metamorphic...
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...
Multiphase solid (MS) inclusions in both garnet and omphacite were investigated for zoisite-bearing eclogite from the ultrahigh-pressure (UHP) metamorphic zone in the Sulu orogen. The results provide petrological evidence for local anatexis during exhumation of deeply subducted continental crust. There are three types of MS inclusions: (1) plagioclase+quartz, (2) plagioclase+quartz+K-feldspar, and...
The Ceará Central Domain of the Borborema Province is a key tectonic domain within the 5000km-long West Gondwana Orogen, which extends from Algeria in Africa to Central Brazil. Igneous rocks of the Tamboril-Santa Quitéria Complex, investigated in this study, record a long-lived history of convergent magmatism and crustal anatexis. SHRIMP U-Pb dating and Hf-O isotope analyses of zircons from granitoids...
Phanerozoic high-Mg diorites and granodiorites are known to be related to diverse subduction styles at convergent margin settings but have not been linked to collision processes. The Santonggou complex in the eastern Kunlun Orogen is composed of a dominant granodiorite intruded by small stocks and dykes of porphyritic granodiorites and diorites, which are all characterized by high MgO and Ni but low...
Highly retrogressed eclogite is present in the Stak massif located on the northern edge of the Indian continental margin in northern Pakistan. Garnet in foliated samples contains omphacite inclusions (Xjd=0.33–0.40) and quartz inclusions and latter retain Raman spectroscopic evidence for high residual pressures up to 0.52GPa. These garnet grains do not show apparent compositional zoning. By contrast,...
Utilizing microstructures of Cl-bearing biotite in pelitic and felsic metamorphic rocks, the timing of Cl-rich fluid infiltration is correlated with the pressure-temperature-time (P-T-t) path of upper amphibolite- to granulite-facies metamorphic rocks from Perlebandet, Sør Rondane Mountains (SRM), East Antarctica. Microstructural observation indicates that the stable Al2SiO5 polymorph changed from...
The Gubaoquan eclogite occurs in the Paleozoic Beishan Orogen of NW China. Previously it has been interpreted as a fragment of subducted oceanic crust that was emplaced as a mélange within continental rocks. Contrary to this, we demonstrate that the Gubaoquan eclogite protolith was a Neoproterozoic basic dyke/sill which intruded into Proterozoic continental rocks. The SHRIMP UPb zircon dating of the...
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