Showing papers on "Granulite published in 2010"
TL;DR: Rutile is the most common naturally occurring titanium dioxide polymorph and is widely distributed as an accessory mineral in metamorphic rocks ranging from greenschist to eclogite and granulite facies but is also present in igneous rocks, mantle xenoliths, lunar rocks and meteorites.
381 citations
TL;DR: In this article, four meta-sedimentary rock samples, two each from the Yunkai Group and Gaozhou Complex, together with three granite samples, record metamorphic and magmatic zircon ages of 443-430-Ma (Silurian), with many inherited and detrital zircons with the ages mainly ranging from 1.1 to 0.8.
199 citations
TL;DR: In this article, a new T c (x ) model was constructed based on the analyzed age profiles that are described by an error function, which is interpreted to be the extrapolated theoretical absolute temperature of insignificant Pb diffusion in rutile.
178 citations
TL;DR: In this article, the authors show that the Lhasa terrane has undergone two stages of medium-P metamorphism: an early granulite facies event at c. 90 ǫ ma and a late amphibolite facie event at 36-33 ǔ ma.
Abstract: The eastern Himalayan syntaxis in southeastern Tibet consists of the Lhasa terrane, High Himalayan rocks and Indus-Tsangpo suture zone. The Lhasa terrane constitutes the hangingwall of a subduction zone, whereas the High Himalayan rocks represent the subducted Indian continent. Our petrological and geochronological data reveal that the Lhasa terrane has undergone two stages of medium-P metamorphism: an early granulite facies event at c. 90 Ma and a late amphibolite facies event at 36–33 Ma. However, the High Himalayan rocks experienced only a single high-P granulite facies metamorphic event at 37–32 Ma. It is inferred that the Late Cretaceous (c. 90 Ma) medium-P metamorphism of the southern Lhasa terrane resulted from a northward subduction of the Neo-Tethyan ocean, and that the Oligocene (37–32 Ma) high-P (1.8–1.4 GPa) rocks of the High Himalayan and coeval medium-P (0.8–1.1 GPa) rocks of the Lhasa terrane represent paired metamorphic belts that resulted from the northward subduction of the Indian continent beneath Asia. Our results provide robust constraints on the Mesozoic and Cenozoic tectonic evolution of south Tibet.
147 citations
TL;DR: In this article, the age of the collisional orogeny in the Aravalli-Delhi Mobile Belt was deduced using electron microprobe (EMP) dating of monazites of two suites of metapelitic to metapsammitic rocks from the Banded Gneissic Complex of Central Rajasthan.
146 citations
TL;DR: In this article, the authors evaluate the possibility that the Khanka/Jiamusi/Bureya block may have originated in Siberia and once formed part of the Sayan-Baikal orogen at ∼500 ǫ.
145 citations
TL;DR: The existence of high pressure metamorphic rocks such as eclogite in Archean cratons has been used to argue that plate tectonics did not operate until Earth had cooled to a critical point as mentioned in this paper.
Abstract: The nature of tectonic processes on the early Earth is still controversial. The scarcity of high-pressure metamorphic rocks such as eclogite (the high-pressure equivalent of basalt) in Archean cratons has been used to argue that plate tectonics did not operate until Earth had cooled to a critical point, perhaps around the 2.5 Ga Archean-Proterozoic transition. However, eclogites occur as meter- to kilometer-sized lenses enclosed in Archean gneisses of the Belomorian Province of the Fennoscandian shield. Geochemistry and internal features suggest that the protoliths of the eclogites were interlayered olivine gabbros, troctolites, and Fe-Ti oxide gabbros. Greenschist facies mineral parageneses are enclosed in prograde-zoned eclogite garnets, and peak metamorphic conditions define an apparent thermal gradient (12–15 °C/km), consistent with metamorphism in a warm Archean subduction zone. We show here that these eclogites represent the oldest known high-pressure metamorphic rocks. U-Pb dating and Hf isotope analyses of zircons from the eclogites and a crosscutting felsic vein define a minimum age of 2.87 Ga for the Uzkaya Salma eclogite; a 2.70 Ga age for the Shirokaya Salma eclogite is interpreted as the age of a granulite facies overprint. Thermal overprinting and growth of new zircon also occurred during the Svecofennian (1.9–1.8 Ga) orogeny. These new data imply that plate tectonic processes operated at least locally in late Mesoarchean time. The adakitic nature of the felsic vein suggests that partial melting of hydrated eclogites could produce Archean tonalite-trondhjemite-granodiorite–type magmas.
132 citations
TL;DR: The timing and extent of polymetamorphism in the Mangalwar and Sandmata Complexes from the Aravalli-Delhi Orogenic Belt of Rajasthan (NW India) remains contentious.
129 citations
TL;DR: The concept of paired metamorphic belts was introduced by Brown et al. as mentioned in this paper, which is used in the context of the relationship between thermal regimes and tectonic settings, and is particularly useful in subduction-to-collision orogenic systems.
128 citations
TL;DR: The Khanka Massif is a crustal block located along the eastern margin of the Central Asian Orogenic Belt (CAOB) and bordered to the east by Late Jurassic-Early Cretaceous accretionary complexes of the Eastern Asian continental margin this paper.
Abstract: The Khanka Massif is a crustal block located along the eastern margin of the Central Asian Orogenic Belt (CAOB) and bordered to the east by Late Jurassic–Early Cretaceous circum-Pacific accretionary complexes of the Eastern Asian continental margin. It consists of graphite-, sillimanite- and cordierite-bearing gneisses, carbonates and felsic paragneisses, in association with various orthogneisses. Metamorphic zircons from a sillimanite gneiss from the Hutou complex yield a weighted mean 206Pb/238U age of 490 ± 4 Ma, whereas detrital zircons from the same sample give ages from 934–610 Ma. Magmatic zircon cores in two garnet-bearing granite gneiss samples, also collected from the Hutou complex, yield weighted mean 206Pb/238U ages of 522 ± 5 Ma and 515 ± 8 Ma, whereas their metamorphic rims record 206Pb/238U ages of 510–500 Ma. These data indicate that the Hutou complex in the Khanka Massif records early Palaeozoic magmatic and metamorphic events, identical in age to those in the Mashan Complex of the Jiamusi Massif to the west. The older zircon populations in the sillimanite gneiss indicate derivation from Neoproterozoic sources, as do similar rocks in the Jiamusi Massif. These data confirm that the Khanka Massif has a close affinity with other major components of the CAOB to the west of the Dun-Mi Fault. Based on these results and previously published data, the Khanka Massif is therefore confirmed as having formed a single crustal entity with the Jiamusi (and possibly the Bureya) massif since Neoproterozoic time.
112 citations
TL;DR: In this paper, the authors presented 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 HREE-depleted intrusive rocks intruding the granitoid in the Lhasa terrane.
TL;DR: In this article, the authors presented a trace element analysis of metamorphic zircons from the Trans-North China Orogen (TNCO) and showed that they were mainly derived from the TNCO with some possibly derived from continental rocks of the North China Craton.
Journal Article•
TL;DR: Recently, high pressure pelitic granulite with typical mineral assemblage of garnet+kyanite+perthite were discovered in the Helanshan khondalite series as mentioned in this paper.
Abstract: The khondalite series in Helanshan region is a main part of the khondalite belt in the western block of the North China Craton,the metamorphic evolution of which is still ambiguous.Recently,high pressure pelitic granulite with typical mineral assemblage of garnet+kyanite+perthite were discovered in the Helanshan khondalite series.Petrographic observation and phase modeling indicate that the pelitic granulite experienced four stages of metamorphism.An early prograde metamorphic stage(M1)was recognized from inclusions of biotite and muscovite in garnet.The peak metamorphic stage(M2)is characterized by the presence of garnet+kyanite+perthite,with a probable PT condition of 1.4~1.5GPa at ca.850~870℃.The post-peak decompression(M3)is indicative of an isothermally overprinting of sillimanite and cordierite from kyanite and garnet with pressures of 0.6~0.8 GPa at ca.840~860℃.Development of most biotite suggested a late-stage retrogression(M4)under PT conditions of 780~810℃,0.45~0.55GPa.This clock-wise P-T path,characteristic of a post-peak isothermal decompression(ITD)and followed by cooling,is consistent with a thinning process of thickened continental crust which may be a result of the collision between the Yinshan block and Ordos block.
TL;DR: The ophiolitic melange of the Sabzevar Range (northern Iran) is a remnant of the Mesozoic oceanic basins on the northern margin of the Neotethys that were consumed during the Arabia-Eurasia convergence history as mentioned in this paper.
Abstract: Terra Nova, 22, 26–34, 2010
Abstract
The ophiolitic melange of the Sabzevar Range (northern Iran) is a remnant of the Mesozoic oceanic basins on the northern margin of the Neotethys that were consumed during the Arabia–Eurasia convergence history. Occurrence of km-scale, dismembered mafic HP granulitic slices is reported in this study. Granulites record an episode of amphibole-dehydratation melting and felsic (tonalite/throndhjemite) melt segregation at c. 1.1 GPa and 800 °C. In situ U(-Th)–Pb geochronology of zircon and titanite grains hosted in melt segregations points to an Early Cretaceous (Albian) age for the metamorphic climax. Results of this study (i) impose reconsideration of the current palaeotectonic models of the Neothetyan convergent margin during the Early Cretaceous and (ii) argue that punctuated events of subduction of short-lived back-arc oceanic basins accompanied the long-lasting history of the Neotethyan subduction in the region.
TL;DR: In this paper, the identification of major Grenville-age tectonomagmatic events and their timing in the Western Sierras Pampeanas has been investigated using geochemical and isotope analysis.
TL;DR: The South Delhi Terrane of the Aravalli-Bundelkhand Protocontinent of India has been studied in this article, where the granulite facies metamorphism is marked by a spinelcordierite-garnet-sillimanite-quartz assemblage with melt phase.
TL;DR: Garnet geochronology was used to provide the first direct measurement of the timing of eclogitization in the central Himalaya as discussed by the authors, and the results indicated that Lu-Hf dates from garnet amphibolites from the Arun River Valley in eastern Nepal indicate an age of 20.7 ± 0.4.
TL;DR: In this article, high-resolution ion-microprobe data reveal a complex pattern of zircon ages distributed along the concordia curve between the time of granulite facies metamorphism at c. 2.89 Ga and 3.04 Ga.
Abstract: Zircons from two granulite facies gneisses from the central region of the Lewisian Complex have been investigated by high spatial resolution ion-microprobe U–Pb dating and laser ablation combined Pb–Hf isotope methods. The ion-microprobe data reveal a complex pattern of zircon ages distributed along the concordia curve between the time of granulite facies metamorphism at c. 2.5 Ga and the oldest zircon in each sample (respectively 2.89 Ga and 3.04 Ga). This Pb-loss pattern complicates assignment of an unambiguous magmatic protolith age to the zircon although cathodoluminescence (CL) imaging is used to suggest a preferred age of c. 2.85 Ga for both samples, with older grains being inherited. In situ Hf isotopes show a larger spread in the sample containing older grains which is also consistent with inheritance and further suggests that several crust extraction events are represented in the inherited population. Comparison of Hf isotope compositions with plausible model evolution curves suggests that crustal precursors to the Lewisian granulites were derived from their mantle source at c. 3.05–3.2 Ga.
TL;DR: In this paper, a revised Ti-in-zircon geothermometer was applied to Paleoproterozoic ultra-high-temperature (UHT) granulites at Tuguiwula, Inner Mongolia, North China Craton.
Abstract: The revised titanium-in-zircon geothermometer was applied to Paleoproterozoic ultrahigh-temperature (UHT) granulites at Tuguiwula, Inner Mongolia, North China Craton. The Tuguiwula granulites contain diagnostic UHT mineral assemblages such as sapphirine + quartz and high alumina orthopyroxene + sillimanite + quartz, suggesting formation under temperatures of ca. 1,000°C and pressures of up to 10 kbar. Here, we report detailed petrographic studies and ICP-MS data on titanium concentration in zircons associated with the UHT assemblages. The zircons associated with sapphirine–spinel–sillimanite–magnetite assemblages have the highest Ti concentration of up to 57 ppm, yielding a temperature of 941°C, and suggesting that the growth of zircons occurred under ultrahigh-temperature conditions. The maximum temperatures obtained by the revised Ti-in-zircon geothermometer is lower than the equilibrium temperature of sapphirine + quartz, indicating an interval of cooling history of the granulites from UHT condition to ca. 940°C. Many of the zircons have Ti concentrations ranging from 10 to 33 ppm, indicating their growth or recrystallization under lower temperatures of ca. 745–870°C. These zircons are interpreted to have recrystallized during the retrograde stage indicated by microstructures such as cordierite rim or corona between spinel and quartz, and orthopyroxene–cordierite symplectite around garnet. Previous geochronological study on the zircons of the Tuguiwula UHT granulites gave a mean U–Pb SHRIMP age of 1.92 Ga. However, based on the Ti-in-zircon geothermometer results reported in this work, and considering the relatively slow thermal relaxation of these rocks, we infer that the timing of peak UHT metamorphism in the Tuguiwula area could be slightly older than 1.92 Ga.
TL;DR: In this paper, the ages of the UHT granulites of the central Highland Complex, Sri Lanka, have been studied and dates of ca. 2.5-0.83 Ga have been obtained.
Abstract: Ultrahigh-temperature (UHT) granulites of the central Highland Complex, Sri Lanka, underwent some of the highest known peak temperatures of crustal metamorphism. Zircon and monazite U-Pb systems in granulites near Kandy, the highest grade region (∼1050 °C; 0.9 GPa), preserve both a record of the timing of prograde and retrograde phases of UHT metamorphism and evidence for the ages of older protolith components. Zircon grains from a quartz-saturated granulite containing relics of the peak UHT assemblage have remnant detrital cores with dates of ca. 2.5–0.83 Ga. Date clusters of ca. 1.7 and 1.04–0.83 Ga record episodes of zircon growth in the source region of the protolith sediment. Two generations of overgrowths with contrasting Th/U record metamorphic zircon growth at 569 ± 5 and 551 ± 7 Ma, probably in the absence and presence of monazite, respectively. The age of coexisting metamorphic monazite (547 ± 7 Ma) is indistinguishable from that of the younger, low-Th/U zircon overgrowths. Zircon from a quartz-undersaturated monazite-absent UHT granulite with a mainly retrograde assemblage is mostly metamorphic (551 ± 5 Ma). The ca. 570 Ma zircon overgrowths in the quartz-saturated granulite probably record partial melting just before or at the metamorphic peak. The ca. 550 Ma zircon in both rocks, and the ca. 550 Ma monazite in the quartz-saturated sample, record post-peak isothermal decompression. A possible model for this pressure-temperature-time evolution is ultrahot collisional orogeny during the assembly of Gondwana, locally superheated by basaltic underplating, followed by fast extensional exhumation.
TL;DR: Combined U-Pb ages and Lu-Hf isotope systematics of individual zircon grains from lower crustal rocks of late Mesoproterozoic (Grenville) age, reveal a long geologic evolution of the Oaxaquia terrane of E and S Mexico as mentioned in this paper.
TL;DR: In this article, the authors investigated several mineral phases and their replacement products which occur as inclusions in garnets from felsic and mafic granulites of the Gfohl Unit in the Moldanubian Zone.
TL;DR: The character of mountain building processes in Palaeoproterozoic times is subject to much debate as discussed by the authors, based on the discovery of high pressure granulites in the Man Rise (Cote dIvoire), several authors have argued that Eburnean reworking of the Archean basement was achieved by modern-style thrust-dominated tectonics.
Abstract: The character of mountain building processes in Palaeoproterozoic times is subject to much debate. Based on the discovery of high-pressure granulites in the Man Rise (Cote dIvoire), several authors have argued that Eburnean (Palaeoproterozoic) reworking of the Archean basement was achieved by modern-style thrust-dominated tectonics. A mafic granulite of the Kouibli area (Archean part of the Man Rise, western Ivory Coast) displays a primary assemblage (M1) containing garnet, diopsidic clinopyroxene, red-brown pargasitic amphibole, plagioclase (andesine), rutile, ilmenite and quartz. This assemblage is associated with a subvertical regional foliation. Symplectites that developed at the expense of the M1 assemblage contain ortho- pyroxene, clinopyroxene, plagioclase (bytownite), green pargasitic amphibole, ilmenite and magnetite (M2). Multiequilibrium thermobarometric calculations and P-T pseudosections calculated with THERMOCALC suggest granulite facies conditions of � 13 kbar, 850 � C and <7 kbar, 700-800 � C for M1 and M2, respectively. In agreement with the qualitative information obtained from reaction textures and chemical zoning of minerals, this suggests an evolution dominated by decompression accompanied by moderate cooling. A Sm-Nd garnet - whole-rock age of 2.03 Ga determined on this sample indicates that this evolution occurred during the Palaeoproterozoic. It is argued that from the geodynamic point of view the observed features are best explained by homogeneous thickening of the margin of the Archean craton, re-heated and softened due to the accretion of hot, juvenile Palaeoproterozoic crust, as well as coeval intrusion of juvenile magmas. Crustal shortening was mainly accommodated by trans- pressive shear zones and by lateral crustal spreading rather than large-scale thrust systems.
TL;DR: In this article, a detailed description on crustal metamorphic signatures of garnet-clinopyroxene-quartz-rutile-bearing high P-T granulites, Samgot unit, Imajingang belt, northwestern Korean Peninsula that formed during Permo-Triassic regional metamorphism related to the amalgamation of East Asian continental fragments.
TL;DR: In this article, the authors performed geochronological, petrological and geochemical studies on granulite xenoliths from a Late Cretaceous basaltic breccia dike in Junan, Shandong province, eastern China.
TL;DR: In this paper, the Andrelândia Nappe System is used to investigate the formation and exhumation of high-pressure granulites related to subduction-collision-extrusion processes.
TL;DR: In situ mineral (garnet, zircon) trace element and garnet-rock REE distribution data obtained on leucogranulites from the Bohemian Massif are consistent with an origin of these now strongly deformed rocks as migmatitic leucoglranites formed through dehydration-melting of muscovite-bearing protoliths at high pressures during the Variscan orogeny.
Abstract: In situ mineral (garnet, zircon) trace element and garnet^rock REE distribution data obtained on leucogranulites from the Bohemian Massif are consistent with an origin of these now strongly deformed rocks as migmatitic leucogranites formed through dehydration-melting of muscovite-bearing protoliths at high pressures during the Variscan orogeny. Partial melting at P^T conditions of 900^9408C and 1·6^1·8 GPa consumed mica and feldspar to produce peritectic kyanite and high-Ca (20^24 mol % grossular), high-Eu garnet along with leucogranitic melt. DREE(Grt/rock) values calculated from this garnet and its host rock are consistent with garnet^melt equilibrium at these P^T conditions. Ternary feldspar and rutile (2000^3200 ppm Zr) crystallized from the leucogranite melts in the migmatites at minimum temperatures of 4880^9208C.These formed along with apatite prior to and accompanying the crystallization of garnet rims and the majority of the garnet that occurs in the leucogranulites. This garnet is typified by strong depletion in Eu and DREE(Grt/rock) values consistent with garnet^melt equilibrium only after the fractionation of apatite (50·3 wt %) and ternary feldspar (5^15 wt %). Zircons in one leucogranulite are dominated by oscillatory-zoned grains that yield pre-Variscan U^Pb ages (495 and 433 Ma) and crystallized, from Ti-in-zircon thermometry, at 700^8108C in their original host magmas. These xenocrystic grains are potentially preserved because of the short timespan of the high P^T Variscan event at 340 Ma and the moderate amounts of leucogranitic partial melt present in the rocks, estimated as at least 30 wt % melt from Zr mass balance.The production of new zircon associated with the Variscan event in this leucogranulite is limited to weakly zoned zircon rims characterized by flat heavy REE patterns that approach REE equilibrium with garnet rims. This post-peak zircon was formed at minimum P^T conditions of 8408C and 0·8^1·0 GPa along the decompression-cooling path defined by previous work for the Bohemian Massif granulites. The garnet^ whole-rock REE relationships, observation of Eu depletion between early and later garnet growth phases, and Zr^Ti thermometric estimates indicating temperatures of48408C for this evolution cannot be explained by the alternative interpretation of the leucogranulites as reworked and recrystallized pre-Variscan low-P granitoids, but support a model in which the Bohemian leucogranulites were high-P Variscan-age migmatites containing significant amounts of melt.
TL;DR: Pembroke granulite from Fiordland, New Zealand provides a window into the mid-to lower crust of magmatic arcs as discussed by the authors, where trace element zoning in large, euhedral garnet is compatible with little post growth modification.
TL;DR: In this article, a set of mineral trace element data obtained by LA-ICP-MS analyses of mafic and intermediate granulites from Central Finland is used for the formulation of a mineral/melt partition coefficient that is applicable for trace element modelling under lower crustal conditions.
Abstract: Analyses of trace elements in the mineral phases of granulites provide important information about the trace element distribution in the lower crust Since granulites are often considered residues of partial melting processes, trace element characteristics of their mineral phases may record mineral/melt equilibria thus giving an opportunity to understand the nature and composition of melts in the lower continental crust This study provides an extensive set of mineral trace element data obtained by LA-ICP-MS analyses of mafic and intermediate granulites from Central Finland Mass balance calculations using the analytical data indicate a pronounced contribution of the accessory minerals apatite for the REE and ilmenite for the HFSE Coherent mineral/mineral ratios between samples point to a close approach to equilibrium except for minerals intergrown with garnet porphyroblasts Mineral trace element data were used for the formulation of a set of D
mineral/melt partition coefficients that is applicable for trace element modelling under lower crustal conditions D
mineral/melt were derived by the application of predictive models and using observed constant mineral/mineral ratios The comparison of the calculated D
mineral/melt with experimental data as well as the relationship between mineral trace element contents and a leucosome with a composition close to an equilibrium melt provides additional constraints on mineral/melt partitioning The D values derived in this study are broadly similar to magmatic partition coefficients for intermediate melt compositions They provide a first coherent set of D values for Sc, V, Cr and Ni between clinopyroxene, amphibole, garnet, orthopyroxene, ilmenite and melt In addition, they emphasize the strong impact that ilmenite exerts on the distribution of Nb and Ta
TL;DR: In this article, the Masang Kang suite of NW Bhutan Himalaya has been investigated for their geochemical and isotopic characteristics in order to determine their protolith history, and the results indicate that the rocks were originally tholeiitic and alkali basalts with minor ultramafics.