Paleozoic HP granulite-facies metamorphism and anatexis in the Dulan area of the North Qaidam UHP terrane, western China: Constraints from petrology, zircon U–Pb and amphibole Ar–Ar geochronology

Lithos ◽  
2014 ◽  
Vol 198-199 ◽  
pp. 58-76 ◽  
Author(s):  
Shengyao Yu ◽  
Jianxin Zhang ◽  
C.G. Mattinson ◽  
Pablo García del Real ◽  
Yunshuai Li ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Western China ◽  
Granulite Facies Metamorphism ◽  
The North ◽  
Facies Metamorphism ◽  
North Qaidam ◽  
Ar Geochronology

Late Paleoproterozoic granulite-facies metamorphism in the North Altyn Tagh area, southeastern Tarim craton: Pressure-temperature paths, zircon U-Pb ages, and tectonic implications

2019 ◽  
Vol 131 (9-10) ◽  
pp. 1591-1606 ◽  
Author(s):  
Hailin Wu ◽  
Wenbin Zhu ◽  
Rongfeng Ge
Keyword(s):  
Granulite Facies ◽  
Mineral Chemistry ◽  
Crustal Thickening ◽  
Granulite Facies Metamorphism ◽  
Magmatic Arc ◽  
Collisional Orogen ◽  
The North ◽  
Altyn Tagh ◽  
Facies Metamorphism ◽  
Tarim Craton

Abstract Granulite occupies the root of orogenic belts, and understanding its formation and evolution may provide critical information on orogenic processes. Previous studies have mainly focused on garnet-bearing high-pressure and medium-pressure granulites, whereas the metamorphic evolution and pressure-temperature (P-T) paths of garnet-absent, low-pressure granulites are more difficult to constrain. Here, we present zircon U-Pb ages and mineral chemistry for a suite of newly discovered two-pyroxene granulites in the North Altyn Tagh area, southeastern Tarim craton, northwestern China. Conventional geothermobarometry and phase equilibrium modeling revealed that these rocks experienced a peak granulite-facies metamorphism at T = 790–890 °C and P = 8–11 kbar. The mineral compositions and retrograde symplectites record a clockwise cooling and exhumation path, possibly involving near-isothermal decompression followed by near-isobaric cooling. Zircon U-Pb dating yielded a ca. 1.97 Ga metamorphic age, which likely represents the initial cooling age, based on Ti-in-zircon thermometry. Combined with regional geological records, we interpret that these granulites originated from the basement rocks of a late Paleoproterozoic magmatic arc that was subsequently involved in a collisional orogen in the southern Tarim craton, presumably related to the assembly of the Columbia/Nuna supercontinent. The clockwise P-T paths of the granulites record crustal thickening and burial followed by crustal thinning and exhumation in the upper plate of the collisional orogen. Our data indicate that the initial exhumation of this orogen probably occurred no later than ca. 1.97 Ga, which is supported by widespread 1.93–1.85 Ga postorogenic magmatism in this area.

Arc-related peridotite blocks exhumed to the Eastern Block of the North China Craton prior to 2.47 Ga

2021 ◽  
pp. 1-24
Author(s):  
Mingyue Gong ◽  
Wei Tian ◽  
Zhuang Li ◽  
Bin Fu ◽  
Chunjing Wei
Keyword(s):  
North China Craton ◽  
North China ◽  
Mantle Wedge ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Melt Extraction ◽  
The North ◽  
Mantle Peridotites ◽  
Facies Metamorphism ◽  
Light Rare Earth Elements

Abstract The Songling and Majiayu peridotite blocks occur in the Eastern Block, North China Craton (NCC). Geothermobarometry data show that the Songling peridotites began exhumation from a depth of c. 70 km (c. 23 kbar). During exhumation, the Songling peridotites were intruded by an upper-crust-derived, high-δ18O (up to +7.28‰ in zircon) trondhjemitic dyke at 2.47 Ga and experienced granulite-facies metamorphism. The Songling peridotites have hybrid mantle wedge (HMW) -like high SiO2 (> 45 wt%), high FeOt (c. 10 wt%) content, high modal orthopyroxene abundance (> 35%) and high ϵNd(t) (+18.4 to +21.4), which were generated by the reaction between peridotite and eclogite-derived melts. The clinopyroxenes from the Songling peridotites were in equilibrium with a Nb-, Zr- and Ti-depleted arc-like magma. The Majiayu peridotites are characterized by depletion of Nb, Zr and Hf and are highly enriched in FeOt, Th and light rare earth elements (LREEs), which can be interpreted as an open system reaction between hydrous melts and fore-arc mantle peridotites. These two peridotite blocks are considered to be arc-related mantle peridotites that experienced melt extraction and metasomatism in different styles. They were exhumed to the north margin of the North China Craton during the c. 2.47 Ga arc–continent collision along the Zunhua structural belt.

scholarly journals Supracrustal rocks in the Ammassalik region, South-East Greenland

1989 ◽  
Vol 146 ◽  
pp. 17-22
Author(s):  
R.P Hall ◽  
B Chadwick ◽  
J.C Escher ◽  
V.N Vasudev
Keyword(s):  
Relative Stability ◽  
Granulite Facies ◽  
Ultramafic Rocks ◽  
Granulite Facies Metamorphism ◽  
East Greenland ◽  
Great Thickness ◽  
Metasedimentary Rocks ◽  
The North ◽  
Facies Metamorphism ◽  
Pelitic Rocks

Large belts of supracrustal rocks are abundant in the Ammassalik region of S.E. Greenland, and are referred to collectively as the Siportoq supracrustal association. They comprise overwhelmingly metasediments, mainly of quartz-rich or semipelitic composition, with variable proportions of quartz, kyanite, sillimanite, garnet and biotite. Graphitic schists are also common and marble horizons occur up to a kilometre thick. Garnet amphibolites are volumetrically minor, and ultramafic rocks are extremely rare. Lithological banding representing relict bedding and rare cross-bedding are locally well preserved. The compositions of the metasedimentary rocks suggest that their provenance was dominantly sialic and the great thickness of semi-pelitic rocks suggests that additions of immature minerals kept pace with gentle subsidence of a basin or shelf environment. The thick marble horizons indicate periods of relative stability. Unlike the surrounding quartzo-feldspathic gneisses in the north of the area, the supracrustal rocks do not appear to have undergone granulite facies metamorphism.

scholarly journals Field work on marble and calc-silicate rocks in the Nordre Strømfjord region

1970 ◽  
Vol 28 ◽  
pp. 19-20
Author(s):  
P.B Sørensen
Keyword(s):  
Personal Communication ◽  
Granulite Facies ◽  
Field Work ◽  
Fold Belt ◽  
Granulite Facies Metamorphism ◽  
The North ◽  
Facies Metamorphism ◽  
Basic Rocks ◽  
Metamorphic Gradient ◽  
Silicate Rocks

As a member of the group working in the Agto-Nordre Strømfjord area (see Bondesen, this report) the writer studied and collected from the extensive outcrops of marble and associated calc-silicate rocks which occur in the region, especially around Nordre Strømfjord. Ramberg (1949) divided the Nagssugtoqidian fold belt in this region into the Isortoq Complex and the Egedesminde Complex, the first characterised by granulite facies metamorphism and the latter by amphibolite facies. K. Sørensen (personal communication) has indicated that a metamorphic gradient exists in the Isortoq Complex from the north to the south in the western part of the Agto sheet area, as seen by the increasing amount of orthopyroxene in the basic rocks. The field data obtained on the calcareous rocks can be correlated with this scheme although a detailed study is necessary.

scholarly journals Contrasted types of metamorphism of basic intrusions in the Precambrian basement of the Tasîussaq area, South Greenland

1968 ◽  
Vol 71 ◽  
pp. 1-47
Author(s):  
P.R Dawes
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Precambrian Basement ◽  
Thermal Front ◽  
Granulite Facies Metamorphism ◽  
North West ◽  
Metamorphic History ◽  
Long Span ◽  
The North ◽  
Facies Metamorphism

Metamorphosed rocks of three distinct episodes of basic intrusion can be recognised in the Precambrian basement of the Tasiussaq area, South Greenland. The oldest intrusions, represented by sills and dykes, are pyriclasites and biotitepyriclasites; the second episode intrusions, in the form of dykes, are pyroxenemetadolerites and the third episode intrusions, represented by dykes and small bodies, are metagabbros, metadolerites, metanorites and amphibolites. The metamorphic nature of the rocks of the three episodes is a reflection of age. Chemical and modal analyses of rocks from the three episodes are presented. Fresh diorite sills and dolerite dykes represent later episodes of Precambrian basic intrusion. The basic rocks depict the varying types of metamorphic conditions which affected the area in Precambrian time, and these are seen to differ from the established metamorphic history in areas to the north-west in South Greenland. The pyriclasites and biotite-pyriclasites have been derived through granulite facies metamorphism; the pyroxene-metadolerites by dipsenic metamorphism under conditions corresponding to the amphibolite facies and the metagabbros, metadolerites, metanorites and amphibolites through amphibolitisation during amphibolite facies metamorphism. It is suggested that the metamorphism producing the pyroxene-metadolerites (Sanerutian in age) was controlled by dipsenic conditions inherited from earlier granulite facies metamorphism (Ketilidian in age). This implies that the Ketilidian and Sanerutian metamorphisms in the Tasiussaq area are not separated by a long span of time and that the break in plutonism marked by the pyroxene-metadolerites cannot be regarded as a significant cratogenic hiatus between two separate plutonisms. The importance of water in controlling trends in the metamorphism of dolerites is stressed. The 1st episode intrusions have undergone severe changes since intrusion and no palimpsest features indicative of primary texture or mineralogy remain. The majority of the 2nd episode intrusions display a granular texture, but some display sub-ophitic and relic sub-ophitic textures. The 3rd episode intrusions display a range from ophitic, sub-ophitic and microporphyritic textures to relic stages of these textures. The 1st episode intrusions were emplaced into a geosynclinal pile of sediments and were probably connected with the volcanicity which occurred at the end of sedimentation. The 2nd and 3rd episode intrusions were emplaced into granitic and metamorphic rocks at a later stage in the same 'geological cycle'. Both the 2nd and 3rd episode intrusions are considered to indicate trends in the crust towards brittle conditions marking temporary partial withdrawals of the thermal front. Their preserved ophitic and sub-ophitic textures are not indicative of emplacement and crystallisation in cratogenic conditions.

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