Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China

2000 ◽  
Vol 85 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Chin-Ho Tsai ◽  
Juhn G. Liou
Keyword(s):  
Eastern China ◽  
Ultrahigh Pressure ◽  
The North ◽  
Ultrahigh Pressure Metamorphism ◽  
Eclogite Facies ◽  
Central Eastern ◽  
Dabie Complex

Microdiamonds, their classification and tectonic implications for the host eclogites from the Dabie and Su-Lu regions in central eastern China

2005 ◽  
Vol 69 (4) ◽  
pp. 509-520 ◽  
Author(s):  
Shutong Xu ◽  
Yican Liu ◽  
Guanbao Chen ◽  
Shouyuan Ji ◽  
Pei Ni ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Eastern China ◽  
Dabie Mountains ◽  
Thin Sections ◽  
The North ◽  
First Occurrence ◽  
Metamorphic Terrane ◽  
Central Eastern ◽  
Mixed Types

AbstractWe have found >10 in situ microdiamonds in thin sections of eclogites from the Dabie and Su-Lu regions of central eastern China since the first occurrence of microdiamond in eclogites from the Dabie Mountains (DMT) reported in 1992. The microdiamonds are found not only in the central part but also in the northern part of the DMT. Several free crystals have been recovered from the crushed eclogites from the central DMT. Most in situ microdiamonds are inclusions in garnets but a few larger ones are intergranular. Most of the diamondiferous eclogites in the central part of the DMT are associated with coesite. Most importantly, the observation of microdiamonds in northern Dabie lead us to question the supposition that this is a low-P metamorphic terrane. All the diamondiferous eclogites from both the north and central DMT are of continental affinity as demonstrated by their negative εNd values. Therefore, both the north and central eclogite belts in the DMT are considered to be from the deep subducted terrane. Five in situ microdiamonds and two free crystals are first reported in this paper. The dimensions of the in situ microdiamonds are 30–180 µm and the free crystals are up to 400–700 mm across. All the microdiamonds are confirmed as such by Raman spectroscopy. The results of an infrared spectroscopic investigation on two larger free crystals and two in situ microdiamonds show that all the microdiamonds from both the Dabie and Su-Lu regions are mixed types IaA and IaB diamonds and there is no indication of any synthetic microdiamonds in our samples because such synthetic microdiamonds are always rich in type Ib.

Late Jurassic, high Ba–Sr Linglong granites in the Jiaodong Peninsula, East China: lower crustal melting products in the eastern North China Craton

2017 ◽  
Vol 155 (5) ◽  
pp. 1040-1062 ◽  
Author(s):  
LI-QIANG YANG ◽  
YILDIRIM DILEK ◽  
ZHONG-LIANG WANG ◽  
ROBERTO F. WEINBERG ◽  
YUE LIU
Keyword(s):  
North China Craton ◽  
Late Jurassic ◽  
North China ◽  
Eastern China ◽  
Ultrahigh Pressure ◽  
Granitic Rocks ◽  
Crustal Melting ◽  
Heavy Rare Earth Element ◽  
The North ◽  
Lower Crustal

AbstractThe Jurassic Linglong granites, intrusive into the North China Craton (NCC) in eastern China, provide a critical record of the first major episode of lithospheric-scale extension and magmatism in NE China during Mesozoic time. Our U–Pb zircon dating reveals that the Linglong granites were emplaced during 161–158 Ma, shortly after the inception of a shallow subduction of the Palaeo-Pacific plate beneath East Asia during Middle Jurassic time. These granites have high alkali contents (K2O + Na2O = 8–9 wt%), low MgO and Mg no. values and variable Cr–Ni abundances. Their relatively high Ba and Sr concentrations, relatively low heavy rare Earth element (HREE) and strongly fractionated REE patterns characterize them as high Ba–Sr granites. The negative whole-rock εNd(t) values ranging from −22.4 to −10.9 and wide-ranging zircon εHf(t) values of −39.1 to −1.5 suggest that magmas of the Linglong granites were produced by partial melting of a garnet-amphibolite-bearing lower crust of the Jiaobei Terrane and by re-melting of the Triassic ultrahigh-pressure (UHP) metamorphic rocks and alkaline suites of the Sulu Terrane. The occurrence in the granitic rocks of inherited zircons of the Neoarchaean, Palaeoproterozoic, Neoproterozoic, Palaeozoic and Triassic ages suggests that magmas of the Linglong granites interacted with the ancient crust in these terranes during their ascent. Asthenospheric upwelling, induced by the steepening and rapid rollback of the Palaeo-Pacific slab during Late Jurassic time, provided the heat source for the inferred lower crustal melting. Trench migration and thermal weakening of the crust caused extensional deformation and thinning in the eastern part of the NCC.

scholarly journals Metamorphic Evolution of Garnet-Bearing Ultramafic Rocks in the Hujialin Area, Sulu Ultrahigh-Pressure Orogenic Belt, Eastern China

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 225
Author(s):  
Zeli Wang ◽  
Shukai Zhang ◽  
Xu-Ping Li ◽  
Songjie Wang ◽  
Dan Wang ◽  
...  
Keyword(s):  
Mineral Assemblage ◽  
Eastern China ◽  
Stage Iv ◽  
Mineral Chemistry ◽  
Orogenic Belt ◽  
Ultrahigh Pressure ◽  
Retrograde Metamorphism ◽  
Metamorphic Evolution ◽  
The North ◽  
Convex Upward

The Rizhao Hujialin area is located in the central Sulu ultrahigh-pressure orogenic belt, where garnet clinopyroxenite is exposed in the upper part of an ultramafic rock complex and serpentinized dunite is exposed in its lower part. Based on textural criteria, the garnet clinopyroxenites were divided into three types: Equigranular garnet, porphyroclastic garnet, and megacrystic garnet pyroxenites. The garnet clinopyroxenites have convex-upward chondrite-normalized rare earth element patterns, large positive Pb anomalies, and depletion of high-field-strength elements (e.g., Nb, Zr, and Ti), suggesting a mantle source protolith overprinted by fluid metasomatism. Petrographic, mineral chemistry, phase equilibrium modeling, and zircon U–Pb geochronology data show that the evolutionary stages of the Hujialin garnet clinopyroxenites were as follows: Stage I: formation of the magmatic protoliths; stage II: formation of megacrystic garnet pyroxenite accompanying subduction; stage III: formation of porphyroclastic or equigranular garnet clinopyroxenite with a mineral assemblage of garnet + clinopyroxene + ilmenite + humite accompanying initial exhumation at ~215.0 ± 5.7 Ma; stage IV = progressive cooling and decompression associated with the crystallization of water-bearing minerals such as clinochlore and pargasite at 206 Ma; and Stage V = late epidote amphibolite-facies retrograde metamorphism producing a mineral assemblage of garnet + clinopyroxene + amphibole + chlorite + epidote + ilmenite at ~180–174 Ma associated with fluid activity in shear–tensional fractures and/or pores. The P-T conditions of the peak metamorphism were estimated at 4.5 ± 0.5 GPa and 800 ± 50 °C. Retrograde metamorphism recorded conditions of 1.0 GPa and 710 ± 30 °C during the exhumation and cooling process. The mineral transformation from early high-Al clinopyroxene to garnet and to late diopside records the general metamorphic evolution during subduction and exhumation, respectively. One zircon U–Pb analysis presents the Palaeoproterozoic age of 1817 ± 40 Ma, which is coeval with widespread magmatic and metamorphic events in the North China Craton.

scholarly journals Significant increase of summertime ozone at Mount Tai in Central Eastern China

2016 ◽  
Vol 16 (16) ◽  
pp. 10637-10650 ◽  
Author(s):  
Lei Sun ◽  
Likun Xue ◽  
Tao Wang ◽  
Jian Gao ◽  
Aijun Ding ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Production Efficiency ◽  
North China ◽  
Climate Model ◽  
Eastern China ◽  
Linear Regression Analysis ◽  
Ozone Production ◽  
The North ◽  
Short Period ◽  
Central Eastern

Abstract. Tropospheric ozone (O3) is a trace gas playing important roles in atmospheric chemistry, air quality and climate change. In contrast to North America and Europe, long-term measurements of surface O3 are very limited in China. We compile available O3 observations at Mt. Tai – the highest mountain over the North China Plain – during 2003–2015 and analyze the decadal change of O3 and its sources. A linear regression analysis shows that summertime O3 measured at Mt. Tai has increased significantly by 1.7 ppbv yr−1 for June and 2.1 ppbv yr−1 for the July–August average. The observed increase is supported by a global chemistry-climate model hindcast (GFDL-AM3) with O3 precursor emissions varying from year to year over 1980–2014. Analysis of satellite data indicates that the O3 increase was mainly due to the increased emissions of O3 precursors, in particular volatile organic compounds (VOCs). An important finding is that the emissions of nitrogen oxides (NOx) have diminished since 2011, but the increase of VOCs appears to have enhanced the ozone production efficiency and contributed to the observed O3 increase in central eastern China. We present evidence that controlling NOx alone, in the absence of VOC controls, is not sufficient to reduce regional O3 levels in North China in a short period.

scholarly journals Ultrahigh-pressure metamorphism of crustal rocks from the Rhodope metamorphic province: evidence from coesite, diamond and majoritic garnet in eclogites and metapelites

2001 ◽  
Vol 34 (3) ◽  
pp. 931
Author(s):  
E. MPOSKOS ◽  
D. KOSTOPOULOS
Keyword(s):  
Ultrahigh Pressure ◽  
Majoritic Garnet ◽  
Crustal Rocks ◽  
Laser Raman ◽  
The North ◽  
Ultrahigh Pressure Metamorphism ◽  
The Individual ◽  
Indicator Minerals ◽  
First Time

The Rhodope Metamorphic Province represents an area of continental collision between the Balkan domain to the north and the Pangaeon domain to the south. Today, exposed astride the suture zone are Palaeozoic and Mesozoic protoliths of both continental and oceanic provenance that underwent Alpine deformation and metamorphism in a subduction zone setting. From petrostructural studies the picture that emerged is one of a central, structurally lower, marble-dominated terrain (i.e. a metamorphic core complex), and a surrounding, structurally higher, gneiss-dominated terrain. Here, for the first time, we report the presence of ultrahigh-pressure metamorphic indicator minerals such as coesite, diamond and Si-Ti-Na-P-rich (i.e. majoritic) garnet in amphibolitized eclogites and garnet-biotitekyanite gneisses from localities scattered throughout the structurally higher terrain. These findings, corroborated by optical microscopy, electron microprobe analyses and in situ laser Raman microspectroscopy, suggest that the protoliths of these rocks were dragged down to mantle depths exceeding 200 km. The individual pressure-temperature paths published before for various subunits of the structurally higher terrain should henceforth be regarded as peculiarities of the exhumation path followed by the subunits.

Sign in / Sign up

Export Citation Format

Share Document