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Zhang B.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Yin C.Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Zhang J.J.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wang J.M.,CAS Institute of Geology and Geophysics | And 5 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2017

The Cenozoic Xuelong Shan antiformal dome is located along the northern segment of the Ailao Shan-Red River shear zone in Yunnan, China. Subhorizontal foliation in the gneiss core is recognized, representing a broad top-to-NE shear initiated under amphibolite facies conditions and propagating into greenschist facies in the mantling schist and strike-slip shear zone. Microfabrics of crystallographic-preferred orientations (CPOs) in quartz suggest that the deformation temperatures increased with increasing structural depth from the upper crust (300-500°C) in the mantling schist to the midcrust (15 km or more, ≥650°C) in the gneissic core. This trend is mirrored by variations in the metamorphic grade of the syn-kinematic mineral assemblages and microstructures, which range from garnet+amphibole+biotite+sillimanite+rutile+feldspar in the core to garnet+staurolite+biotite+epidote+muscovite within the limb units. The dome experienced the following deformation history: (1) a broad top-to-NE shear in the subhorizontal foliation of the gneiss core during the first stage of deformation (D1); (2) opposing reverse-sense shear along the two schist limbs of the dome during contraction-related doming (D2-D3); (3) sinistral strike-slip shearing within the eastern limb (D4); and (4) extensional deformation (D5). The structural-thermal patterns suggest the antiformal dome formation was roughly coeval with top-to-NE ductile shearing in the midcrust of Tibet at 32 Ma or earlier. A major implication is that there was a phase of contractional ductile deformation in the region prior to the initiation of strike-slip deformation. © 2017. American Geophysical Union. All Rights Reserved.

Liu X.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Liu X.,Peking University | Ma Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Ma Y.,Peking University | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2017

Coesite (Coe) with grain size in the range of 30-80μm has been synthesized at 5GPa and 1600°C for 12h by using a cubic press. Its unpolarized single-crystal absorption infrared (IR) spectra show 14 IR bands in the range of ∼1200-650cm-1, five of which have high intensity (at ∼1161, 1109, 1063, 1028 and 994cm-1) and are preliminarily assigned to the SiO4 asymmetric stretching (ν 3). In addition, three sharp but relatively weak bands at ∼838, 814 and 796cm-1 are tentatively attributed to the SiO4 asymmetric bending (ν 4). The IR data also show six OH peaks in the range of 3700-3300cm-1, with an estimated H2O content of ∼30(4)wt ppm. Following previous studies, we have assigned the peaks at ∼3464 (#7), 3421 (#8), 3406 (#9) and 3377cm-1 (#10) to the Type-II hydrogarnet substitution, and the peaks at ∼3500 (#6a) and 3534cm-1 (#6b) to the B-based defects, with the latter aroused by possible B contamination in the synthesizing experiments. Annealing experiments conducted consecutively at ∼200, 400, 600, 800, 1000 and 1200°C, with every heating step lasting for 24h, demonstrate that water diffuses quickly out of Coe at T as low as ∼600°C. The material annealed at 1200°C is completely dehydrated and amorphous. A quick response of the water content in Coe to the changes of P, T and composition is thus possible, which may be critical to the preservation of natural Coe in relevant geological processes. It further implies that water in Coe, and possibly in other nominally anhydrous minerals (NAMs), may behave distinctively different from the water located in the hydrous phases such as amphibole and mica, and potentially makes significant contribution to the subduction zone-related fluids. © 2017 Elsevier Ltd.

Wang S.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wang S.,Peking University | Liu X.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Liu X.,Peking University | And 7 more authors.
Physics and Chemistry of Minerals | Year: 2012

Using a conventional high-T furnace, the solid solutions between magnesiochromite and manganochromite, (Mg 1-xMn x)Cr 2O 4 with x = 0.00, 0.19, 0.44, 0.61, 0.77 and 1.00, were synthesized at 1,473 K for 48 h in open air. The ambient powder X-ray diffraction data suggest that the V-x relationship of the spinels does not show significant deviation from the Vegard's law. In situ high-T powder X-ray diffraction measurements were taken up to 1,273 K at ambient pressure. For the investigated temperature range, the unit-cell parameters of the spinels increase smoothly with temperature increment, indicating no sign of cation redistribution between the tetrahedral and octahedral sites. The V-T data were fitted with a polynomial expression for the volumetric thermal expansion coefficient (α T= a 0+a 1T+a 2T -2), which yielded insignificant a 2 values. The effect of the composition on a 0 is adequately described by the equation a 0 = [17.7(8) - 2.4(1) × x] 10 -6 K -1, whereas that on a 1 by the equation a 1 = [8.6(9) + 2.1(11) × x] 10 -9 K -2. © 2011 Springer-Verlag.

Zhang H.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Zhang H.,Peking University | Zhu Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Zhu Y.,Peking University
Ore Geology Reviews | Year: 2016

The Huilvshan gold deposit in the west Junggar (Xinjiang, China) is hosted in chloritized basalts, chlorite-siderite-altered basalts, and quartz-siderite rocks. Our study demonstrated that all these rocks were derived by alteration of basalts in a shear zone. The orebodies, consisting of quartz-sulfide veins and disseminated sulfides, formed in five stages: quartz-muscovite (I), disseminated sulfides (II), quartz-ankerite-sulfide (III), quartz-calcite-sulfide (IV), and quartz-calcite (V). Auriferous minerals are native gold in stage III and electrum in stage IV. During alteration of basalts in the shear zone, ore-forming elements were released from basalts to ore-forming fluid. Compared with fresh basalts, sulfide-bearing chloritized basalts contain much higher Sr, Ba, P, La, Ce, U, Mn, Ni, Zn, As, Ag, and Au contents. Phase analysis of the As-Cu-Fe-S-O system with the SUPCRT92 software package indicates that a decrease of the aH2S value, caused by the fluid-rock reactions and crystallization of sulfides, induced gold precipitation. © 2016 Elsevier B.V.

Zhu Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Zhu Y.,Peking University
Ore Geology Reviews | Year: 2011

This study focuses on zircon U-Pb and muscovite 40Ar/ 39Ar geochronology of gold-bearing mylonitized granite in the north Tianshan of China. All zircon samples have euhedral hydrothermal rims, which have replaced their igneous mantles. Igneous zircon mantles with narrow hydrothermal rims in sample TS06 give a weighted average U-Pb age of 403.7±5.6Ma (1 standard error, MSWD=1.5, n=18). Zircons in TS277 show a complex texture with core (detrital origin, 1276-2215Ma) indicating igneous mantle and a hydrothermal rim. The igneous mantles give a weighted average U-Pb age of 443.4±3.3Ma (MSWD=3.1, n=10). Two younger ages (394 and 400Ma) have been obtained on hydrothermal rims. The mantles plus rims of all zircons have positive εHf (t) values with an average of 3.99±0.86 (MSWD=2.8, n=23). The positive εHf (t) values suggest that the granite magma is derived from melting of juvenile crustal rocks. The shearing deformation post-dated granite intrusion and introduced fluid, which replaced igneous zircons via dissolution and reprecipitation. However, the age data for zircon hydrothermal rims do not represent the time of the dissolution re-precipitation. The zircons crystallized in granite in the Early Silurian (~443Ma) have been replaced on their rims during Middle Triassic deformation (248-238Ma), which was followed by brittle deformation accompanied by gold deposition at ~220Ma, based on 40Ar/ 39Ar dating of muscovite. © 2011 Elsevier B.V.

Huang Q.,Peking University | Huang Q.,The Key Laboratory of Orogenic Belts and Crustal Evolution
Journal of Asian Earth Sciences | Year: 2011

The Ms8.0 Wenchuan earthquake is one of the most catastrophic earthquakes occurred recently. Although the geophysical network around the epicentral region is not dense enough partially due to the inactivity of the Longmenshan fault, the retrospective investigation of geophysical data in and around the epicentral region would be helpful for strengthening the understanding of the seismogenic process of the Wenchuan earthquake. This paper summarized some preliminary results of the retrospective investigation, especially focusing on the seismic and electromagnetic data possibly associated with the Wenchuan earthquake and its aftershocks. The spatio-temporal investigation of the seismicity changes indicated that there is an intermediate-term seismic quiescence around the epicenter during 2006-2007. The electromagnetic data also showed some anomalous changes (including co-seismic electromagnetic changes), which may be related with the Wenchuan earthquake and its aftershocks. Although further work is definitely required to enhance the reliability of the relationship between the above geophysical changes and the seismogenic process, the above preliminary results would provide some useful information for the related study and stimulate further validation study on the precursors of the Wenchuan earthquake. © 2010 Elsevier Ltd.

Wang L.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wang L.,Peking University | Zhu Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Zhu Y.,Peking University
Ore Geology Reviews | Year: 2015

The Hatu, Qi-III, and Qi-V gold deposits in the Hatu-Baobei volcanic-sedimentary basin (west Junggar, Xinjiang) represent the proximal, middle, and distal parts of the Hatu gold district, respectively. Orebodies of these deposits mainly consist of Au-bearing quartz veins and altered host rocks with disseminated sulfide minerals. Six types of pyrite in these mines are studied here to illustrate ore-formation processes. Sedimentary pyrite, including framboidal and fine-grained pyrite, occurs in mudstone-bearing sedimentary rocks or altered volcanic-sedimentary rocks. Framboidal pyrite formed during redox changes in sedimentary layers. Hydrothermal pyrite contains five subgroups, from Py1 to Py5. Porous Py1 formed prior to gold mineralization, and is overgrown by Py2 that contains inclusions of sulfide minerals and native gold. Coarser Py3 coexists with arsenopyrite and native gold, and contains the greatest As concentrations. Gold and antimony are also preferentially concentrated in arsenian Py2 and Py3. The Au-As-deficient Py4 and Py5 formed during the post-ore process. There is a negative correlation between the As and S contents in Py1, Py2, and Py3, implying the substitution of sulfur by arsenic. Gold precipitated under relatively reducing condition in framboid- and graphite-bearing tuffaceous rocks. Cesium, Rb, Sr, La, Ce, Au, As, Sb, Cu, and Pb are concentrated in altered host rocks. The Au-bearing quartz veins and disseminated sulfide mineral orebodies were formed via a co-genetic hydrothermal fluid and formed during different stages. The variation of fO2 during fluid/rock interactions, and crystallization of arsenian pyrite were major factors that controlled gold precipitation. © 2015 Elsevier B.V.

Fan C.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Lu A.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Li Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wang C.,The Key Laboratory of Orogenic Belts and Crustal Evolution
Chemical Engineering Journal | Year: 2010

This paper deals with treating high phenol-concentrated wastewater from coal gasification by manganese oxide method. Mixed-phase manganese oxides of manganite and hausmannite were synthesized with industrial MnSO4 and NaOH by air oxidation. The effects of sulfuric acid dosage, reaction time, temperature, manganese oxide grain size and concentration on removal efficiency of total phenols were studied with laboratory bench-scale experiments. The results indicated that the removal process was more effective under the experimental conditions, i.e. acidified media at pH < 4 and an excessive amount of fine particles with a long reaction time. Solution pH and manganese oxide concentration were two of the most important factors which should be well regulated to guarantee higher removal rate. The mixture of manganite and hausmannite showed improved activity for removal of total phenols, TOC and CODCr as compared with MnO2 (AR) but similar to cryptomelane and K-birnessite. Most of organic contaminants especially phenol which occupied absolute predominance in initial wastewater were removed to enhance the biodegradability for further biological treatment. This investigation will provide fundamental method for developing a pretreatment method of industrial phenolic wastewater with flexibility, simplicity and high activity. © 2010 Elsevier B.V. All rights reserved.

Yang X.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Li Y.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Lu A.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wang H.,The Key Laboratory of Orogenic Belts and Crustal Evolution | And 3 more authors.
Applied Clay Science | Year: 2015

Bacillus mucilaginosus is one of the common soil bacteria and is widely used as a microbial fertilizer to release potassium from K-rich soil minerals. But few researchers have discussed possible effects that the bacteria may have on montmorillonite. This study investigated the effect of B. mucilaginosus strain on the capability of montmorillonite to retain water/cations. After 20days of interaction with B. mucilaginosus D4B1, the expansion ratios of montmorillonite samples decreased from 83.2% to 76.7%, and the cation exchange capacities (CEC) decreased from 80.8 mmol/100g to 67.8 mmol/100g, suggesting the durative interaction with the bacteria may reduce the capabilities of incorporating water molecules and nutrient into the interlayer space of montmorillonite. Morphological changes of discrete layers and etch pits were observed with scanning electron microscope (SEM). In the synchrotron radiation X-ray diffraction (SR-XRD) profiles, the full-width at half maximum (FWHM) of 001 reflection increased to 0.24nm as compared to the abiotic sample (0.19nm), indicating a decreased structural order in bacteria-treated montmorillonite. Also, a new band at 1540cm-1 assigned to asymmetric stretching vibrations of carboxylate was detected by micro fourier-transform infrared spectroscopy (FTIR) in bacteria-treated samples, suggesting the alteration in the mineral structure of montmorillonite was possibly triggered by the organic acids produced by bacteria. Moreover, in bacteria involved dispersion, a significant decrease of the pH value was coupled with a consecutive increase of total protein concentration, indicating the continuous activities of the bacteria during 20days of interaction. Above all, the decreased water-holding or cations-exchange capacity of montmorillonite was related to the partial alteration in the mineral structure of montmorillonite by B. mucilaginosus D4B1. Such a durable interaction on structural alteration of soil clays would have detrimental impact on long-term sustainability of soil resources. © 2015.

Shao J.A.,The Key Laboratory of Orogenic Belts and Crustal Evolution | Wei C.J.,The Key Laboratory of Orogenic Belts and Crustal Evolution
Science China Earth Sciences | Year: 2011

Granulite xenoliths are found in the early Mesozoic diorite intrusions from Chifeng and Ningcheng areas, eastern Inner Mongolia. The granulites are granoblastic and weakly gneissic with mineral assemblage of hypersthene, diopside, plagioclase and minor biotite, amphibole and ilmenite. Some samples contain the intergrowth composed of labradorite and vermicular hypersthene, and some coarse-grained plagioclases of andesine and labradorite composition occasionally develop bytownite rims with vermicular hypersthene, indicating a possible presence of garnet. Presence of blastogabbroic texture and hypersthene with diopside exsolution lamellae in some samples suggests that the protolith of the granulite is norite or gabbro. On the basis of metamorphic research and thermobaric calculation, the evolution of the granulite xenoliths is summarized into the following stages: (1) Isobaric cooling of underplated noritic or gabbroic magma in the lower crust led to the formation of probable garnet-bearing medium-high pressure granulite. (2) These higher pressure granulites were adiabatically uplifted to upper crust by dioritic magma and transformed to low pressure two-pyroxene granulite during an isothermal decompression. (3) The two-pyroxene granulite underwent retrograde metamorphism of different degrees during an isobaric cooling process as a result of crystallization and cooling of the dioritic magma. The pyroxenite-dominated cumulates and the medium-high pressure granulites may have rejuvenated the lower crust during the early Mesozoic. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

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