Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey

Guangzhou, China

Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey

Guangzhou, China
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Chen G.,Sun Yat Sen University | Chen G.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Wang Y.,Sun Yat Sen University | Chen Z.,Sun Yat Sen University | And 3 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2017

Granite (sensu lato) that belongs to the continental crust is the rock of distinguishing the lithosphere of the earth from that of other planets. Geological evidence from both planetary exploration and ODP constrain the formation of granite: no granite was generated during transition from magmatic surface to rocky shell of the inner planets, and formation of granite and its related continental crust should initiate after the occurrence of sedimentary rocks on the earth' s surface. The average growth rate of granite in 2-D space of the lithosphere is about 485 X 10 km/Myr and magma is considered mainly from the partial melting of crustal rocks (anatexis). On the basis, we introduce the progression in the study of crustal anatexis and the relationship between rheological behaviors and melt fraction of the partially melted rocks, and compare the similarities and differences of the both models, i. e. magma intrusion and the magma convection, on explaining the formation-emplacement mechanism of granitic magma. The magma source and its related granite body are separated in the magma intrusion model. One of the difficulties for the model is that the magma source is located beneath its related granite body and thus used to be unobservable unless the granite body and the rocks between the granite and the source have been moved out by erosion or structure. Finally, we brief the study advance of intra-crustal magma convection. In the convection model, the source and the emplacement place of magma are regarded as a whole. When the melt fraction of the rocks in the source region reaches the solid-liquid transition (SLT), the rocks change into "dirty" magma. Gravitational differentiation within the "dirty" magma layer initiates heat convection that results in moving up of the MI (SLT) and thickening of the crustal magma layer. It is concluded that thermal convection within a crustal melting layer is essential for formation of granite magma; without convection, partial melting generates migmatite, but not magma that forms granite batholiths.

Chen Z.,Jilin University | Chen Z.,Sun Yat Sen University | Chen G.,Sun Yat Sen University | Chen G.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | And 2 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2017

Unobservability of the rock-forming process of granite has resulted in a long-term controversy of granite genesis. Numerical techniques combined with super-computer create the possibility of digital reconstruction of the thermodynamic process of granite formation. Here we first look back the advance in study of physical-chemical parameter of rock-melting, introduce the concept of crustal 'average strength' and re-determine the positions of the known rheological transitions, i. e. the MCT, FMT and SLT on the relationship of crustal average strength vs. melt fraction. Secondly, a review of advance in physical and numerical simulations of the various models of magma emplacement is given, and the un-universal characteristics of digital models constructed on different emplacement modes are discussed, which are mainly ascribed to the separation of source and room of magma in the intrusion model. Finally, we introduce the 2-D numerical simulation of large-scale crustal melting in the Tianhe-2 super-computer on the basis of in-situ melting model by Chen and Grapes (2007), preliminarily reconstructing the thermodynamic process of formation of granite and migmatite. The modeling result indicates that thermal convection within a crustal partial melting region is essential for formation of granite magma; Roof-stopping results in the upward motion of the MI (SLT) and thus thickening the convection magma layer; And prerequisite for development of a crustal magma layer is not a very high temperature, but a sustained energy input to maintain the convection state of the magma system.

Chen Z.,Jilin University | Chen Z.,Sun Yat Sen University | Liu Y.-J.,Jilin University | Chen G.-N.,Sun Yat Sen University | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2017

Integration of the published experimental data of partially melted amphibolite, orthogneiss, granite and aplite reveals the existence of three rapid strength drops of the rock-assemblage at melt fraction around 7%, 21% and 41% respectively. The first and the last drops are equivalent to the well-known 'melt connectivity transition' (MCT) and 'solid to liquid transition' (SLT). The drop at melt fraction around 21% is newly identified and termed as the 'framework-melting transition' (FMT). The FMT is defined as the transition from eutectic quartz-feldspars melting to refractory biotite melting. The three rheological transitions are well constrained by the geological data from the Fuhu profile in Guangdong Province, SE China. This profile is a 15. m high cliff. Rocks exposed on the profile are zoned as mottled, stripped, narrow-banded and wide-banded migmatites and diatexitic granite from the top of the profile downwards. The leucosome proportions of the zones measured on the outcrops combined with the experimental data of the partially melted rocks have significant implications for understanding the role of rheological transitions during crustal melting.The MCT, which corresponds to the boundary between the mottled and the narrow-banded migmatites, suggests the segregation of melt within the partially melted system along with the compaction of matrix. Thus, the MCT is deemed to be the transition of the partially melted system from matrix-supported (melt stored in pore-space) to framework-supported (melt stored in foliation/bedding-space of protolith).The FMT corresponding to the boundary between the narrow- and the wide-banded migmatites denotes the inception of melting of the solid framework. Mechanically, the FMT can be regarded as the transition of the framework from compaction to fusion, and geochemically, the transition from eutectic melting of quartz-feldspars to that of refractory biotite. The increasing melt due to framework-melting after the FMT is basically limited within the solid framework until the melt fraction exceeding the SLT.The SLT is geologically constrained by the in-situ metatexite-diatexite transition that is also termed as Magma Interface (MI). The SLT (MI) represents the upper limit of a crustal magma layer. Because of the downward increasing temperature and melt fraction, there should be no consecutive layer of felsic rock existed in the space between the SLT (MI) and the mafic lower crust except the isolated rock-blocks within the magma layer. © 2017 Elsevier Ltd.

Zhang J.,Sun Yat Sen University | Zhang J.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Chen Z.,Jilin University | Chen G.,Sun Yat Sen University | And 3 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2017

Caledonian migmatite and migmatitic granite are widely distributed in the southern Qinzhou-Hangzhou junction-zone of South China. Determination of formation temperature of the migmatite-migmatitic granite is important for the understanding of thermodynamic condition and magma generation within the crust of South China during Caledonian Orogeny. The Fuhuling Profile that is a cliff by shoreside located at the most south of the Qinzhou-Hangzhou zone crops out different-typed migmatite and migmatitic granite zoned from top of the profile downwards in the order of spotted migmatite, linear migmatite, ribbon migmatite, banded migmatite and migmatitic granite ('dirty' granite). Authors of this paper make image-sampling of the various rocks of profile with camera in the field. The sampling and specimen-treating methods are as follows: fixing a 30 X 30cm square frame on the outcrop of each-typed rocks, taking photo of the rock within the square frame, converting the images into black and white in computer under the same threshold value, and calculating the percentage of the white part that is considered representing the leucosome (melt) of migmatite. Projecting the melting ratios of different-typed rocks obtained with the above methods to the graph plotted with the experimental results of rock (greywacke)-melting by Winkler and von Platen (1961), both of them show in good agreement. Comparing the temperature given by the graph and the rock-types of Fuhuling profile, we can find that formation temperature of the migmatites in the profile is between 630°C and 705°C (at which the 'dirty' magma is formed), and the embedded depth of the profile is about 7km under surface during the melting process. This composite graph mentioned above can be regarded as a 'melting-thermometer' that supplies a new method for determination of formation temperature of migmatite and can be used not only in Fuhuling but also in other places.

Niu J.,Sun Yat Sen University | Niu J.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Zheng Y.,Sun Yat Sen University | Zheng Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | And 4 more authors.
Yanshi Xuebao/Acta Petrologica Sinica | Year: 2017

The Panlong lead-zinc deposit is a large Pb-Zn deposit discovered in recent years. It is located in the Devonian Shanglun Formation, which is in the southern section of Qingzhou bay-Hangzhou bay metallogenic belt. Based on the field and petrographic observation, three metallogenic stages are recognized: 1) The primary sedimentary stage. In this stage, sulfides were preserved with scattered, layered-banded, disseminated, colloidal to metacolloidal, framboidal, and crumple structures; 2) Reworked stage, represented by stockwork, false brecciated, band, miarolitic, globular, metasomatic, pressure structures; 3) The surface oxidation stage. In this contribution, the characteristics of the fluid inclusions locked in barite of the first two ore-forming stages were studied systematically. The ype of fluid inclusions is relatively sample dominated by the liquid (H2O)-rich inclusions, gas-liquid inclusions. The homogenization temperatures of fluid inclusions in primary sedimentary stage are 110.0 to 234. 31 (mean = 147°C), with corresponding salinities of 0.33% to 15.57% NaCleqv (mean =7. 09% NaCleqv). In contrast, the homogenization temperatures of reworked stage range from 107. 9 to 179. 5°C (mean = 139°C), and the calculated salinities are 1. 82% to 21. 24% NaCleqv (mean = 10. 90% NaCleqv). Laser Raman spectroscopic analyses illustrated that the mainly gaseous composition of fluid inclusion is H2O. The characteristics of ore-forming fluids in primary sedimentary stage is consistent with typical SEDEX deposits, while showing similarities with SEDEX or epithermal deposits in the reworkd stage. Taking regional evolution nto consideration simultaneously, the Panlong leadzinc deposit is defined as a reworked SEDEX deposit.

Ma J.,Chinese Research Academy of Environmental Sciences | Zhou Y.,Sun Yat Sen University | Zhou Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey
Journal of Environmental Sciences | Year: 2011

Soil samples from Huizhou and Zhanjiang, China were analyzed for 16 priority poly cyclic aromatic hydrocarbons (PAHs) with harmonized sampling, sample extraction and analysis quantification methods. The concentrations and sources of PAHs in soil samples of the two cities were compared. Almost all of the PAH components were detectable in 103 soil samples. The concentrations of {caret insertion point}PAHs ranged from 35.40 to 534.5 μg/kg in soil samples from Huizhou, and ranged from 9.50 to 6618.00 μg/kg in samples from Zhanjiang. Evident differences of concentrations, compositions and sources of PAHs in soils were observed between the two cities. The average concentrations of individual component and the sum of a group of PAHs in soil samples from Zhanjiang were significantly higher than those in Huizhou (P < 0.05). Phe, Flu, Pyr, Bbf and Baa were the dominant PAH components both in soil samples from Huizhou and Zhanjiang. Except for these five components, Bap, Up, Daa and Bgp were also the dominant PAH components in soil samples from Zhanjiang. Coal combustion and liquid fossil fuel combustion were the same sources of PAHs in the two cities with different contributions, and petroleum played a key role in PAHs release in Zhanjiang. © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

Tang L.,Sun Yat Sen University | Tang L.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Chen H.,Sun Yat Sen University | Song J.,Sun Yat Sen University
Geosciences Journal | Year: 2016

Water molecules are adsorbed onto the surface and interlayer of clay minerals and form a film, which causes that pore pressure diffusion in clayey soils differs from that in granular material. In this paper, adsorbed water is classified into strongly adsorbed water and loosely adsorbed water, which provide a better understanding of the physical mechanisms of the adsorbed water. To investigate the impact of adsorbed water on pore pressure diffusion, a series laboratory tests were conducted, including the uplift pressure test, pore pressure diffusion test and adsorbed water content test. The experimental results implies that strongly adsorbed water can neither flow nor participate in pressure diffusion, but loosely adsorbed water shears at pressure gradients and participates in laminar flow. Therefore, as long as the dense clayey soil contains loosely adsorbed water, the pore pressure change at a local site can diffuse throughout the material. A concept called “loosely adsorbed water index (Ilo) is defined to characterize both the content and physical properties of loosely adsorbed water: (1) when Ilo ≥ 1, the peripheral water molecules of loosely adsorbed water layer essentially behave the same as free water; (2) as Ilo → 0, the physical properties of adsorbed water may evolve from a gel-like state to a solid-like state (strongly adsorbed water). According to the density of clay and the content of adsorbed water, the process of pore pressure diffusion can be divided into three modes: flow channels of free fluid, deformations of the adsorbed water layer and shear motions of the peripheral-adsorbed water molecules. Pore pressure response to additional water pressure strongly depends on the permeability, seepage path and boundary conditions. The time-lag effect of pore pressure diffusion should be considered in applications of effective stress in engineering. © 2016 The Association of Korean Geoscience Societies and Springer-Verlag Berlin Heidelberg

Zhang X.,Sun Yat Sen University | Zhang X.,CAS Guangzhou Institute of Geochemistry | Zhang X.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Cawood P.A.,University of Western Australia | And 7 more authors.
Gondwana Research | Year: 2016

The Kenting Mélange on the Hengchun Peninsula, Taiwan, formed through tectonic shearing of subduction complex lithologies, probably within the plate boundary subduction channel between the Eurasian and Philippine Sea plates, with further deformation and exhumation in the Pliocene-Pleistocene during arc-continent collision. Field relations reveal a structural gradation from normal stratified turbidite sequence (Mutan Formation) through broken formation to highly sheared Kenting Mélange containing allochthonous polygenic blocks. This gradation is consistent with an increase of average vitrinite reflection values from ~. 0.72% in the Mutan Formation through ~. 0.93% in the broken formation to ~. 0.99% in the mélange, suggesting temperatures of at least 140. °C during formation of the Kenting Mélange. Zircons from gabbro in the Kenting Mélange are dated as 25.46. ±. 0.18. Ma, which together with geochemical data constrains the source to South China Sea oceanic lithosphere. In combination with the field relationships, vitrinite reflectance values, microfossil stratigraphy, and offshore geophysical data from S and SE Taiwan, we propose that the Kenting Mélange initially formed at the subduction plate boundary from off-scraped trench deposits. Minor Plio-Pleistocene microfossils (<. 5%) occur within the mélange in proximity to slope basin of equivalent age and were likely sheared into the mélange during out-of-sequence thrusting associated with active arc-continent collision, which in the Hengchun Peninsula commenced after 6.5. Ma. © 2015 International Association for Gondwana Research.

Li H.,CAS Institute of Geology and Geophysics | Li H.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Zhai M.,CAS Institute of Geology and Geophysics | Zhang L.,CAS Institute of Geology and Geophysics | And 10 more authors.
The Scientific World Journal | Year: 2013

The Qinzhou Bay-Hangzhou Bay joint belt is a significant tectonic zone between the Yangtze and Cathaysian plates, where plentiful hydrothermal siliceous rocks are generated. Here, the authors studied the distribution of the siliceous rocks in the whole tectonic zone, which indicated that the tensional setting was facilitating the development of siliceous rocks of hydrothermal genesis. According to the geochemical characteristics, the Neopalaeozoic siliceous rocks in the north segment of the Qinzhou Bay-Hangzhou Bay joint belt denoted its limited width. In comparison, the Neopalaeozoic Qinzhou Bay-Hangzhou Bay joint belt was diverse for its ocean basin in the different segments and possibly had subduction only in the south segment. The ocean basin of the north and middle segments was limited in its width without subduction and possibly existed as a rift trough that was unable to resist the terrigenous input. In the north segment of the Qinzhou Bay-Hangzhou Bay joint belt, the strata of hydrothermal siliceous rocks in Dongxiang copper-polymetallic ore deposit exhibited alternative cycles with the marine volcanic rocks, volcanic tuff, and metal sulphide. These sedimentary systems were formed in different circumstances, whose alternative cycles indicated the release of internal energy in several cycles gradually from strong to weak. © 2013 Hongzhong Li et al.

Zheng Y.,Sun Yat Sen University | Zheng Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Zhou Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | Wang Y.,Guangdong Provincial Key Laboratory of Geological Processes and Mineral Resource Survey | And 4 more authors.
Ore Geology Reviews | Year: 2016

The Hetai goldfield is located in the southern section of the Qinzhou Bay-Hangzhou Bay metallogenic belt (QHMB), South China. Gold mineralization is controlled by NE-trending ductile shear zones. Gold grade is higher at the shear zone centers and decreases sharply away from the shear zones, regardless of the host rock type. Fluid inclusions (FIs) preserved in the auriferous quartz veins have been analyzed to constrain their genesis. Three types of gold mineralization-related FIs, including moderate-salinity aqueous (A-type), low-salinity H2O-CO2 (B-type) and CO2-dominated (C-type), have been newly identified. The measured homogenization temperatures (Th) range from 130°C to 310°C, with two peaks of about 245°C and 170°C. The calculated pressures of FIs range from 50MPa to 170MPa. Immiscibility and CO2 effervescence of fluids may have played an important role in gold precipitation during the ascent of the ore-forming fluids. The Hetai goldfield is a typical example of orogenic gold deposits originating from auriferous metamorphic fluids. © 2014 Elsevier B.V.

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