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Upper mantle geotherm for eastern China and its geological implications

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Science China Chemistry 1995年第12期38卷 1482-1492页

作者：徐义刚林传勇史兰斌 J-C.C.Mercier J.V.Ross Laboratoire Petrologiephysique Universite Paris 775252ParisFrance Institute of Geology State Seismological BureauBeijing 100029China Department of Geological Science University of British ColumbiaV6T ZB4VancouverCanada

The equilibrium temperature and pressure of both spinel and garnet peridotite xenolithsfrom eastern China have been estimated by using different geothermobarometers that are currentlyconsidered to be reliable.Based on these data,the upper mantle geotherm for eastern China has beenconstructed.The obtained geotherm is higher than that for old craton regions,but is similar to that for southeasternAustralia.The most prominent feature of the geotherm is that there is a slight gradient at about 60 kmdepth,and the inflection of the geotherm just passes through the transition line between spinel and garnetfacies.It is likely that the inflection represents the botmdary between the lithosphere and asthenosphere.Thestructures of the upper mantle beneath eastern China have also been discussed by combining the results ofpetrologic,rheological and dynamical studies of the upper mantle.

关键词： eastern China upper mantle geotherm mantle xenolith geothermobarometer.

Genetic model and exploration target area of geothermal resources in Hongtang Area, Xiamen, China

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Journal of Groundwater Science and Engineering 2022年第2期10卷 128-137页

作者： Chun-lei Liu Chen-ming Lu Ya-song Li Qi-chen Hao Sheng-wei Cao Institute of Hydrogeology and Environmental Geology Chinese Academy of Geological SciencesShijiazhuang 050061China Fujian Provincial Key Laboratory of Water Cycling and Eco-Geological Processes Xiamen 361000Fujian ProvinceChina

The geothermal resources in Fujian Province are mainly hydrothermal resources of medium-low temperature.To better understand the whole process and conditions of heat control in the middle and deep crust,this study focuses on the analysis of heat accumulation model in Hongtang Area of Xiamen,and the main conditions of the model such as faults and sags are explored and interpreted in detail by using gravity and wide-field electromagnetic methods.4 main faults(F33,F2,F12 and HT-F1)and 10 secondary faults(HT-F2,HT-F3,HT-F4,HT-F5,HT-F6,HT-F7,HT-F8,HT-F9,HT-F10 and HT-F11)were inferred,and the distribution range of sags was delineated.The convective geothermal system is composed of four components:Heat source,geothermal reservoir,heat-conductive fault and heat retaining cover,which form a quaternary heat accumulation model.According to the model,the intersection of the main faults F12,HTF1 and F33 can be delineated as the primary target area of geothermal exploration,while the intersection of the secondary faults(F12 and HT-F6;F12 and HT-F2;HT-F9,HT-F10 and F12;F12 and HT-F11;F33 and HT-F3;HT-F8 and HT-F3;HT-F2,HT-F10 and HT-F1)can be delineated as the secondary target area.Borehole DR01,which is located in the primary target area,shows that the water temperature increases from fast to slow in the depth range of 0–500 m,and stays at 36℃below 500 m.The reliability of the heat accumulation model and the target area was tested via geothermal boreholes,which is of great significance to the exploitation and utilization of geothermal resources in Hongtang Area of Xiamen.

关键词： geotherm Gravity method Wide-field electromagnetic method Target area of geothermal exploration Heat accumulation model Hongtang Area

Thermal State and Strength of the Lithosphere Beneath the Chinese Mainland

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Acta Geologica Sinica(English Edition) 2012年第4期86卷 810-827页

作者： WANG Yang School of Earth Science and Resources China University of Geosciences

The temperature distributions of the lithosphere underneath the mainland of China were estimated by applying local isostatic equilibrium-constrained geothermal calculations. Maps of the lateral temperature variation at depths of 40, 70, and 100 km are presented for the whole Chinese continent, with the thermal thickness of the lithosphere is calculated. Lithospheric roots of 160-200 km thickness underlie Tarim and the Upper Yangtze Korean platform. In general, the Tibetan plateau lithospheres, whereas thinner thermal lithospheres platform, but are absent beneath the entire Sino- and fold belts to the north have warm but thick have been identified in northern Tibet and central Tian Shan around Issyk-Kul Lake. The warm and soft lithosphere in the Tibetan plateau and Tian Shan are caused by uniform north-south shortening, which may represent a snapshot of the early stage of convective thinning of the convergent lithosphere. However, the lithospheric thinning beneath northeastern China might be related to volatile infiltration by dehydration of the deeply subducting Pacific slab during the Cenozoic. Dry and wet upper mantle rheology display ＂jelly sandwich＂ and ＂cr^me brfil^e＂ pictures, respectively, demonstrating the mechanical behaviour of the Chinese lithosphere outside the Tibetan plateau. Considering a more geologically evident wet-mantle rheology, the ＂creme brulee＂ model can approximate the lithospheric rheology for the most earthquake-prone regions on the Chinese mainland.

关键词： geotherm rheology strength continental lithosphere China

Feedforward Neural Network for joint inversion of geophysical data to identify geothermal sweet spots in Gandhar,Gujarat,India

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Energy Geoscience

Energy Geoscience 2021年第3期2卷 189-200页

作者： Apurwa Yadav Kriti Yadav Anirbid Sircar Silver Oak College of Engineering and Technology S.G.RoadGujaratIndia Centre of Excellence for geothermal Energy Pandit Deendayal Petroleum UniversityRaisanGandhinagar382007GujaratIndia DG GERMI and HeadCentre of Excellence for Geothermal EnergyPandit Deendayal Petroleum UniversityRaisanGandhinagar382007GujaratIndia

Artificial Neural Networks(ANNs)are used in numerous engineering and scientific disciplines as an automated approach to resolve a number of problems.However,to build an artificial neural network that is prudent enough to rely on,vast quantities of relevant data have to be fed.In this study,we analysed the scope of artificial neural networks in geothermal reservoir architecture.In particular,we attempted to solve joint inversion problem through Feedforward Neural Network(FNN)technique.In order to identify geothermal sweet spots in the subsurface,an extensive geophysical studies were conducted in Gandhar area of Gujarat,India.The data were acquired along six profile lines for gravity,magnetics and magnetotellurics.Initially low velocity zone was identified using refraction seismic technique in order to set a common datum level for other potential data.The depth of low velocity zone in Gandhar was identified at 11 m.The FNN backpropagation method was applied to gain the global minima of the data space and model space as desired.The input dataset fed to the inversion algorithm in the form of gravity,magnetic susceptibility and resistivity helped to predict the suitable model after network training in multiple steps.The joint inversion of data is conducive to understanding the subsurface geological and lithological features along with probable geothermal sweet spots.The results of this study show the geothermal sweet spots at depth ranging from 200 m to 300 m.The results from our study can be used for targeted zones for geothermal water exploitation.

关键词： Artificial neural network(ANN) geotherm Feedforward neural network(FNN) Geophysics Machine learning(ML)

Heat Shielding Effects in the Earth＇s Crust

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Journal of Earth Science 2017年第1期28卷 161-167页

作者： Yixian Xu Lupei Zhu Qinyan Wang Yinhe Luo Jianghai Xia School of Earth Sciences Zhejiang University Hangzhou 310027 China State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Wuhan 430074 China Hubei Subsurface Multi-Scale lmaging Key Laboratory Institute of Geophysics and Geomatics China University of Geosciences Wuhan 430074 China Department of Earth and Atmospherie Sciences Saint Louis University St. Louis MO 63103 USA School of Earth Sciences China University of Geosciences Wuhan 430074 China

Knowledge of heat flow and associated variations of temperature with depth is crucial for understanding how the Earth functions. Here, we demonstrate possible heat shielding effects that result from the occurrence of mafic intrusions/layers（granulitic rocks） within a dominantly granitic middle crust and/or ultramafic intrusions/layers（peridotitic rocks） within a dominantly granulitic lower crust; heat shielding is a familiar phenomenon in heat engineering and thermal metamaterials. Simple one-dimensional calculations suggest that heat shielding due to the intercalation of granitic, granulitic and peridotitic rocks will increase Moho temperatures substantially. This study may lead to a rethinking of numerous proposed lower crustal processes.

关键词： geotherm crustal laminated structure heat shielding heat conductivity peridotitic in-trusions North Tibet magnetotelluric data.

Thermal State and Structure of the Lithosphere beneath Eastern China: A Synthesis on Basalt-Borne Xenoliths

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Journal of Earth Science 2010年第5期21卷 711-730页

作者：黄小龙徐义刚 Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences

Application of reliable thermobarometer on garnet-bearing mantle xenoliths and granulite xenoliths entrained by Cenozoic basalts in eastern China reveals two main types of geotherm. The first type, as exampled by Hannuoba （汉若坝）, Mingxi （明溪） and probably Northeast China, is characterized by constant slope of data in the P-T space. The second type, as exampled by the high geotherms of Niishan （女山） and probably Xinchang （新昌）, is characterized by variable slopes, with the samples with pressure 〈2 MPa defining a slow slope, whereas the samples with pressure 〉2 MPa define a virtually vertical slope. The different slopes in the second type of geotherm may correspond to different heat transfer mechanisms, with conductive transfer for the shallow upper mantle and advective transfer for the deep mantle. This observed transition in thermal transfer mechanism is consistent with theoretical modeling. The two types of geotherm are not mutually exclusive, because the second type may characterize the thermal state of whole lithospheric section including both mechanical boundary layer （MBL） and thermal boundary layer （TBL）, while the first type may only depict the MBL. The variable geotherms for different regions are indicative of a heterogeneous lithospheric structure in eastern China. （a） Eastern North China craton （NCC） is characterized by a second-type geotherm, corresponding to a thin lithosphere （-70 km）. Comparison of the equilibrium temperatures of spinel peridotites with this geotherm constrains the depth to Moho in eastern North China craton to be 30 kin. In contrast, western NCC （Hannuoba： the first-type geotherm） possesses a relatively low thermal gradient, indicative of a thick lithosphere （〉90-100 km） and a thick crust-mantle transition zone. The dramatic change in crustal and mantle structure across the DTGL （Daxing＇anling （大兴安岭）- Talhangshan （太行山） gravity lineament） is consistent with recent seismic studies. （b） There is a decrease in thermal gradient and in lithospheric thickness from the coast （Xinchang： the sec

关键词： geotherm thermobarometry garnet-bearing peridotite and pyroxenite granulite xenolith lithosphere eastern China.

A preliminary study on the lithospheric thermal structure and rheology of the Tibetan plateau

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Earthquake Science 2012年第5期25卷 399-408页

作者： Yang Wang Division of Petrology School of Earth Sciences and ResourcesChina University of Geosciences

The lithosphere temperature beneath the Tibetan plateau was estimated by local isostasy equilib- rium constrained geothermal calculation. Maps of the lateral temperature variation at depths of 40 km, 70 km, and Moho are presented for the Tibetan plateau, and the thermal thickness of the lithosphere is also presented. The Tibetan plateau has a warm and thick lithospheres, but the thinner lithospheres are identified in the north- ern Tibet and the eastern margin of the plateau. The warm and soft lithospheres in the Tibetan plateau may represent a snapshot of the early stage of convective thinning of the convergent lithosphere. The ＂creme brulee＂ layering demonstrates the rheological behavior of the Tibetan plateau.

关键词： geotherm isostasy rheology lithosphere Tibetan plateau

Seismic Velocity Structure and Composition of the Continental Crust of Eastern China

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Acta Geologica Sinica(English Edition) 2004年第1期78卷 291-297页

作者： WANGYang CAOJiamin ZHUJieshou GuangzhouInstituteofGeochemistry ChineseAcademyofSciencesGuangzhouGuangdong510640 SchoolofEarthSciencesandResources ChinaUniversityofGeosciencesBeijing100083 DepartmentofGeophysics ChengduUniversityofTechnologyChengduSichuan610059

On the basis of a one-by-one latitude-longitude grid three-dimensional seismic velocity model, the crustal P-wave velocity structure in eastern China (105-125°E and 18-41°N) is obtained, and a set of geotherms for each grid is established for P-T correction on P-wave velocities. The average depths of sub-crustal layers and their average P-wave velocities of 18 tectonic units in eastern China are exhibited. Our result presents a 32-34 km thick crust beneath eastern China, which is thinner than previous studies, with an average velocity of 6.54 km/s, corresponding to a 5 kg/m3 variation in crustal mean density. The thicker upper but thinner middle and lower crust results in a lower average seismic velocity of eastern China. An intermediate crustal composition with a SiO2 content of 59.7 wt% has been estimated. However, there exists a significant lateral variation in the crustal structures among the tectonic units of eastern China. The structure and composition features of some regions in eastern China indicate that extension has played an important role in the continental crust evolution of eastern China.

关键词： crustal composition seismic velocity structure geotherm density eastern China

A NEW APPROACH TO IDENTIFY GROUNDWATER ACTIVITY BY USING geothermAL DATA

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Chinese Science Bulletin 1991年第14期36卷 1186-1189页

作者：汪集旸熊亮萍 Institute of Geology Academia Sinica Beijing 100029 PRC

The effect of groundwater activity on the regional geotemperature pattern and heat flow measurements is one of the frontier topics in modem geothermal studies. It is well known that groundwater activity exists everywhere in the uppermost part of the Earth’s crust. However, this activity sometimes seems very difficult to identify during temperature

关键词： groundwater activity geotherm of boreholes reference geothermal gradient observed geothermal gradient.