Thermal Evolution of Organic Matter and Secondary Hydrocarbon Generation from Upper Paleozoic Coal Deposits in Northern China

The metamorphism and hydrocarbon generation from the Upper Paleozoic coal-bearing strata in Northern China have been widely studied by Chinese geologists since the 1990s. Based on a large amount of data of Ro values,combined with geological background,we have systematically analyzed the thermal evolutionary characteristics of or-ganic matter and the stages of hydrocarbon generation from the Permo-Carboniferous coal deposits and discussed the condition of secondary hydrocarbon generation. The distribution range of secondary hydrocarbon generation in North-ern China is thus determined. It is shown that the coal ranks of the Upper Paleozoic coal deposits are higher in the southern and western belts than those in the northern and eastern belts. Really significant secondary hydrocarbon gen-eration is mainly related to the thermal evolution of organic matter during the Himalayan Period. Profitable areas for secondary hydrocarbon generation should be buried at 3000-4000 m up to the present. Maturity of the Permo-Carbon-iferous source rocks is not very high. It is suggested that the Bohai Bay depression is favourable for secondary hydro-carbon generation and has good oil and gas prospects.

Multi-Method Chronometric Constraints on the Thermal Evolution of the Central Tianshan,NW China

The Tianshan orogenic belt is a major part of the southern Central Asian Orogenic Belt（CAOB）,extending from west to east for over 2500 km through Uzbekistan,Tajikistan,Kyrgyzstan and Kazakhstan to Xinjiang in NW China,and contains the record of multi-phase tectonothermal evolution.Till now.

Thermal properties of harzburgite and dunite at 0.8–3 GPa and 300–823 K and implications for the thermal evolution of Tibet

Thermal diffusivity(D)and thermal conductivity(κ)of harzburgite and dunite from Luobusha ophiolite were simultaneously measured up to 3 GPa and 823 K using the transient plane-source method in a multi anvil apparatus.The results show that the values of D andκof both samples systematically decrease with increasing temperature and increase with increasing pressure.By combination of the thermal physical data of rocks and minerals and geophysical constraints,we performed numerical simulation on the thermal evolution of Tibet vary over depth,distance and geologic ages.The present results provide new constraints on occurrence of partial melting and its geophysical significance beneath Tibetan crust.

Thermal Evolution of Plutons and Uplift Process of the Yanshan Orogenic Belt

Abstract: Thermochronological dating was used to study the thermal evolution of the Mesozoic plutons and uplift history of the Yanshan orogenic belt. The results show that the cooling history of the plutons is complicated, corresponding to the inhomogeneous uplift process of the Yanshan orogenic belt. The Panshan granite cooled fast during 226.48–204.95 Ma at a rate of 10.22°C/Ma after its emplacement at a depth of about 10 km, and its fast uplift occurred in about 96–35 Ma at an average rate of 0.115 mm/a. The Wulingshan pluton cooled fast during 132–127.23 Ma at a rate of 94.34°C/Ma, and its rapid uplift occurred in 86–45 Ma at an average rate of 0.186 mm/a. The Yunmengshan granite cooled fast during 143–120.99 Ma at a rate of 19.51°C/Ma, and its rapid uplift occurred in 106–103.95 Ma and 20–0.0 Ma at a rate of 1.06 mm/a and 0.15 mm/a respectively. The Sihetang granite-gneiss uplifted rapidly since 13 Ma at an average rate of 0.256 mm/a. The Badaling granite uplifted rapidly since 6 Ma at an average rate of 0.556 mm/a. The Cenozoic uplift of the Yanshan Mountains can be well correlated to the rifting process of the surrounding basins.

Thermal evolution characteristics of Triassic coal in Chuxiong Basin and its geological significance

Chuxiong Basin in Yunnan is a typical Mesozoic foreland basin which is enriched in widely distributed Triassic coal resources with thick deposits and of important strategic significance. By applying vitrinite reflectance measurement, inclusion thermometry, fission track dating and EASY% Ro numerical simulation, the Triassic coal thermal evolution history of the Chuxiong Basin was analyzed, and the results were concluded. The vitrinite reflectance of Chuxiong Basin is higher in the west and south in general.Vertically, in the east, west, and north of the basin, the vitrinite reflectance increases with increasing depth, and in the northern part, exceptionally high values occur, and there is no significant regularity in the east. The formation of inclusions inside quartz veins in Chuxiong Basin Triassic coal are unrelated with magmatic hydrothermal fluid, and there are multi-phase inclusions formed in three or four sections of tectonic movements. The main heating period(apparent age) of the Triassic coal is concentrated in the late Cenozoic, during which the coal was subjected to repeated thermal disturbance, resulting in a multimodal distribution of the fission track data, which reveals mild burial features of the early stages of the Late Cenozoic. The Triassic coal of Chuxiong Basin has experienced two major temperature increasing processes, which occurred in the early-mid Yanshan and the early Himalayan, respectively. The first hydrocarbon generation period of coal organic matter occurred in the formation stage of the foreland basin, during which the south and west of the basin generated large amounts of hydrocarbon, but little was preserved. The second generation stage in the Early Himalayan had conditions suitable for high gas accumulation, especially in the western and southern regions. The upper Triassic coal is of moderate burial depth and is less affected by the strike-slip effect. There are key areas of Chuxiong Basin oil and gas exploration, such as the Yanfeng Basin in the north-central, Yongren and Yunlong areas.

Tectono-thermal evolution of the Liwan Sag, deepwater area in the Zhujiang River Mouth Basin, northern South China Sea

The Liwan Sag, with an area of 4 000 km-2, is one of the deepwater sags in the Zhujiang River（Pearl River） Mouth Basin, northern South China Sea. Inspired by the exploration success in oil and gas resources in the deepwater sags worldwide, we conducted the thermal modeling to investigate the tectono-thermal history of the Liwan Sag,which has been widely thought to be important to understand tectonic activities as well as hydrocarbon potential of a basin. Using the multi-stage finite stretching model, the tectonic subsidence history and the thermal history have been obtained for 12 artificial wells, which were constructed on basis of one seismic profile newly acquired in the study area. Two stages of rifting during the time periods of 49–33.9 Ma and 33.9–23 Ma can be recognized from the tectonic subsidence pattern, and there are two phases of heating processes corresponding to the rifting.The reconstructed average basal paleo-heat flow values at the end of the rifting events are -70.5 and -94.2 mW/m^2 respectively. Following the heating periods, the study area has undergone a persistent thermal attenuation phase since 23 Ma and the basal heat flow cooled down to -71.8–82.5 mW/m^2 at present.

Electrical and thermal conductivity of Earth's core and its thermal evolution——A review

The Earth’s core is composed of iron,nickel,and a small amount of light elements(e.g.,Si,S,O,C,N,H and P).The thermal conductivities of these components dominate the adiabatic heat flow in the core,which is highly correlated to geodynamo.Here we review a large number of studies on the electrical and thermal conductivity of iron and iron alloys and discuss their implications on the thermal evolution of the Earth’s core.In summary,we suggest that the Wiedemann-Franz law,commonly used to convert the electrical resistivity to thermal conductivity for metals and alloys,should be cautiously applied under extremely high pressure-temperature(P-T)conditions(e.g.,Earth’s core)because the Lorentz number may be P-T dependent.To date,the discrepancy in the thermal conductivity of iron and iron alloys remains between those from the resistivity measurements and the thermal diffusivity modeling,where the former is systematically larger.Recent studies reconcile the electrical resistivity by first-principles calculation and direct measurements,and this is a good start in resolving this discrepancy.Due to an overall higher thermal conductivity than previously thought,the inner core age is presently constrained at~1.0 Ga.However,light elements in the core would likely lower the thermal conductivity and prolong the crystallization of the inner core.Meanwhile,whether thermal convection can power the dynamo before the inner core formation depends on the amounts of the proper light elements in the core.More works are needed to establish the thermal evolution model of the core.

Formation,evolution,reconstruction of black shales and their influence on shale oil and gas resource

Black shales are important products of material cycling and energy exchange among the lithosphere,atmosphere,hydrosphere,and biosphere.They are widely distributed throughout geological history and provide essential energy and mineral resources for the development of human society.They also record the evolution process of the earth and improve the understanding of the earth.This review focuses on the diagenesis and formation mechanisms of black shales sedimentation,composition,evolution,and reconstruction,which have had a significant impact on the formation and enrichment of shale oil and gas.In terms of sedimentary environment,black shales can be classified into three types:Marine,terrestrial,and marine-terrestrial transitional facies.The formation processes include mechanisms such as eolian input,hypopycnal flow,gravity-driven and offshore bottom currents.From a geological perspective,the formation of black shales is often closely related to global or regional major geological events.The enrichment of organic matter is generally the result of the interaction and coupling of several factors such as primary productivity,water redox condition,and sedimentation rate.In terms of evolution,black shales have undergone diagenetic evolution of inorganic minerals,thermal evolution of organic matter and hydrocarbon generation,interactions between organic matter and inorganic minerals,and pore evolution.In terms of reconstruction,the effects of fold deformation,uplift and erosion,and fracturing have changed the stress state of black shale reservoirs,thereby having a significant impact on the pore structure.Fluid activity promotes the formation of veins,and have changed the material composition,stress structure,and reservoir properties of black shales.Regarding resource effects,the deposition of black shales is fundamental for shale oil and gas resources,the evolution of black shales promotes the shale oil and gas formation and storage,and the reconstruction of black shales would have caused the heterogeneous distribution of oil and gas in shales.Exploring the formation mechanisms and interactions of black shales at different scales is a key to in-depth research on shale formation and evolution,as well as the key to revealing the mechanism controlling shale oil and gas accumulation.The present records can reveal how these processes worked in geological history,and improve our understanding of the coupling mechanisms among regional geological events,black shales evolution,and shale oil and gas formation and enrichment.

Evidence of Thermal Evolution History of Northeast Sichuan Basin-(U-Th)/He Low Temperature Thermochronometry of Apatite and Zircon

（U-Th）/He dating is a newly developed low temperature thermochronometry, and it elaborately reflects cooling history of geologic body under low temperature. It can be applied to analyze thermal evolution of the sedimentary basin, combining with vitrinite reflectance and fission track. （U-Th）/He dating of apatite and zircon from drilling cores in Puguang （普光）-Maoba （毛坝） area and outcrops in Tongjiang （通江） area indicates that the Northeast Sichuan （四川） basin underwent great uplift and denudation during the Tertiary and the Quaternary. During the period, denudation rates changed from 74.8 to 172.5 m/Ma and denudation thickness was between 2 800 and 3 000 m, geotemperature gradually declined into the current temperature, passing through helium closure temperature of apatite. The uplift and denudation relate to new tectonic movement response in the Sichuan basin aroused by the Qinghai （青海）-Tibet plateau. Drilling samples above 4 000 m did not undergo closure temperature of zircon, but the samples nearly 4 000 m might approach closure temperature of zircon and all the samples underwent closure temperature of apatite. According to （U-Th）/He ages of zircon, it is concluded that the Northeast Sichuan basin began to uplift in the Late Jurassic. From the Late Jurassic to the Paleogene, Northeast Sichuan basin was in slow uplift and denudation, but the denudation of Puguang-Maoba area was earlier than that of Tongjiang area. （U-Th）/He ages of zircon indicate the denudation time of provenance areas. On the basis of paleodrainage characteristics, provenance transport and other related data, provenance areas of the clastie rocks are decided, which is worthy to be investigated further.

Thermal evolution effects on the properties of converting Cs-polluted soil into pollucite-base glass-ceramics for radioactive cesium immobilization

The Fukushima nuclear accident in Japan on March 11,2011,produced large amounts of Cs-polluted soil which must be controlled to prevent the spread of hazardous Cs into the environment.In this paper,the effects of heat treatment on the structure and properties of Cs-containing glass-ceramics,as a simulated nuclear waste form,were systematically investigated.Cesium atoms are chemically bonded in the pollucite structure,and the amorphous phase further encapsulates the pollucite crystals in the glassceramics,thus providing an extra protective layer for the immobilized Cs.XRD analysis,Raman and FT-IR studies on the glass-ceramics synergistically indicated that the optimum crystallization temperature for pollucite is around 1000℃.The pollucite is predominantly the main crystalline phase with a narrow crystal size distribution between 0.5 and 2 mm.Standard leaching test results show that the leaching rate of Cs was very low(3.0×10^(-3) g/(m^(2)·d)).The study offers a practical method for immobilizing Cs in pollucite-base glass-ceramics.Moreover,the experimentally obtained data may provide some important references for converting Cs-polluted soil into pollucite-base glass-ceramics waste form.

Rotational energy conversion and thermal evolution of neutron stars

Pulsars are rapidly spinning, strongly magnetized neutron stars. Their electromagnetic dipole radiation is usually assumed to be at the expense of the rotational energy. In this work, we consider a new channel through which rotational energy could be radiated away directly via neutrinos. With this new energy conversion channel, we can improve the chemical heating mechanism that originates in the deviation from β equilibrium due to spin-down compression. The improved chemical and thermal evolution equations with different magnetic field strengths are solved numerically. The results show that the new energy conversion channel could raise the surface temperature of neutron stars, especially for weak field stars at later stages of their evolution. Moreover, our results indicate that the new energy conversion channel induced by the non-equilibrium reaction processes should be taken into account in the study of thermal evolution.

STUDY ON BEHAVIOR OF TRAPPED HYDROGEN IN 18Ni MARAGING STEEL BY THERMAL HYDROGEN EVOLUTION TECHNIQUE

The interaction of hydrogen with interface between the precipitates and the martensitie matrix in 18Ni maraging steel has been studied by means of thermal evolution hydrogen technique us- ing gas chromatograph as hydrogen detector.An evolution rate peak has been observed at 451 K.The height of the peak relates to the amount and distribution of the precipitates.The activation energy for hydrogen escaping from the trap sites is 23.2 kJ/mol.

A great thermal divergence in the mantle beginning 2.5 Ga:Geochemical constraints from greenstone basalts and komatiites

Greenstone basalts and komatiites provide a means to track both mantle composition and magma generation temperature with time. Four types of mantle are characterized from incompatible element distributions in basalts and komatiites： depleted, hydrated, enriched and mantle from which komatiites are derived. Our most important observation is the recognition for the first time of what we refer to as a Great Thermal Divergence within the mantle beginning near the end of the Archean, which we ascribe to thermal and convective evolution. Prior to 2.5 Ga, depleted and enriched mantle have indistinguishable thermal histories, whereas at 2.5-2.0 Ga a divergence in mantle magma generation temperature begins between these two types of mantle. Major and incompatible element distributions and calculated magma generation temperatures suggest that Archean enriched mantle did not come from mantle plumes, but was part of an undifferentiated or well-mixed mantle similar in composition to calculated primitive mantle. During this time, however, high-temperature mantle plumes from dominantly depleted sources gave rise to komatiites and associated basalts. Recycling of oceanic crust into the deep mantle after the Archean may have contributed to enrichment ofTi, A1, Ca and Na in basalts derived from enriched mantle sources. After 2.5 Ga, increases in Mg# in basalts from depleted mantle and decreases in Fe and Mn reflect some combination of growing depletion and cooling of depleted mantle with time. A delay in cooling of depleted mantle until after the Archean probably reflects a combination of greater radiogenic heat sources in the Archean mantle and the propagation of plate tectonics after 3 Ga.

Geological factors controlling deep geothermal anomalies in the Qianjiaying Mine,China

Here,the geological factors controlling deep geothermal anomalies in mines were studied based on the geotemperature,lithologic thermal conductivity,and related geological data collected from the Qianjiaying Mine,China.A simulation of the change in magma waste heat,conducted using the ANSYS Workbench,revealed the distribution characteristics of geothermal anomalies in this mine and the corresponding geological control factors.The results revealed the following points.(1)First-degree heat hazard level(temperature=31-37℃)occurred in the central and southwestern parts of the mine at an^600-m depth,while second-degree heat hazard level(temperature≥37℃)occurred at an^800-m depth.The geotemperature and geothermal gradient in the southwestern part of the mine were anomalously high.(2)The geotemperatures measured in the mine generally reflected a standard increase with depth,while the geothermal gradient remained unchanged with depth.The geothermal gradient and its average value in the study area were 0.70-4.23 and 2.12C·hm^-1,respectively.(3)A combination of stratum characteristics,geological structure,and groundwater characteristics led to geothermal anomalies in mines;additionally,the waste heat from magma had no significant effect on the geothermal field.

Simulation of methane adsorption in diverse organic pores in shale reservoirs with multi-period geological evolution

In shale reservoirs,the organic pores with various structures formed during the thermal evolution of organic matter are the main storage site for adsorbed methane.However,in the process of thermal evolution,the adsorption characteristics of methane in multi type and multi-scale organic matter pores have not been sufficiently studied.In this study,the molecular simulation method was used to study the adsorption characteristics of methane based on the geological conditions of Longmaxi Formation shale reservoir in Sichuan Basin,China.The results show that the characteristics of pore structure will affect the methane adsorption characteristics.The adsorption capacity of slit-pores for methane is much higher than that of cylindrical pores.The groove space inside the pore will change the density distribution of methane molecules in the pore,greatly improve the adsorption capacity of the pore,and increase the pressure sensitivity of the adsorption process.Although the variation of methane adsorption characteristics of different shapes is not consistent with pore size,all pores have the strongest methane adsorption capacity when the pore size is about 2 nm.In addition,the changes of temperature and pressure during the thermal evolution are also important factors to control the methane adsorption characteristics.The pore adsorption capacity first increases and then decreases with the increase of pressure,and increases with the increase of temperature.In the early stage of thermal evolution,pore adsorption capacity is strong and pressure sensitivity is weak;while in the late stage,it is on the contrary.

Tectonic evolution of the Huangling dome and its control effect on shale gas preservation in the north margin of the Yangtze Block, South China

Significant breakthroughs of shale gas exploration have been made in Lower Cambrian and Sinian shale in the north margin of the Yangtze Block,South China.The drill wells with industrial gas flow located in the southern margin of the Huangling dome.Base on the geological survey,2D seismic,geochronological and drill wells data,the tectonic evolution history of Huangling dome was studied,and its control effect on the preservation condition of shale gas was discussed.The result shows that the Huangling dome might undergo four tectonic stages:(1)About 800 Ma,granite intrusion in the Huangling dome basement,primarily of granites replaced metamorphism rocks;(2)800-200 Ma,no significant tectonic movement with slowly buried history;(3)From 200 Ma,multi-phase uplift and the sedimentary rocks was eroded in the core of the Huangling dome.Shale gas in the Cambrian and Sinian strata was well preserved in the margin of the Huangling dome as the following reasons:(1)The Sinian shale was buried about 7.8 km indepth during Middle Jurassic,source rocks have a suitable thermal maturity for shale gas;(2)The rigid basement of the Huangling dome was mainly composed by homogeneity granite,without intensive deformation.As the main challenges of the widely distributed Lower Cambrian and Sinian shale are highmaturity and intensive deformation,a geological unit with a dome probably is a favorable zone for the old age shale gas.Therefore,it indicates that the adjacent zone of the Xuefengshan,Shennongjia and Hannan are the geological units with a dome and probably have potentials for the exploration of shale in the Lower Cambrian and Sinian.

Composition and Evolution of Hydrogen Isotopes of n-Akanes Generated from Anhydrous Pyrolysis of Sediments from Lake Gahai,Gannan,China

To understand the thermal evolution of lacustrine sedimentary n-alkane hydrogen isotopic composition(δD),especially bacterially derived n-alkanes,anhydrous thermal simulation experiments were performed with sediments from Lake Gahai(Gannan,China).We analyzed the original and pyrolysis-generated n-alkanes and theirδD values.The results showed that thermal maturity and n-alkane origins significantly affected the distribution of pyrolysis-generated n-alkanes.In immature to post-mature sediments,the bacterial-derived medium-chain n-alkanes generally had depletedδD values.The maximum difference in averageδD values between the bacterial-and herbaceous plant-derived medium-chain n-alkanes was 32‰,and the maximum difference in δD values among individual n-alkanes was 59‰.We found that the averageδD value of pyrolysis-generated n-alkanes from different latitude was significantly different in immature to highly mature sediments,but similar in post-mature ssediments.The hydrogen isotopes of sedimentary n-alkanes can be used as indicators for paleoclimate/paleo-environment conditions only when sediments are immature to highly mature.During thermal evolution,the δD value of generated individual n-alkanes and the averageδD value increased with thermal maturity,indicating that hydrogen isotopes of sedimentary n-alkanes can be used as an index of organic matter maturity.We established mathematical models of average δD values of generated n-alkanes from immature to post-mature sediments using n C_(21)^(-)/nC_(21)^(+)and average chain lengths.These results improve our understanding of the distribution andδD value of sedimentary n-alkanes derived from herbaceous plants in mid-latitude plateau cold regions.

Influence of deep magma-induced thermal effects on the regional gas outburst risk of coal seams

The thermal effect caused by deep magma intrusion can not only accelerate the metamorphism of coal body,but also bring additional thermal field that changes the mechanical environment of coal seams,thereby affecting the permeability of coal seams.Different from shallow coal resources,deep coal resources are in a mechanical environment characterized by limited stress and strain.Thus,the thermal effect has a more significant influence on the distribution and permeability characteristics of deep coal seams.In this study,the evolution history of highly metamorphic coal seams in Yangquan mining area was analyzed,and the main effect of magmatic activity on coal seams was obtained.Based on the determined vitrinite reflectance data of typical mines in Yangquan mining area,the maximum paleotemperature was calculated by adopting the Barker’s method.Furthermore,the paleotemperature distribution in Yangquan mining area was summarized,and its relationship with the metamorphic degree was acquired.Then,a new permeability model considering the thermal strain was proposed to analyze the permeability evolution in deep coal seams at different ground temperatures.Finally,through a combination of the results of gas pressure and outburst number in Sijiazhuang Mine,Yangquan No.5 Mine and Xinjing Mine,the influence of ground temperature on the gas outburst risk in Yangquan mining area was explored.The following conclusions were drawn:The maximum paleotemperature in Yangquan area can be 303C.In addition,the paleotemperature in the south is higher than that in the north of Yangquan mining area.The various temperatures at different depths bring about different degrees of thermal stress to different coal seams,leading to different strains.Under the fixed displacement boundary conditions in the deep,the coal seam folds and bends to varying degrees.Moreover,the difference in the ground temperature raises the a value of coal seams and lowers the permeability,which promotes the formation of gas-rich zones and increases the risk of coal seam outburst.The research results can help mines to make proper gas disaster prevention plan for different zones.

Genesis of Coal Metamorphism of Late PalaeozoicCoals in the South of North China——A Further Approach to the Effects of ThermalGroundwater on Coal Metamorphism

The close relationship between the genesis of coal metamorphism and the evolution of the regional tectonic framework is expounded on the basis of an analysis of the geological factors causing the metamorphic zonation of the Late Palaeozoic coals in southern North China; in terms of the mechanism for the formation of palaeogeothermal anomalies, the effects of thermal groundwater on coal metamorphism is highlighted and a geological model for thermal groundwater metamorphism of coal established; with the concept of the palaeogeotherm-coal metamorphism system, the genesis of coal metamorphism is analysed according to the distribution pattern of three geological factors: heat source, heat-carrier and channel, and heat-collector.

Thermal Energy of Confined Gravitons can Vary Cold Geodesic Curves

Internal energy of real warm bodies can change their kinetic-potential energy balance on Keplerian orbits and relativistic geodesic. Chiral nature of the mass results in chirality of gravitons and their energy confinement within the constant energy charge of a moving thermodynamical body. Zero energy-momentum gravitons provide dissipative self-heating and spiral fall of massive stars on gravitating centers. Computed self-heating of the pulsar PSR B1913＋16 quantitatively describes its period decay without an outward emission of metric waves in question. Deviation of warm bodies from geodesic trajectories of cold point matter complies with Einstein＇s directives toward pure field physics of material space plenum without metric singularities.