Abstract:Rift basins in eastern and southern China host abundant oil and gas resources. But the complicated evolution and distribution of the faults are the key issues to be solved in future oil and gas exploration and development. Based on the structure interpretation of a large number of 3D seismic data and the generalized faulting model, this study selected the Nanpu Sag in the Bohai Bay Basin and the Weixinan Sag in the Beibuwan Basin as study examples so as to analyze and summarize the complicated fault system of basins in eastern and southern China. An extension strain ellipse was proposed to predict fault nature in extensional deformation zone. The results show that there are nine ways by which fault system complexity of rift basins in the east-south China are presented. They can be further summarized into three aspects, (1) variety of the fault strike and nature, (2) variable assemblages in the plane and profile, (3) complicated spatiotemporal relation of fault distribution and evolution. The fundamental reasons for complexity of the fault system are the distribution complexity of the preexisting faults and the superposition of extensional deformation in different directions (NWSE and near NS). The evolution of tectonic stress field in different basins and even in different parts of a basin shows great similarities, NWSE extension before 40Ma and northsouth extension since 38Ma. Therefore, the distribution and evolution of faults are mainly affected by the differences in the distribution of preexisting faults.

Abstract:The Liyue basin in the northeast of the southern margin of South China Sea (SCS) experienced complex tectonic evolution in Cenozoic, resulting in the differences of basin structures in different periods. Using abundant 2D seismic data and structural and stratigraphic analysis, this paper studied the evolution and transition process of basin structure, and their response to the complicated dynamic background of the South Sea region. The results show that controlled by the NNE, NEE, NWand nearlyEWtrending fault systems, the Liyue basin is characterized by two depressions (South Depression and North Depression) and one uplift (namely, the Central Uplift). Two regional angular unconformities T70 and T50 unconformities divide into the Cenozoic stratigraphy into three layers, continental rifting layer, drift rifting layer and forelanddepression layer. They responded to a series of reconstruction events of peripheral plates, such as Pacific plate subduction, IndiaEurasia plate collision, new South Sea expansion, ancient South Sea perish, and the Philippine Sea plate wedge, etc. The structural evolution of the Liyue basin experienced three stages, continental episodic rifting stage with the basin structure controlled by NNEand NEEtrending faults and the Southern Depression connected with the Northern Depression; drift rifting stage with the basin controlled by NNEand NWtrending faults and the newly formed Central Uplift separating the Southern Depression from the Northern Depression; forelanddepression stage with the basin shown as a foreland basin structure and quick depression deposition. The characteristics and evolution of basin structure were closely related to the complex dynamic background and recorded the response in the southern margin of SCS to the tectonic events, including the convergence of the Pacific, Eurasian and IndianAustralian plates, the protoSCS subduction, seafloorspreading of SCS and rotation of Philippine Sea Plate.

Abstract:The Yamansu granite pluton consists of 27 intrusive rocks, which can be divided into three lithofacies units but belong to one superunit. The ellipseshaped plutonic body was the product of three intrusive activities of the same magama. Zircon LA-ICP-MS U-Pb dating result shows that the Yamansu pluton intrusion occurred in the Middle Triassic between 227 Ma and 230 Ma and was the product of the Early Indosinnian Period. Zircon insitu Hf isotopic composition analysis of the Yamansu pluton yielded the εHf(t) values between 7.7~11.5 and the two stage Hf mode age (TDM2) varying between 530~776Ma, suggesting that the magma originated from depleted mantle-derived juvenile crustal rock. Geochemically, the pluton is characterized by the high contents of SiO2 (70.73%~78.12%) and K2O+Na2O (7.17%~8.53%), the high ratios of K2O /Na2O (1.1~1.89), and the low contents of Ti, Ca, Fe and Mg, with the ratios of (K2O+Na2O)/Al2O3 varying between 0.75 and 0.91, and the ratios of A/CNK between 0.98 and 1.03. All these features indicate that the pluton belongs to high K calc-alkaline granite. The pluton is enrich in LILE (K, Rb) and HFSE (Th) but depleted in Hf, Zr, Sm, Y and Yb. The chondrite-normalised REE distribution pattern of the Yamansu pluton displayed right skewed shapes, distinct fractionation between LREE and HREE, with slightly negative Eu anomalies (δEu=0.38~0.74). The petrological and geochemical features of the Yamansu pluton indicate that the pluton originated from partial melting of Neoproterozoic new-born crust due to mantle magma intraplating. The magma intrusion was driven by northward subduction and collision of the Tethys Ocean from the Late Hercynian to Early Indosinian, and the subsequent intense intra-continental extention in the East Tianshan Mountains.

Abstract:The sequence division, sedimentary age and provenance of the black clastic rock series called Madian Formation (or Fengtai Formation) between Neoproterozoic and Cambrian dolomites in the southeastern margin of North China Craton (NCC) are still debated. In this study, comprehensive analysis using elemental geochemistry and detrital zircon U-Pb geochronology has provided important evidence for stratigraphic framework and MesoNeoproterozoic to Early Paleozoic tectonic evolution of the southeastern margin of NCC. The enrichment coefficients (EF) of most elements and U-Pb ages of detrital zircons of the whole Madian Formation are similar, and the latter mainly concentrated between 2.6 Ga and 1.0 Ga with multiple age peaks of ~2.5 Ga, ~2.1 Ga, ~1.8 Ga, 1.6~1.4 Ga and 1.3~1.0 Ga. The Madian Formation is generally considered a continuous transgressive stratum of the Cambrian series 2 epoch in the passive continental margin, with sediments entirely derived from the Xuhuai area in the interior of the North China Craton. The Madian Formation is characteristic of two-ends mixing between Neoproterozoic carbonatic sedimentary caprocks and early Precambrian metamorphic basements, manifested by difference of petrology, element geochemistry and provenance. Detrital zircons of >18 Ga were derived from the Early Precambrian metamorphic basement, while the Mesoproterozoic detrital zircons and gravelgrade dolomite debris clastic particles were from the Neoproterozoic sedimentary caprocks, with a very small amount of Neoproterozoic detrital zircons from the Neoproterozoic basic dykes. 1.6~1.4 Ga and 1.3~1.0 Ga detrital zircon records in the Neoproterozoic and lower Paleozoic of the periphery of NCC confirm that a Meso-Neoproterozoic tectonic belt developed at least in the eastern and southern margins of NCC, which are similar to those in the North Qinling region and was strongly involved in the process of Columbia supercontinent breakup and Rodinia supercontinent convergence during the Mesoproterozoic era. The tectonic belt was the main provenance supply area for rift basins in the eastern to southern margin of NCC during early Neoproterozoic era, and started breaking up from NCC at 900Ma so that its provenance proportion has been completely missing in Early Paleozoic Madian formation deposition.

Abstract:The south Ordos basin (S-OB) is located at the west part of the South-sector of North China Block (S-NCB), involved in the multiple orogeny of the North Qinling Belt (NQB) that is composed of the S-NCB to the north and the north Qinling terrain (NQT) to the south. The pre-Ordovician tectonic correlation between the NQT and NCB, as well as the tectonic affinity of the NQT, is still controversial. Here, detrital zircon U-Pb dating analysis of 2-sample sandstones from the neritic-littoral deposits of Nancaode and Zhuanghegou Formations, outcropped in the S-OB, are carried out at the State Key Lab. of Continental Dynamics, China. All the concordant zircons (n=155) from sampled sandstones show broadly similar age patterns with a wide range of 825~2445 Ma. The largest population of zircons exhibits ages of 1659~1935 Ma (n=39) with a peak age at ca.1.86 Ga; and the subordinate populations display ages of 2017~2445 Ma (n=7), 1458~1650 Ma (n=24), 1223~1451 Ma (n=36), 1041~1203 Ma(n=23) and 825~995 Ma (n=13) with the peak ages of ca. 2.09 Ga, 1.59 Ga, 1.33 Ga, 1.12 Ga and 0.83 Ga, respectively. It indicates that the detritus of the the 2-formation deposites were mainly sourced from the metamorphic basement rocks of the NCB and subordinately from the complex and igneous rocks of the NQT. Also, the spectrum of the 2-sample zircon ages, with youngest peak age of 832Ma, is quite similar to that of interlayered sandstones of the late Neoproterozoic (Sinian) tillites exposed in the neighbor study areas of the southwest Ordos basin, but very different from that of sandstones of the Ordovician Pingliang formation outcropped in the S-OB, suggesting the deposit time of the analyzed sample host rocks to be late Neoproterozoic (Sinian) with no more than ca. 0.83 Ga. All of the above reveal that the sedimentary sources of late Neoproterozoic Nancaode and Zhuanghegou Formations are bidirectionally from the NCB and NQT, indicating the NQT was amalgamated to the NCB during the Grenvillian collision to late uplift process. So, it can be supported that the S-NCB amalgamated with NQT as an integrated continental margin developed an extensional sedimentary process after ca. 0.83 Ga, probably corresponding to the Rodinia break-up event.

Abstract:Tieshan complex in Zhenghe, Fujian province has long been regarded as syenite, which is Indosinian alkali intrusive rock uncommonly in South China. This study conducted an investigation for the Shizigang rocks in the south-western area of the Tieshan complex. The results show that their lithology is not common intrusive rock but a metasomatic rock due to strong potassic fluid. The metasomatic rock hosts some residues of protolith, including Indosinian grantic bodies, sandy conglomerate of Early Jurassic Lishan Formation, and volcanic rocks of Early Cretaceous Nanyuan Formation. Therefore, it can be inferred that the metasomatic rock formed in the Cretaceous. K-feldspar of the metasomatic rock occurs in four forms, surfacial potassic alteration, early light colour potassic veins, late dark potassic veins, and melanitepyroxene K-feldspar rock in origin. The first surfacial potassic alteration contains Or of 77.9%~94.3%, Ab of 5.2%~21.3% and An of 0%~0.8%. The second contains Or of 81.5%~91.3%, Ab of 8.2%~17.4%, and An of 0.5%~4.1%. The third contains Or of 91.8%~96.8%, Ab of 3.2%~9.3%, and An of 0.1%~0.4%. The last contains Or of 85.2%~90.0%, Ab of 10.8%~14.6%, and An of 0.2%~0.6%. Potassic metasom atism can be divided into early stage and late stage. X-ray powder diffraction and infrared spectrum analyses show that the early stage metasomatism formed the first two forms of K-feldspar with or dering degree of of 0.71~0.80, structural parameters of 1.27~1.61, triclinicities of 0.23~0.29, and T1(o)+T1(m) of 0.86~0.90; while the late formed the last two forms of K-feldspar with ordering degree of 0.67~0.88, structural parameters of 1.10~1.91, and triclinicities of 0.30~0.70, T1(o)+T1(m) of 0.84~0.93. The first two K-feldspars consist mainly of microclines, especially highly microclines, with crystallization temperatures varying from 200 to 370℃. The types of metasomatic rocks include quartz K-feldspar rock, pyroxene K-feldspar rock and dark garnet K-feldspar rock.

Abstract:A large amount of mafic-ultramafic rocks, which are accompanied with the Toudaogou Formation, occurs in the Toudaogou area, Yongji County, Jilin Province. They have received wide attention from geological industry due to its location near to the Changchun-Yanji tectonic belt. But lacking the high-precision chronology data has greatly restricted the in-depth study of regional tectonic. In this paper, we conducted chronological study for the mafic-ultramafic rocks using zircon U-Pb dating (LA-ICP-MS) method. The study yielded an age of 270±5 Ma for metadiabase and a minimum age of 297 Ma for zircons captured in the metamorphic peridotite. Considering the rock association and their close occurrence, we thought they were both formed in Middle Permian. The zircons captured in the mafic-ultramafic rocks record many important tectonic heat events occurring in the North China Craton and its northern margin. Among them, an age of 446±6 Ma yielded for the metadiabase might indicate the age of magmatic event, and the age of 434±240 Ma for metamorphic peridotite may reflect an important Early Paleozoic tectono-magmatic thermal event in the northern margin of North China Craton. A large number of 1.8~2.4 Ga ages corresponds to the Paleoproterozoic thermal events in Liao-Ji orogenic belt, while 1377 Ma and 1542 Ma corresponds to the era of Jixianian. 869~997 Ma corresponds to the formation era of the Qingbaikouan. In addition, zircons with age of 3.0~3.2 Ga occur commonly in metadiabase. Based on analysis of the age structure and distribution characteristics of the Paleozoic geological bodies in the northern margin of Longgang landmass, this study suggests that there may exist an old metamorphic basement in the study area, and that the exposed mafic-ultramafic rocks formed in the intracontinental tectonic environment, rather than the components of ophiolite. This understanding is of great significance in deepening the research on regional tectonic.

Abstract:The gold-bearing albite-carbonate breccia in the Shuangwang gold deposit is one of typical gold-bearing hydrothermal breccia bodies in the Qinling breccia belt, which is controlled by Fengzhen-Shanyang contemporaneous fault. This paper studied the zircon SHRIMP chronology and petrochemistry, founded that range from sericite slate to albitized slate and albitized breccia, Na2O gradually enriched and K2O gradually depleted, which is a negative correlation,indicating Na brought in and K took out in the ateration process.The formation of albite-carbonate breccia was not a single process but experienced hot-water Sedimentary, single component of hot water with the Syngenetic metasomatism, hydraulic fracturing, hot fluid crypto-explosion, hot fluid boiling, superimposed hydrothermal mineralization, supergenic metallogenesis and other diagenetic mineralization superposition. The range of ages from zircon SHRIMP dating of breccia is large, 423 Ma~513 Ma and 808 Ma~1166 Ma are are two peaks, similar to zircon ages of Devonian sedimentary strata in South Qinling; the youngest zircon ages are 280.1Ma~277.5Ma, representing the lower limit of crypto-explosive breccia.The ore-bearing breccia has experienced three stages: (1) the late devonian, hot water sedimentary in Feng-tai pull-apart basin; (2) during Early-Carboniferous (342Ma), feng-tai basin occured tectonic inversion,and hot alkaline hydrothermal fluid derived from deep earth upwelling,which formed metasomatic alteration and hydraulic breccia;(3) the early-Permian,alkaline carbonate fluid occurred cryptoexplosion and the formed cryptoexplosive breccia. According to the studies, the hydrothermal breccia tectonic system were characteristics of multi-phase and multi-stage superimposed diagenetic.

Abstract:Systemic chronology and petro-geochemistry analysis of Aolaoshan gabbro-diorite was conducted to analyze its genesis, which makes up understanding of tectonic attributes of the northern Qaidam in Late Paleozoic time. Our study shows that the Aolaoshan gabbrodiorite is characterized by high SiO2 and K2O contents, low Na and Al contents, and high Mg#. The primitive mantlenormalized spider diagram shows that the rock is enriched in large ion lithophile elements (Rb, Ba, K) and depleted in high field strength elements (Ta, Nb, Ti and P). The chondritenormalized REE distribution pattern shows a relatively flat, low differentiation curve of LREE and HREE, with low ∑LREE/∑HREE and (La/Yb)N ratios and weak negative to positive Eu anomalies, compared with that of contemporary intermediate-felsic intrusive rocks. SHRIMP U-Pb zircon dating yields an average weighted age of 370.4±3.4 Ma for the gabbro-diorite samples from the Aolaoshan area, which corresponds to Lae Paleozoic magmatic activity. The major and trace element geochemistry analysis illustrates that the rock is of attributes of magmatic rocks formed in islandarc or active continental margin, suggesting that it probably originated from lithosphere mantle contaminated by crust material and metasomatized by fluid in subduction belt. Based on the previous studies on the NeoproterozoicLate Paleozoic oceanic crust subduction and collision between continents tectonic setting, and combined with geochemical tectonic environment discrimination in this study, it can be concluded that the Aolaoshan gabbro-diorite formed in a lithosphere thinning and crustal extension environment resulted from post-orogenic lithosphere delamination, which marks the end of Caledonian orogenesis in the northern margin of Qaidam region.

Abstract:The Fenshuiling Complex is situated in the west of the Malanyu uplift, that is the west of the intrusive rock belt of the central east Hebei Province. U-Pb Zircon Geochronology shows that granodiorite：157.4±2.7Ma，biotite adamellite162.0±4.0Ma，later granodiorite distributed around the early biotite adamellite in a ring belt. It is a typcial complex massif. The granodiorite belongs to the metaluminous high potassium calc-alkaline series,I type granite, SiO2 64.50%~65.56%，(K2O+Na2O) 7.24%~7.70 %,(K2O/Na2O)0.58~0.67，A/CNK 0.91~0.97}.In contrast,the biotite adamellite has a higher content about SiO2and K2O,belongs to peraluminous high potassium calc-alkaline series, I-A type granite {SiO2 73.25%~74.56%， (K2O+Na2O) 7.22%~8.58 %,(K2O/ Na2O) 0.86~1.04; A/CNK 1.09~1.24}.From REE and trace element,the granodiorite is relatively low in the total REE,and enrichmet in LREE and depieton in HREE,loss of Nb-Ta,Zr-Hf.All this show more crustal genesis,and less mantle genesis.The granodiorite positive Eu, Sr anomaly. While the biotite adamellite negative Eu,Sr anomaly, show that granodiorite source region is deeper than biotite adamellite. About tectonic setting,the formation of the rock mass is closely related with the subduction of Pacific plate,form from (syn-collision)-(aftert clllosion), producted by transformation of teconic.Now, the research on Fenshuiling complex has a great significance in summaring the laws of magmation and tectonic activity.

Abstract:It has long been regarded that the Lower Cambrian rocks were mainly from Hannan Oldland and/or Motianling Oldland in the Micangshan area, but this idea may be challenged. The Xiannüdong Formation in the Micangshan area consists of oolitic limestone, limestone breccias, and nodular limestone. According to sedimentary facies distribution, paleocurrent direction restored by cross bedding, heavy mineral assemblages and detrital zircon LA-ICP-MS U-Pb dating, we comprehensively analyzed the source areas of the Xiannüdong Formation. The temporal and spatial distribution of sedimentary facies and the direction of paleocurrents indicate that the provenance direction of the Xiannüdong Formation mainly came from the northwest and southwest, not from northwest and/or northeast judged by other predecessors. The assemblage of detrital heavy minerals, including zircon, apatite, leucoxene, chromium spinel and magnetite indicates that the sediments mainly derived from magmatic rocks, and partly from mafic magmatic rocks. LA-ICP-MS U-Pb dating for three samples of detrital zircons from the Xiannüdong Formation yielded 172 sets of effective ages. The concordia ages of detrital zircons indicate that the provenance was mainly from 744~896 Ma and 1755~2493 Ma rocks. Combined with facies distribution, paleocurrent directions, heavy mineral assemblages and detrital zircon dating, it can be concluded that the Xiannüdong Formation derived mainly from (1) the Motianling Oldland in northwest, which includes volcano-sedimentary rocks of the Bikou Group, Hengdan Group and Yudongzi Group, and Neoproterozoic intrusive rocks, and (2) the Kangdian Oldland in southwest, which consists of granite, rhyolite and diabase.

Abstract:Dry hot rock geothermal energy has received worldwide attention. Because of the huge potential of dry hot rock energy and China’s growing energy demand, in recent years, governments, universities, research institutes and enterprises have done many scientific research and technology in dry hot rock resource exploration and enhanced geothermal (EGS) development. In order to improve the exploitation of HDR resources and the construction of EGS demonstration ground in our country and ensure the current situation of geothermal resources’ exploitation in China, this paper summarized the actuality of EGS exploitation in China by collecting and organizing many relative information and research articles, and analyzed the construction and up-to-date research trends of some international and domestic typical EGS demonstration field. In this paper, experience and lessons learned during the development of the most active EGS site in the world during 2013~2016 have been summarized. Combined with the specific conditions of the existing EGS sites in China, the problems existing in the HDR prospects in China are elaborated, and suggestions for the development of dry hot rocks and the construction of demonstration sites in China are proposed.

Abstract:Dark mudstone and shales of Wufeng Formation-Longmaxi Formation in Northeast Chongqing have a thickness ranging from 30.92m to 164.47m, with the thickest layers mainly in the Xianchi section of Chaoyang Town and Tianba section of Tianba Town. Thickness also decreases toward west and the east respectively. The average total organic carbon (TOC) content in the study area is 3.32%, among which the middle area has an average TOC content of 3.93% and the west region has an average TOC content of 3.59%. Compared with 2.77% in the east, the west and east of the study area have much high TOC abundance. The dark mudstone and shales are characterized by type I organic mater, with minor type Ⅱ-Ⅱ2 kerogen distributing in the western and eastern regions. Organic matter in the study area shows generally high or even over maturity, with maturity gradually increasing from north to south. Higher contents of quartz and brittle minerals especially in the middle-western areas and lower clay mineral are better to produce gas-storage cracking and hydrofracturing. In terms of property of reservoirs, the dark mudstone and shales in the middle region are dominated by organic matter porosity with high porosity and lower permeability as well as high surface area. Gas field in the central area from Tianba, Chaoyang to Wenfeng are of better gasbearing capability. Combined the total thickness of shales, distribution of total organic carbon, and preservation conditions of reservoirs and structures, it can be concluded that the northeastern part of Chongqiang is of favorable prospecting outlook for shale gas and should be the target area for future exploration.

Abstract:In this study, nitrogen isotopic compositions (δ15N) of a series of Chinese coals were determined using Dumas combustion method to preliminarily figure out the factors affecting nitrogen isotopic compositions in coals, combined with previous results and geological background of coal deposits. The study shows that (1) The δ15N values of Chinese coals range from +1.4‰ to +5.1‰, within the range of δ15N values (+0.3‰~+5.4‰) of coals from other regions in the world. The δ15N values within the same coal profiles display heterogeneous characteristic, with the maximum of 2.5‰. (2) The δ15N values in coals are controlled by multiple effects including coal metamorphism and sedimentary environment, in which the former involves the effects of original coal grades, metamorphic grades and types, and the latter contains the effects of nitrogen sources of coal-forming plants as well as physical-chemical conditions and microbial activities of swamp medium. (3) In terms of coal metamorphism, the δ15N values of Chinese coals increase with increasing coal grade (about 1‰) but decrease at anthracite, which reflects the difference in the stability of two nitrogen isotopes. Before transforming into high rank bituminous coal, the δ15N values increase along with the preferential removal of 14N. Between high rank bituminous coal and low rank anthracite, the δ15N values decrease first and keep stable to high rank anthracite, due to the preferential removal of unstable 15 N in this stage but synchronous elimination of 14 N and 15 N after this stage. Regardless of N-containing geological fluid, hypozonal metamorphism and contact metamorphism should have the same effect on the δ15 N values in coals. (4) As for sedimentary environment, the coals from transition facies with mediumhigh and high inorganic sulfur content show higher δ15N values than the coals from lacustrine and fluvial facies with ultralow and low sulfur content, and the lowest coals δ15 N values are showed in coals from carbonate platform facies with superhigh organic sulfur content. The trend reflects the differences in nitrogen sources and degradation degrees of plant organic matter during peatification. When the microbial degradation of coal-forming precursor is weak (ultralow-sulfur and low-sulfur coals), nitrogen content in coals would be high and δ15 N would increase. When the microbial degradation of coalforming precursor becomes stronger (superhigh- organic- sulfur coals), protein would be degraded severely to lead to a decrease in nitrogen content and δ15 N again. Moreover, δ15 N in coals are also related to inertinite content, which has a relatively low δ15 N due to the loss of massive nitrogen during fusainisation. When the microbial degradation of coal- forming precursor is weak (#12 ultralow-sulfur coal bed in Sitai Mine), the control of inertinite content on δ15 N is more significant. (5) In the case of coalforming age, Late Paleozoic and Mesozoic Chinese coals show a similar average δ15 N value, which is higher than Cenozoic coals. The difference in δ15 N values is not caused by distinct plants in different coal-forming ages, but the low N loss of Cenozoic lignite without undergoing coal metamorphism.