The Xuefeng Intracontinental Tectonic System (XITS) is a large-scale compressional tectonic system in the central South China block. It is characterized by northeast-trending fold-thrust belts involving the Xuefeng zone, the Chevron syncline fold-thrust zone, the Chevron anticline fold-thrust zone and the Central Sichuan basin. This paper reports detrital zircon fission track (ZFT) analyses of the sandstones sampled from Neoproterozoic to Middle Jurassic sequences, and further discusses their relation with low-temperature tectonic evolution and sediment provenance. The totally annealed ZFT data of 452-377 Ma from the Neoproterozoic and Devonian sandstones were related to an Early Paleozoic low-temperature exhumation of the Jiangnan orogen due to intracontinental orogeny in the South China block. Those annealed ZFT components from Triassic to Jurassic sandstones, grouped 236-189 Ma, 189-142 Ma, and 142-124 Ma decreasingly from east to west structurally imply a northwestward progressively squeezing by the Xuefeng intracontinental orogeny as a result of the Paleo-Pacific subduction. The unannealed age components (411 Ma, 362-377 Ma, 270-216 Ma, and 209-183 Ma) of the Upper Triassic to Middle Jurassic sandstones, are comparable to the multistage tectonic evolution of the Qinling orogen through subduction, accretion and collision and are therefore indicative of sample potential provenance.

Drilling has revealed suites of magnesian granite and diorite emplaced in Early Jurassic time (198-195Ma) and an arc-related low-temperature (678 to 696 degrees C) magmatism in NE South China Sea. These rocks have Sr-87/Sr-86(i) (0.705494 to 0.706623) and epsilon Nd-t (-0.9 to +2.2) as evidence of evolved mantle-derived magmas, coupled with enriched fluid-mobile elements Cs to K and Pb implying involvement of subduction-zone fluids. Another Early Jurassic granodiorite (zircon U-Pb 187Ma) drilled from the SW East China Sea, a magnesian high-K calc alkaline, is comparably confined to a range of low-temperature (675 degrees C) arc-related granite, characterized by enrichment of fluid-mobile elements and Nb-Ta depletion. Its Sr-Nd isotopes (Sr-87/Sr-86(i)=0.705200, epsilon Nd-t=1.1) suggest a product of evolved mantle-derived melts. Together with detrital igneous zircons from Paleocene sequences, these observations reveal an Early Jurassic arc-related low-temperature (600 to 740 degrees C) magmatism in the SW East China Sea. These arc-related granitoids, along with those from SE Taiwan, could define an Early Jurassic NE-SW trending Dongsha-Talun-Yandang magmatic arc zone along the East Asian continental margin paired with Jurassic accretionary complexes from SW Japan, East Taiwan to the West Philippines. This arc-subduction complex assembly was associated with oblique subduction of the paleo-Pacific slab beneath Eurasia, presumably responsible for Early Jurassic lithospheric extension in south China block.

苏北盆地东台坳陷砂岩统计结果表明,碎屑岩岩屑以火成岩和变质岩岩屑为主,早期(泰州组)以火成岩岩屑为主,晚期(古新统)以变质岩岩屑为主.Dickinson三角投图表明,物源区的大地构造背景属于再旋回造山带.东台坳陷重矿物纵向上变化特征指示古近纪三垛组沉积时期,物源区隆升强烈,剥蚀加速,导致不稳定重矿物显著增加.物源区对比结果揭示出张八岭隆起带是东台坳陷碎屑岩的主要物源区,其抬升过程对苏北盆地古近系的沉降活动具有强烈的控制作用.

The granitoid suites encountered by drilling in the northern South China Sea (SCS) remain important for understanding the evolution of the late Mesozoic Southeast Asian continental margin. They comprise a range of rock types including diorite, tonalite, granodiorite, monzogranite and syenogranite with SiO2 spanning 56.4–76.8%. Newly acquired secondary ion mass spectrometry (SIMS) U–Pb ages of samples from 14 boreholes indicate two key magmatic episodes: Late Jurassic (161.6–148.2 Ma) and Early Cretaceous (136.5–101.7 Ma). Jurassic magmatism probably began in late Middle Jurassic time, documented by the dates of inherited zircons. The granitoids are dominated by metaluminous to weakly peraluminous I-type granites, are transitional between magnesian and ferroan, and encompass calc-alkaline, high-K calc-alkaline, and shoshonitic series. The geochemical signatures suggest that these granitoids were mostly generated in a normal continental arc environment. Notable features of the I-type samples are well-defined negative Nb–Ta–Ti anomalies typical of arc-related magmas. Taken together, the late Mesozoic arc granites of the SCS, the accretionary wedge of the Palawan terrane to the southeast, and the zone of lithospheric extension north of the SCS throughout Southeast China, define a southeast-to-northwest trench-arc-backarc architecture for the late Mesozoic Southeast Asian continental margin whose geodynamic setting is related to subduction of the Palaeo-Pacific slab beneath the Asian continent. Two key subduction episodes are recognized, one in Late Jurassic and the other in Early Cretaceous time.

South Yellow Sea Basin is one of the major petroliferous basins offshore China .It has been explored for years but with no significant commercial discovery due to a lack of understanding of its structure ,diversified fault systems and complicated tectonic evolution .To evaluate the exploration potential and gain insight into faulting activities and sedimen-tation of the basin , we performed characterization of the tectonic deformation and formation mechanism analyses of the northern sub-basin in South Yellow Sea Basin since the Late Cretaceous based on a combination of the latest two-dimension seismic data with relevant geologic setting , drilling data and previous research papers .It shows that thrust faults were formed in the marine strata due to the compression and deformation the Indo-China period,and the fault sys-tem served as the basement faulting system since the Late Jurassic .It was later reactivated by extension and controlled the activities of faults within the basin as well as the sedimentary framework .A faulted depression cluster that was domi-nated by extensional structural deformation formed ,reflecting a relationship of shallower strata being constrained by the deeper ones.

Whether there are terrestrial responses to the Oceanic Anoxic Events (OAEs) remain enigmatic. In this paper, we report a case study in the Lower Cretaceous continental and transitional sequences of coastal southeastern China. It may represent the first late Aptian to Albian terrestrial carbon isotope record from China. Several organic-rich black shale and grayish black mudstone horizons were found to develop widely in the coastal southeastern China during the period from 113 ± 3 Ma to 99 ± 3 Ma, when the Cretaceous OAEs were recorded primarily in marine sequences. Organic carbon isotope (δ13Corg), total organic carbon (TOC), and total nitrogen (TN) were analyzed for the black shales from two sections, i.e., the Shipu transitional and Chong'an continental sections. Five negative δ13Corg excursions can be recognized for both the sections, termed as SI–SV and CI–CV events for the Shipu (S) and Chong'an (C) sections, respectively. Correlations between δ13Corg, TOC and N/C ratio suggest that the SI–SIII and CI–CIII events might have been caused by global factors, i.e., the OAE1b event based on analogs to typical OAE1b reported in the Tethyan and Pacific basins. They archived the terrestrial carbon isotope response to the OAE1b accompanied with a disturbance of carbon isotope in carbon reservoir of the global ocean–atmosphere system under a warm and humid climate.

Compared to the northern South China Sea continental margin, the deep structures and tectonic evolution of the Palawan and Sulu Sea and ambient regions are not well understood so far. However, this part of the southern continental margin and adjacent areas embed critical information on the opening of the South China Sea (SCS). In this paper, we carry out geophysical investigations using regional magnetic, gravity and reflection seismic data. Analytical signal amplitudes (ASA) of magnetic anomalies are calculated to depict the boundaries of different tectonic units. Curie-point depths are estimated from magnetic anomalies using a windowed wavenumber-domain algorithm. Application of the Parker–Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. The Palawan Continental Block (PCB) is defined by quiet magnetic anomalies, low ASA, moderate depths to the top and bottom of the magnetic layer, and its northern boundary is further constrained by reflection seismic data and Moho interpretation. The PCB is found to be a favorable area for hydrocarbon exploration. However, the continent–ocean transition zone between the PCB and the SCS is characterized by hyper-extended continental crust intruded with magmatic bodies. The NW Sulu Sea is interpreted as a relict oceanic slice and the geometry and position of extinct trench of the Proto South China Sea (PSCS) is further constrained. With additional age constraints from inverted Moho and Curie-point depths, we confirm that the spreading of the SE Sulu Sea started in the Early Oligocene/Late Eocene due to the subduction of the PSCS, and terminated in the Middle Miocene by the obduction of the NW Sulu Sea onto the PCB.

In the northern Tian Shan foreland basin, northwestern China, the thick Cenozoic terrigenous succession is crucial for paleoclimate–environmental reconstruction of the Asian interior. Here we present a detailed rock magnetic investigation on 245 samples from the ~1200-m-thick Neogene Taxi He section with a magnetostratigraphic age span of ca. 8.0 to 2.0Ma in the northern Tian Shan foreland basin. Our rock magnetic results indicate that the significant variations in composition, concentration and grain size of magnetic minerals occurred at ca. 6.0, 3.7 and 2.7Ma. The comparable compositions of rare earth elements (REEs) throughout the Neogene Taxi He section suggest no significant modification of the source materials during the interval between ca. 8.0 and 2.0Ma, and thus sediment provenance is not regarded as responsible for these observed variations in rock magnetic properties. Our further analyses show that the variations in magnetic properties of the Taxi He section are casually linked mainly with lithofacies transition due to range encroachment into foreland basin as well as climate aridification. Identified enhancement of aridification was chronologically constrained at ca. 6.0 and 2.7Ma. Such climate events are important archives for reconstructing the Late Cenozoic paleoclimatic history of the Asian interior. Further comparison between different paleoclimate records clearly indicates that magnetic parameters such as S−100mT are potentially effective proxy indices for paleoclimate–environmental reconstruction in the Tian Shan foreland basins and the nearby areas.

Eclogites from the Huwan shear zone in the western Dabie were investigated in terms of their P-T evolution, geochemistry, and combined Lu-Hf and Sm-Nd geochronology. Trace element and isotope data suggest a normal mid-ocean ridge rather than an intraplate or ocean island setting for the protoliths of the eclogites. Electron microprobe analyses of representative garnets show typical prograde zoning profiles. Estimated peak metamorphic temperatures of 540-590 degrees C most likely did not exceed the closure temperature of the Lu-Hf and Sm-Nd systems. The consistent Lu-Hf and Sm-Nd ages, therefore, most likely reflect garnet growth and are interpreted to reflect high-pressure eclogite-facies metamorphism due to the occurrence of omphacite inclusions from core to rim in garnets and the spherical geometry effect despite the well-preserved prograde zoning in the garnets. The high-pressure mineral assemblage of the eclogite yielded a statistically robust Lu-Hf age of 260.0 +/- 1.0 Ma (2 sigma, 10 points, MSWD = 1.0) and a Sm-Nd age of 260.4 +/- 2.0 Ma (2 sigma, 9 points, MSWD = 1.4), which are younger than the Carboniferous zircon U-Pb ages of ca. 310 Ma. The new Lu-Hf and Sm-Nd data, in combination with published geochronological data, define two distinct Carboniferous and Permian population ages for the oceanic-type eclogites from the Huwan shear zone, which may require that these rocks experienced two episodes of high-pressure metamorphism within less than 50 Myr. (C) 2012 Elsevier Ltd. All rights reserved.

Combined apatite fission track (AFT) and (U-Th)/He (AHe) thermochronometries can be of great value for investigating the history of exhumation of orogenic belts. We evaluate the results of such a combined approach through the study on rock samples collected from the Baluntai section in the Tianshan Mountains, northwestern China. Our results show that AFT ages range from ∼60 to 40 Ma and AHe ages span ∼40–10 Ma. Based on the strict thermochronological constraints imposed by AHe ages, forward modeling of data derived from AFT analyses provides a well-constrained Cenozoic thermal history. The modeled results reveal a history of relatively slow exhumation during the early Cenozoic times followed by a significantly accelerated exhumation process since the early Miocene with the rate increasing from <30 m/Myr to >100 m/Myr, which is consistent with the inference from the exhumation rates calculated based on both AFT and AHe age data by age-closure temperature and mineral pair methods. Further accelerated exhumation since the late Miocene is recorded by an AHe age (∼11 Ma) from the bottom of the Baluntai section. Together with the previous low-temperature thermochronological data from the other parts of the Tianshan Mountains, the rapid exhumation since the early Miocene is regarded as an important exhumation process likely prevailing within the whole range.

Five Paleogene volcanics sampled from the northern South China Sea were analyzed via LA-ICP-MS zircon U-Pb dating,including basalt and andesite from Borehole SCSV1 and volcanic agglomerate from Borehole SCSV2,respectively.A total of 162 zircon U-Pb dates for them cover an age range from Neoarchean to Eocene,in which the pre-Paleocene data dominate.The Paleogene dates of 62.5±2.2 Ma and 42.1±2.9 Ma are associated with two igneous episodes prior to opening of South China Sea basin.Those pre-Paleocene zircons are inherited zircons mostly with magmatogenic oscillatory zones,and have REE features of crustal zircon.Zircon U-Pb dates of 2518–2481 Ma,1933– 1724 Ma,and 1094–1040 Ma from the SCSV1 volcanics,and 2810–2718 Ma,2458–2421 Ma,and 1850 –993.4 Ma from the SCSV2 volcanics reveal part of Precambrian evolution of the northern South China Sea,well comparable with age records dated from the Cathaysia block.The data of 927.0±6.9 Ma and 781±38 Ma dated from the SCSV2 coincide with amalgamation between Yangtze and Cathaysia blocks and breakup of the Rodinia,respectively.The age records of Caledonian orogeny from the Cathaysia block are widely found from our volcanic samples with concordant mean ages of 432.0±5.8 Ma from the SCSV1 and of 437±15 Ma from the SCSV2.The part of the northern South China Sea resembling the Cathaysia underwent Indosinian and Yanshannian tectonothermal events.Their age signatures from the SCSV1 cover 266.5±3.5 Ma,241.1±6.0 Ma,184.0±4.2 Ma,160.9±4.2 Ma and 102.8±2.6 Ma,and from the SCSV2 are 244±15 Ma,158.1±3.5 Ma,141±13 Ma and 96.3±2.1 Ma.Our pre-Paleogene U-Pb age spectra of zircons from the borehole volcanics indicate that the northern South China Sea underwent an evolution from formation of Precambrian basement,Caledonian orogeny,and Indosinian orogeny to Yanshannian magmatism.This process can be well comparable with the tectonic evolution of South China,largely supporting the areas of the northern South China Sea as part of southward extension of the Cathaysia.

天山造山带新生代剥露过程一直受到普遍关注.对沿横穿天山的乌鲁木齐-库尔勒公路胜利达坂以南段采集的基岩样品进行了详细的磷灰石裂变径迹分析.热史模拟结果显示,该段天山的新生代剥露历史分为两个阶段,即古近纪期间的缓慢剥露阶段和中新世以来的快速剥露阶段,其剥露速率分别为＜30m/Ma和70～ 160m/Ma.综合分析前人在东天山、北天山以及南天山等天山不同区域取得的低温热年代学数据,我们认为,新生代天山造山带可能经历了4次快速剥露过程,分别开始于新生代早期(67 ～ 65Ma)、始新世中期(约40±5Ma)、渐新世末-中新世中期(约20±5Ma)以及中新世中晚期(约10±2Ma).这4次快速剥露过程分别发生于造山带的某一或某些区域,表明新生代天山地区的剥露过程存在明显的空间差异性.从整个天山造山带来看,渐新世末-中新世中期开始的快速剥露影响范围可能最广,是新生代天山地区一次重要的剥露作用过程.

Tectonically, the northwestern South China Sea (SCS) is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene (5.3 Ma), the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha Trough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimentary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in the Yinggehai-Qiongdongnan-Xisha trough area, which is characterized by thinner crust (<16 000 m), half-graben or graben structural style and thicker sedimentary sequences (>3 500 m). A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement velocity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate.

A study of LA-ICP-MS zircon U-Pb dating and geochemical analysis is performed on Neoproterozoic igneous rocks from the southern part of Sulu orogenic belt to obtain their crystallization time and tectonic control.Zircon U-Pb dating results yield weighted mean crystallization ages of(806.0±14.0)Ma for the gneissic granite from Jinping Mountain,(800.8±7.8)Ma for metavolcanic rocks of the Yuntai Formation,Haizhou Group in the Lianyungang area,together with(751.6±7.1)Ma and(767.0±15.0)Ma for metavolcanic rocks of the Xileng Formation,Zhangbaling Group from the Zhangbaling belt.These igneous rocks are characterized with high K calc-alkaline series,medium negative Eu anomaly and medium depletion of the HREE.They are predominately depleted in Nb,Ta,Sr,P and Ti,and the concentrations of high Yb and low Sr show the same characteristics as those for Zhejiang-Fujian type granite.These are correlated with the tectonic setting of extension and partial melting from the lower crust,corresponding to the Rodinia break-up and lithospheric thinning.

In an effort to further advance our understanding of the evolution of the Sulu–Dabie orogen and its complex interactions with the Tanlu fault, and to tackle non-unique geophysical interpretations, we characterize the 3D geological structures and dynamics of the Sulu–Dabie orogen and its environs using various data processing and interpretation of a very large suite of gravimetric, magnetic, magnetotelluric, geothermal, and seismic data. We have modeled regional geothermal field of the lithosphere by incorporating both surface heat flow and Curie-point depths inverted from magnetic anomalies. This gives better constraints on regional thermal lithospheric thicknesses, which are found to be small (mostly between 55 and 95km), conformable to other geophysical results, and supportive of lithospheric de-rooting. From regional geotherms and Bouguer gravity anomalies, we assess depths, temperatures and heat flow of the Moho, and find that mantle contributes a little over 70% of the total surface heat flow. Large differences in thermal lithospheric thicknesses and geothermal activities are found between the Sulu and the Dabie segments of the Sulu–Dabie orogen. These differences result, at least partially, from large vertical differential movement at the lithospheric scale across the Tanlu fault, as seen from both reflection seismic sections and gravity anomalies. Within the Sulu–Dabie orogenic belt, reduction to the pole and 3D analytic signal analysis on magnetic anomalies reveal that positive magnetic anomalies associated with this belt are most due to gneiss, migmatite and Mesozoic granites, whereas ultrahigh-pressure metamorphic zones show weak or negative magnetic anomalies. This interesting magnetic contrast between ultrahigh-pressure metamorphic rocks and surrounding rocks suggests that ultrahigh-pressure metamorphic minerals are either only weakly magnetized, or possibly retrograded and remagnetized over a long time span or in a period of reversed magnetization. High-pressure metamorphic minerals of blueschist facies appear to be less susceptive than ultrahigh-pressure metamorphic minerals.

The paleoelevation reconstruction of an orogen is of great significance to the study of mountain building and of paleoclimate.The authors use the thermal history data of low-temperature thermochronology to reconstruct the paleoelevation of the Dabie orogen since Late Cretaceous.The reconstruction procedure includes(in order) the following: digitalizing the low-temperature thermal history modelling curve of the Dabie orogen,extracting the time-temperature data,calculating the average exhumation thickness of the focused region by the spatial interpolation method,the deflection isostatic correction,the calculation of the average paleoelevation change,and the two-dimensional integral calculation to get the amplitude decrease of paleotogography.The result shows that the average exhumation thickness of the Dabie orogen since 90 Ma is about 5.44 km,and the average elevation decrease of paleotogography is 2.86-4.16 km,the upper limit of the amplitude decrease of paleotogography is 4.49-6.53 km.

造山带古高度的恢复对研究造山过程与古气候有重要意义。利用低温年代学热史数据恢复大别造山带晚白垩世以来的古高度。恢复流程包括将大别造山带低温热史模拟曲线数字化,提取时间温度数据,通过空间插值方法计算研究区域平均剥露厚度,再通过挠曲均衡校正,计算平均古高度变化量,最后通过2维积分计算古地形波幅降低量。结果显示:90 Ma至今,大别造山带平均剥露厚度达约5.44 km,而古地形平均高度降低2.86～4.16 km,古地形波幅降低的上限为4.49～6.53 km。

Early cretaceous-paleocene geothermal gradients of Sichuan Basin are reconstructed from 27 vitrinite reflectance profiles.Results show that ancient geothermal gradients are between 20~25℃·km-1 and are higher in the eastern and southern regions of the basin than in the western and northern regions.According to comparison of ancient and Current geothermal gradients,geothermal gradients descended in eastern and northeastern but increased in the central and southern regions since the late Mesozoic,while kept unchanged in western Sichuan Basin since the early Cenozoic.According to the tectonic evolution in this area,thermal history of Sichuan Basin in the Mesozoic and Cenozoic was mainly affected by the late Permian tectono-thermal event,the evolution of the lithospheric thickness since the late Mesozoic and the recent active tectonics.The late Permian tectono-thermal event affected most parts of Sichuan Basin.Current active tectonics have significant impact on southern Sichuan,and the evolution of the lithosphere thickness may be the main factors influencing the Mesozoic-Cenozoic thermal history of Sichuan Basin.

It is difficult to acquire a corresponding relationship between temperature and time using reflectance of vitrinite as a major geothermometer. In order to reveal characteristics of the tectono-thermal evolution of the outcrops of south Lower Yangtze area and its regional controls, detailed zircon fission track analysis (ZFT), which can depict a good corresponding relationship between temperature and time, on fifteen Palaeo-Mesozoic clastic rocks was carried out. The results show that the Palaeo-Mesozoic clastic rocks have zircon fission-track ages ranging from 214 to 75 Ma. These ZFT ages (pooled ages or central ages) coupled with ZFT grain ages show characteristics of regional thermal variation, corresponding to the difference of tectonothermal reconstruction and differential ZFT annealing properties. The ZFT ages dominantly concentrate on the period of 157 to 95 Ma, as a magnificent feature, according with the time of 160-100 Ma for large-scaled magmatism that ocurred in the Lower Yangtze and Southeast China. It follows that this magmatism is considered to exert appreciable influence upon sample ZFT thermochronology. Two younger ZFT results (ZFT10 and ZFT11) of 75 and 76 Ma from the Nanhua Series are associated with faulting of the NW-SE structural zone.

The in-situ remelting theory of granite opens a new perspective for the study of the tectonic cause of the spatial and temporal distribution of the Late Mesozoic(Late Jurassic-Early Cretaceous) granite in South China.By comparison,we found that there is a high degree of similarity and consistency in the spatial and temporal distribution of granite and the stress field in the Late Mesozoic between the Dabie-Sulu orogenic belt and its north vicinity(especially the Sulu orogenic belt and its north vicinity) and South China.That is,the granite distribution is mainly along the NE direction,turns from old to new from NW to SE,and is under the control of the same stress field caused by the high-speed subduction of the paleo-Pacific plate towards the Eurasia continent.On the basis of this theory,we may conclude that the Late Mesozoic(Late Jurassic-Early Cretaceous) granite of the Dabie-Sulu orogenic belt and its north vicinity and the Late Mesozoic(Late Jurassic-Early Cretaceous) granite of South China were very likely formed by the same event,that is,the subduction of the paleo-Pacific plate towards the Eurasia continent.The linkage effects between the plates caused by the subduction of the paleo-Pacific plate led to the friction between the South China plate and the North China plate,and as a result,the temperature of the crust increased and the granite magma layer formed.With the change of subduction speed,the position of the granite remelting interface moved and thus brought about the tendency that the Late Mesozoic granite became newer from NW to SE(at least the Sulu orogenic belt seems to be like this).