Zircon U-Pb Dating of Leucogranite in Lhozag and Its Geological Significance

The Himalayan leucograite, which is typical production of continent-continent collision orogenic belt, has become a research hotspot of the Tibetan Plateau. The research on the leucogranite would help to verify and improve the continent-continent collision orogenic theory. （Huang et al., 2017; Fig. la）. Previous studies show the Himalayan leucogranite was mainly melted from crust materials （Guo and Wilson, 2012）. But it remains controversial for the formation model as to whether it formed from gathering of dikes or diaper of deep magma chambers.

Paleoearthquake Investigation along the Chenghai Fault Zone since~500 ka,Southeast Margin of the Tibetan Plateau

The Chenghai fault zone is located in the Sichuan–Yunnan rhombus block,which is surrounded by the Honghe River,Xianshuihe–Xiaojiang,and Jinsha River fault zones.As a mid-continental active fault,it is one of the most important seismogenic fractures in the southeast margin of the Tibetan Plateau.Geological seismic study is an important supplement to the historical seismic record;therefore,identification of paleoearthquake events in this region is of great significance to reveal the pattern and mechanism of earthquake development.In this study,detailed investigation has been carried out on the earthquake traces that formed in the Quaternary sediments in the Jinsha River section of the Chenghai fault zone,and samples for dating chronology testing were also collected.Many paleoearthquake traces were discovered in the field,including earthquake fissions,dammed lake sediments and landslides,earthquake-generated rock falls,seismic faults,and sand liquefaction veins.The collected samples were tested using optically stimulated luminescence,electron-spin resonance,and U-series methods.A total of 68 chronological samples were dated,combined with the results of field investigations,and 10 large paleoearthquake events were discovered in this region since 500 ka,which are at approximately 450,400,345,300,250,190,155,105,75,and 25 ka.Ten tectonic activity periods that produced multiple paleoearthquake events were identified since 500 ka.This study identifies paleoearthquake events in longer scales,larger spaces,and more extensive sediments,which provides new perspectives and new ideas for paleoearthquake research.

Application examples of 3D visual interpretation technology in Dagang Oilfield

3D 可视化技术是与传统的地震数据解释技术完全不同的一种新地震解释技术。这个方法作为一个单位拿地质的身体或兴趣的任何 3D 区域并且集成使 3D 成为视觉解释的身体的点，线，和飞机。这种技术能与连贯技术是综合的解释复杂差错。空间领域自动地平线跟踪能精确地决定结构的特征。目标雕刻能用倒置数据决定空间尺寸和观点 3D 岩性学身体的深度程度。我在 Qinan 的西方的斜坡在 Dagang 油矿和微妙的水库的预言的 Guanxi 区域把这种技术用于复杂的块结构的解释与好结果下垂。这研究显示视觉解释技术能广泛地并且有效地在油地开发并且到被使用改进探索成功比率。

New Zircon U-Pb Age of the Badu Dolerite:Implications for Yanshanian Magmatic Gold Mineralization within the Youjiang Basin, Southwest China

Objective The Youjiang basin,also named"Dian-Qian-Gui Golden Triangle",contains a cluster of Carlin-like gold deposits(Deng and Wang,2016).Due to the uncertainty of mineralization age and the absence of coetaneous magmatic rocks(Chen et al.,2015),the relationship between magmatism and Au mineralization still remains controversial in recent years(Hou et al.,2016).The Late

Surface pollen and modern vegetation in Southern Xinjiang,China

The study of modern pollen,and vegetation can improve the accuracy of paleoenvironmental reconstruction based on fossil pollen data.A total of 188 pollen surface samples were collected from Southern Xinjiang(34°00’–43°00’N,74°00’–94°00’E)in China,with an elevation range of 888–4530 m.Surface pollen and vegetation were studied in the northern region of the Kunlun Mountains and the southern region of the Tianshan Mountains.The results showed that the surface pollen assemblages on the southern slope of the Tianshan Mountains(3530–1124 m)were divided into three pollen zones,namely,montane steppe,montane desert steppe,and montane desert.These zones were dominated by Artemisia,Chenopodiaceae,and Ephedra pollen.The surface pollen assemblages in the eastern Pamir Plateau(4530–1287 m)could be divided into alpine meadow,montane desert steppe,and montane desert zones,which were predominantly characterized by Artemisia,Chenopodiaceae,and Asteraceae pollen.However,the Southern Tarim Basin(3548–888 m)comprised montane desert steppe and montane desert zones,which was dominated by Artemisia and Chenopodiaceae pollen.The geographic distribution of the surface pollen sites obtained using ArcGIS,the R-value,and Pearson correlation analyses indicated that the over-represented Picea and Pinus pollen were of external origin and were transported by wind,water(rivers),and ice(glacier movement).Over-representation of Ephedra and Nitraria pollen was mainly distributed in the montane desert and desert steppe zones,respectively.Pollen from Chenopodiaceae and Artemisia were over-represented and broadly distributed across Southern Xinjiang.Juglans pollen was concentrated in areas with walnut trees,strongly indicating the presence of local parent plants.According to the Hybrid Singleparticle Lagrangian Integrated Trajectory model,more Pinus pollen was transported to the Pamir region by external airflows during spring and summer,resulting in its higher surface pollen content.Research elucidating the relationship between modern pollen and vegetation in southern Xinjiang could provide data describing the surface palynological database of Xinjiang for use in large-scale paleoenvironmental reconstructions.

Earthquake-induced soft-sediment deformation structures in the Mesoproterozoic Wumishan Formation,North China,and their geologic implications

Soft-sediment structures are key to defining seismites. Two soft-sediment deformation horizons, bounded by undeformed carbonate strata, have been found in the Wumishan Formation in the Jumahe region, 175 km southwest of Beijing. One is in the lowest part of Wumishan Formation; and the other is in the uppermost part of Litho-member I. The soft-sediment structures in these two horizons fall into three categories: mould-and-sag structures, hydraulic shatterings and liquefaction dikes. The mould-and-sag structures are divided into two types: one developed in tidal-flat sediments, accompa-nied by many liquefaction-related structures and characterized by autochthonous post-earthquake sediments in sags, and the other type developed in deep-water environments, is not associated with liquefaction structures, and is overlain immediately by seismogenic tsunamites. The hydraulic shat-terings are composed of pockets of fluidization conglomerate, sand intrusions, and syndepositional faults. The liquefaction dikes fall into two categories: hydraulic-fracturing dikes and lateral-spreading dikes. The former are steep, planar, and pinch out upwards. The latter are snake-like and characterized by no diapir-related drag structures in surrounding rocks. Examination of the attitudes and strati-graphic positions of these structures suggests that these soft-sediment structures are seismogenic, and consequently, are seismites. Most seismites in the Wumishan Formation are developed near the former western, margin fault of Yanliao rift. This occurrence suggests that they could be related to movements on this fault. Other geological implications are discussed.

Growth structures and growth strata of the Qianjiadian Basin in the western Yanshan fold and thrust belt, North China

The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.

Geological Database for Plate Tectonic Reconstruction:A Conceptual Model

We all live on one planet and geology has no borders.Countries that reside on different continents share the same architecture beneath the surface;they were once neighbors with common foundations.Interoperable geological data are now freely available to everyone for the benefit of society,demonstrating that geoscience can address both global and regional problems.Whilst increasingly large datasets("Big Data")provide clear opportunities(e.g.,Spina,2018).

Wave-Enhanced Sediment-Gravity Flows in Bohai Bay Lacustrine Basin, Eastern China

Sequences of wave-enhanced sediment-gravity flows(WESGFs) have been widely recognized in the marine shelf environment. In this study, we show observations of WESGF deposits in lacustrine settings using well core and thin section data from the Paleogene in the Jiyang sub-basin, Bohai Bay basin, eastern China. The findings of this study include the following: 1) the sequence of WESGFs in the lacustrine basin is similar to that of marine; it consists of three units, MF1 unit: siltstone with basal erosion surface, MF2 unit: silt-streaked claystone, and MF3 unit: silty-mudstone; and 2) prodelta sand sheets are found in the lacustrine WESGF sequence and are classified as the MFd unit: clay-streaked siltstone. However, because the system size and variability in hydrodynamic conditions are different between the lacustrine and marine basins, lacustrine WESGFs do appear to have three distinguishable features: 1) the sediment grain size and sand content are slightly higher than those of the marine WESGFs; 2) lacustrine WESGFs may contain prodelta sediments or sedimentary sequences of other types of gravity flows, such as hyperpycnal flows; and 3) the scale of the sedimentary structures for lacustrine WESGFs is smaller. The WESGFs found in the continental lacustrine basin provide a new model for sediment dispersal processes in lake environments and may be helpful to explain and predict the distribution of sandy reservoirs for oil and gas exploration.

Rare earth element geochemical constrains on metallogeny of Jiapigou gold belt, Northeast China

Analyses of rare earth dements （REE） in gold-bearing quartz vein, granite and altered wall-rock （amphibolite） collected from Jiapigou gold belt in Southeast Jilin Province were conducted using inductively coupled plasma-mass-spectrometry （ICP-MS）. The results in- dicated that the Jiapigou gold belt underwent two periods of gold mineralization： the earlier mineralization was related to the intrusion of Neoarchaean kaligranite, where the REE of earlier gold-bearing quartz veins and Neoarchaean kaligranites were typically featured by lower concentration and positive Eu anomaly; the later mineralization was related to the intrusion of the Yanshanian granite in Mesozoic, where the REE of later gold-bearing quartz veins and Yanshanian granites were typically featured by high concentration and negative Eu anomaly. However, the metallogenic mechanisms of the earlier and of the later gold mineralization periods were analogous, metallogenic materials were heterogenous with metallogenic fluids which mainly originated from magmatic hydrothermal fluids, mixed with metamorphic fluids; the metallogenic materials were mainly derived from the altered wall rock.