Intracontinental Collisional Orogeny During Late Permian-Middle Triassic in South China: Sedimentary Records of the Shiwandashan Basin

Sedimentary response to an orogenic process is important for determining whether South China had compressional or extensional orogeny during the period from the Late Permian to the Middle Triassic besides the tectonic and magmatologic evidence. An intracontinental collision event took place between the Yangtze and Cathaysia blocks in the Late Permian. Beginning at the Late Triassic, the tectonic movement was completely changed in nature and entered a post-collisional extensional orogenic and basin-making process. This paper presents sedimentological evidence from the Late Permian to the Middle Triassic in the Shiwandashan basin at the southwestern end of the junction zone between the Yangtze and Cathaysia blocks.

Rare earth elements stratigraphic significance in late Permian coal measure from Bijie City, Guizhou Province, China

Rare earth elements （REEs） are good geological indicators. In order to understand REEs stratigraphic significance, REEs in Late Permian coal measure from Bijie City, western Guizhou Province, China were studied. The results showed that the contents of both light rare earth element （LREE） and ∑ REE were sharply increased in the boundary between Longtan Formation and Changxing Formation, which resulted from the gyration and discontinuity eruption of Emeishan basalt （REEs source） and frequent transgression-regression during forming coal. The coal measure and strata could be subdivided and correlate, and the sea-level change could be under stood by studying REEs content variation in coal measure.

Study on REEs as tracers for late permian coal measures in Bijie City,Guizhou Province,China

Analyses of Rare Earth Elements （REEs） in 13 coal samples collected from Late Permian coal measures of Bijie City in western Guizhou Province were conducted using Inductively Coupled Plasma-Mass-Spectrometry （ICP-MS）. The results indicated that REEs patterns were not controlled by materials from the sea, whereas the contribution of land plants was about 1%. The major sources of REEs were from terrigenous material as indicated by negative Eu anomaly. There were similar distribution curves of REEs between Bijie＇s coal and Emeishan basalt. M12 coal seam, which had the highest ∑REE, appeared near the boundary between Longtan Formation and Changxing Formation, which was closely correlated to the eruption of Emeishan basalt. The Emeishan basalt contributed to REEs enrichment of M12. So the sources of REEs were controlled by terrigenous material, and the Emeishan basalt was the predominant source of terrigenous material, which dominated the enrichment and pattern of REEs in Late Permian coal measure from Bijie.

Molecular Records of Primary Producers and Sedimentary Environmental Conditions of Late Permian Rocks in Northeast Sichuan,China

A series of biomarkers were identified in the aliphafic and aromatic fractions of the extracts from Late Permian Dalong （大隆） and Wujiaping （吴家坪） formations in Shangsi （上寺） Section, Northeast Sichuan （四川）, South China, on the basis of the analysis of gas chromatography-mass spectrometry （GC-MC）. The dominance of lower-molecular-weight n-alkanes throughout the profile suggests the dominant contribution of algae and bacteria to the organics preserved in the marine section. Wujiaping Formation is characterized by the elevated contribution from algae as well as other photoautotrophs such as photosynthetic bacteria as shown by the molecular ratios of hopanes to steranes or tricyclic terpanes as well as the ratio of pristane （Pr） and phytane （Ph） to C17 and C18 n-alkanes. This is in accord with the data from the microscopic measurement on the calcareous algae. In contrast, Dalong Formation is featured by enhanced contribution from bacteria and probably terrestrial organics indicated by the enhanced C24 tetracyclic terpanes relative to tricyclic terpanes. The two formations also show a distinct discrimination in sedimentary environmental conditions including redox condition and salinity. The anoxic condition was only found in the middle of the Dalong Formation as shown by the ratios of Pr/Ph and dibenzothiophene to phenanthrene, consistent with the reported data of Mo and U. An enhanced salinity indicated by the homohopane index is observed at the shallow Wujiaping Formation. On the basis of the composition of primary productivity and the redox condition, Dalong Formation is proposed, herein, to be potential hydrocarbon source rocks in the study site. It is notable that the topmost end-Permian is characterized by a large perturbauce in both the redox condition and salinity, with oxic conditions being frequently interrupted by short-term anoxia, likely showing a causal relationship with the episodic biotic crisis across the Permian-Triassic boundary.

Anomaly and geochemistry of rare earth elements and yttrium in the late Permian coal from the Moxinpo mine,Chongqing,southwestern China

The rare earth elements and yttrium(REY)of the K2 coal from the Moxinpo mine,Chongqing,were determined using inductively coupled plasma mass spectrometry(ICP-MS).The results show that REY are enriched in the K2 coal,with the average content up to 462 lg/g,much higher than average values of most coals in the world.The REY distribution patterns indicate that the light REY is enriched and show a well-pronounced Eu minimum.The fractionation of individual light-REY is higher than that of the heavy-REY.The REY distribution through the K2 coal seam shows that the top and bottom portion of the coal seam have a lower content of REY than the middle portion.Goyazite and rhabdophane were identified with a scanning electron microscope equipped with an energy-dispersed X-ray spectrometer(SEM-EDX).The REY distributions through the coal seam,SEM-EDX data and the correlation analysis between ash yields and the concentrations have revealed that the REY mainly occurs in the organic matter.The K2 coal is a potential rare-metal resource due to its high REY contents,and the coal ash could be regarded as a new and promising raw material for recovery of REY as a by-product.

Late Carboniferous-Early Permian Mafic-Ultramafic Complexes in Beishan,Southwestern Central Asian Orogenic Belt and Their Significance

Numeral Permian mafic-ultramafic complexes occur in the Beishan terrane atthe northeastern margin of the Tarim craton,southwestern Central Asian Orogenic Belt,including the Pobei,Cantoushan,Bijiashan,Hongshishan,Xuanwoling,Zhongposhan and Luodong etc.,intrusions(Qin et al.,2011;Zhang et al.,2017;Xue et al.,2018).These Beishan mafic-ultramafic complexes are composed of peridotite,pyroxenite.

Xinjiangoxylon Gen.Nov.,a New Gymnosperm from the Latest Permian of China

Following the greatest known end-Permian mass extinction plants have low diversity. Lycopsids and conifers dominated on land. A new gymnosperm Xinjiangoxylon gen. nov. is proposed based on a woody stem specimen collected from the Upper Permian （latest, Changhsingian） Upper Guodikeng Formation of the Taoshuyuan section, Turpan, Xinjiang Uygur Autonomous Region, Northwest China. The decorticated stem is characterized by a complex pith, endarch primary xylem and a thick secondary xylem cylinder. Numerous petrified woods were found in the Changhsingian at this section. However, there are rare wood fossils in the Early Triassic. The abrupt decrease of fossil woods worldwide relates to the crisis at the end of the Permian. Xinjiangoxylon turpanense gen et. sp. nov. appears to represents one gymnosperm that existed in the latest Permian.

Late Carboniferous-Early Permian Volcanic Event Deposits and Stratigraphic Correlation in Shandong Province and Its Adjacent Regions

Deposits of 10 volcanic events of 6 stages have been discovered by the authors after detailed field and lab studies of the Benxi and Taiyuan Formations in Shandong Province and its adjacent regions. They show certain temporal-spatial distribution characteristics. Volcanic fragments were probably derived from two different volcanic sources north and south of the North China Platform, while the magma of the two volcanic sources was probably derived from the lower crust. A new stratigraphic correlation scheme is put forward for the Benxi and Taiyuan Formations in this region on the basis of previous biostratigraphic work with the regionally widespread volcanic event layers as the marker bed for the isochronous stratigraphic correlation on a super-regional scale and in conjunction with the maximum transgressive event layers.

Carbon Isotope Records Indicative of Paleoceanographical Events at the Latest Permian Dalong Formation at Shangsi,Northeast Sichuan,China

Paired organic and carbonate carbon isotope compositions of Late Permian Wujiaping （吴家坪） and Dalong （大隆） formations at Shangsi （上寺）, Northeast Sichuan （四川） were analyzed by MAT 251. An abrupt negative excursion in the two isotope records was observed in the middle part of Dalong Formation, in association with a drop in the carbon isotope difference of the two records and an increase of total organic carbon （TOC） content. The negative drop of the paired carbon isotope records is suggestive of the input of 12C-enriched CO2. The molecular ratios of pristane to phytane and dibenzothiophene to phenanthrene indicate the anoxic condition in this interval. The enhanced TOC content is indicative of the elevated preservation of organic matter due to the anoxic condition. These isotopic and organic geochemical data probably infer the occurrence of the upwelling in this interval. The additional contribution of volcanism activity observed in South China cannot be excluded to the input of 12C-enriched CO2 and the negative shifts in carbon isotope composition of bulk organic matter and carbonate.

Composition and mode of occurrence of minerals in Late Permian coals from Zhenxiong County,northeastern Yunnan,China

Minerals in the Late Permian coals from the Niuchang-Yigu mining area,Zhenxiong County,northeastern Yunnan,China,were investigated using optical microscopy and low temperature ashing plus X-ray diffraction(LTA?XRD).The results showed that minerals in the coal LTAs are mainly quartz,kaolinite,chamosite,mixed-layer illite/smectite(I/S),pyrite,and calcite,with trace amounts of marcasite,dolomite,and bassanite.The authigenic quartz generally occurs in collodetrinite or as a filling in cleats or cell cavities.This silica was mainly derived from aqueous solutions produced by the weathering of basaltic rocks in the Kangdian Upland and from hydrothermal fluids.The presence of b-quartz paramorph grains in collodetrinite probably indicates that these grains were detrital and came from a volcanic ash.Clay minerals are generally embedded in collodetrinite and occur as cell-fillings.Pyrite occurs as framboidal,anhedral,and euhedral grains and a cell-filling.The coals are high in pyrite and the high pyrite content probably results from seawater invading during the stage of peat accumulation.Calcite generally occurs as vein-fillings,indicating an epigenetic origin.

Correlation and analysis of well-log sequence with Milankovitch cycles as rulers: A case study of coal-bearing strata of late Permian in western Guizhou

Based on the well-logging data of typical wells of Zhijin,Panxian and Weining areas in western Guizhou,the well-logging data GR of late Permian coal-bearing strata were processed and wavelet transform technique was used to carry out the sequence stratigraphy division and correlation.The study mainly focuses on the controlling effects which Milankovitch had on high frequency sequence,Milankovitch cycle can be used as a ruler of sequence stratigraphy division and correlation to ensure the scientifcity and the unity of sequence stratigraphy division.According to well-logging signal of the ideal Milankovitch cycle,the corresponding relation between the wavelet scales and the cycles is determined by wavelet analysis.Through analyzing analog signals of subsequence sets to search the corresponding relation between various system tracts and the features of time-frequency,the internal features of wavelet transform scalogram could be made clearly.According to ideal model research,features of Milankovitch curves and wavelet spectrum can be seen clearly and each well can be classifed into four third-order sequences and two system tracts.At the same time Milankovitch cycle can realize the division and correlation of stratigraphic sequence in a quick and convenient way.

Characteristics of Late Permian Deep Water Sedimentary Environments: A Case Study of Shaiwa Section, Ziyun County, Guizhou Province, Southwestern China

Sediments of carbonate gravity flows and terrigenous debris turbidites, and normal bathyal deposits were found at the Shaiwa Section, Ziyun County, Guizhou Province, southwestern China. Through grain size analysis of some typical sediments at this section, the changing patterns of the grain parameters and the grain size cumulations were recovered. Results show that the study area was deposited under turbidite control during the Late Permian period, which we also recognized at the outcrop section upon sedimentary characteristics of the sediments. In addition, fossils are abundant in the Upper Permian of the Shaiwa Section, including radiolarians, sponge spicules, bivalves, brachiopods, ammonoids and trace fossils. Radiolarians and siliceous sponge spicules are typical deep water assemblages. Bivalves are dominated by genera of Hunanopecten and Claraia , both showing deep water living characteristics. Ammonoids are composed of planktonic types, showing characteristics of smooth and flat shells. Brachiopods are dominated by a small and thin shelled assemblage, which are commonly flat in shape and usually of slight ornamentations on shells. In addition, trace fossils found at the Shaiwa Section are also common types of deep water facies. Thus, the fossil evidence of the Shaiwa Section also suggests a deep water environment, possibly from the bathyal slope to the basin margin facies, of the studied area during the Late Permian period.

Geochemical anomaly and the causes of transition metal accumulations in late Permian coal from the eastern Yunnan-western Guizhou region

The concentration of 39 trace elements in coal from the late Permian taken from the eastern Yunnan-western Guizhou region was determined using inductively coupled plasma mass spectrometry. It was found that the mean content of Ti, V, Cr, Mo, Co, Ni, Y, and Zr is higher than the national average. The occurrence of Mn, Ni, and Co in the different coalfields is distinctly different. Most of the enriched transition metal elements exist mainly as inorganic minerals. In the Zhina coalfield, Co, Ni, and Nb are primarily associated with sulfur. Mn, Cs, and Mo are mostly sulfides. Almost all Co was organic and a significant part of the Ni is also organic in the Liupanshui coalfield. Cs, Co, and Ni are related to sulfur in the coal taken from eastern Yunnan. Carbonate is the main form of Mn in the coal from eastern Yunnan and the Liupanshui coalfield. Ti is the oxide in the coal samples where Ti is enriched. Zr is in the form of zircon in the samples where Zr is enriched. The situation for most of the transition metal elements is consistent with terrestrial genesis. Coal seams are universally influenced by the sea. The strongly seawater effected peat bog with a reductive and alkaline environment favors the relative enrichment of Mn. A reducing environment is conducive to transition metal element enrichment.

Deep-water Ostracod Extinction in the Latest Permian:Evidence from Guangxi Province,South China

Previous studies on the Late Permian shallow-water ostracod faunas in South China have greatly increased our knowledge on the Late Permian ostracods.But the absence of data on contemporary deep-water ostracods makes it difficult to comprehensively understand the Late Permian ostracods during the largest extinction among the"Big Five"in the Phanerozoic. During the past years,our work has been focused

The Relationship between the Distribution of Thick Coal Belts and the Late Carboniferous-Early Early Permian Marine Transgression-Regression in the North China Platform

Four great second-order transgressions occurred during the Late Carboniferous to early Early Permian and they came from both the eastern and western sea areas in the North China Platform. As time went on, depocentres, depositional extent, transgression directions, coastline position and distribution of minable coal seams were changing continuously. The third great second-order transgression occurring at the beginning of the early Early Permian marks the maximum transgression period and before its arrival, i.e. at the close of the late Late Carboniferous, there was the super-regional coal-forming environment. During the second, third and fourth transgressions, the northern North China Platform was all along situated on the transgressive margin of the epicontinental sea and became the major distribution area of thick coal belts because it maintained a coal-forming environment for a long period of time from the close of the late Late Carboniferous to the Early Permian.

Analysis of Sedimentary Environment and Sequence Stratigraphy of Middle-Late Permian Sediments in Coastal Fars, Iran (Zireh Gas Field, Well ZH-A)

The current paper is focused on the facies, sedimentary environment and depositional cycles study of the Middle-Late Permian sediments in the South Fars Zireh Gas Field, the subsurface section of well ZH-A. Four hundred thin-sections obtained from cores and cuttings were examined under standard petrographic microscope. For this study research, Corel Draw X6, Corel Photo-Paint, DN2 Microscopy Image Processing System, Scope Photo, Autodesk Map, Geocalc and Auto Cad 2014 were utilized. Based on microfacies analysis and significant founa and flora, fourteen major facies in four facies associations comprising tidal flat (A), lagoon (B), shoal (C) and open marine (D) identified in the well ZH-A. This formation was deposited in inner part of a homoclinal ramp. Based on depositional cycles, seven main 3rd order sequences were revealed in the Well ZH-A. The ooid grainstone facies with interparticle and oomoldic porosity has high reservoir potential. The diagenetic processes like dolomitization and dissolution have significant effect in the reservoir quality. Based on research results, a major framework can be weaved and used to correlate reservoir layering.

Geochemical characteristics of the Permian marine mudstone and constraints on its provenance and paleoenvironment in the Fenghai area,Fujian Province, southeastern China

Permian marine strata have gradually become a research focus in the world.The marine strata of the Late Permian Dalong Formation(P3d)in the Fenghai area,Fujian Province,have become more and more important as their geochemical characteristics record important geological information and are a good indicator for recovering and reconstructing the paleosedimentary environments and tectonic attributes.The major elements,trace elements and rare earth elements were analyzed by XRF and ICP-MS,respectively.Based on the results of detailed field geological surveys,profile measurements as well as typical sample collection,the tectonic setting and provenance of Permian marine mudstone were comprehensively discussed.The results showed that the Dalong Formation(P3d)was deposited in an active continental margin tectonic environment as revealed by the relation between Fe2O3 + MgO and TiO2 and Al2O3/SiO2.The fingerprint characteristics of Mn,Fe,Co,Ni and REE and the ratio of U/Th,V/Cr,Sr/Ba,(La/Yb)N and V/(V +Ni)indicated that the sedimentary provenance was mainly derived from potassium feldspar,followed by muscovite.Sedimentary water bodies showed a gradually decreasing depositional rate trend,water depth gradually shallowing and paleo-salinity and productivity gradually increasing.Moreover,since transient delamination occurred during sedimentary processes,sedimentary water bodies showed obvious neritic characteristics.It was consistent with the results revealed by lithological and geochemical characteristics.Calcareous mudstone and siltstone transitioned into fine sandstone from bottom to top,indicating paleo-water bodies became shallow.The research results provided good reference and guidance for understanding Permian paleo-sedimentary environments and tectonic attributes of the Yong’an area,Fujian Province,southeastern China.

Characteristics of source rocks and hydrocarbon resource prospects of Permian Linxi Formation in northern Songliao Basin

In order to explore the oil and gas resource prospects in the Carboniferous–Permian strata in northern Songliao Basin,geological survey boreholes(HFD 1 and HFD 2)were drilled in the area,and thick dark mudstone and slate of the Upper Permian Linxi Formation were encountered.Source rock geochemistry analysis of the samples show that the organic matter abundance of the Upper Permian Linxi Formation source rock in the north of Songliao Basin is high,which belongs to medium to good source rock.The organic matter belongs to type Ⅱ,and it is in the evolution stage of highly mature to over mature.The Pr/Ph ratios of the source rocks range from 0.16 to 0.93,with an average of 0.53.The phytane predominance is obvious,and indicates a strong reduction to reduction sedimentary environment,which is conducive to the preservation of organic matter.Pr/nC_(17),Ph/nC_(18) and C_(27)–C_(28)–C_(29) regular steranes indicate that the organic matter was derived from a mixture of vascular plants and aquatic organisms such as algae,and is mainly contributed by phytoplankton.Through comprehensive analysis,it is considered that the source rocks of the Upper Permian Linxi Formation in northern Songliao Basin have entered the gas generation stage and have shale gas exploration prospects.

松辽盆地北部晚二叠世林西组天然气发现及意义

东北地区二叠系连续分布,发育广泛,尤其是上二叠统林西组暗色泥岩发育,沉积厚度大,分布稳定,具有良好的资源勘探前景,是上古生界有利的油气勘探层位。近年来松辽盆地石炭—二叠系油气地质调查取得了诸多进展,肇深8井营城子组所产天然气被证实来源于石炭—二叠系,四深1井见多层石炭—二叠系天然气显示(任战利等,2006),但在松辽盆地北部西斜坡区却未发现石炭—二叠系泥岩类及油气显示。

云南墨江金矿区内凝灰岩的成因及对金成矿作用的意义

云南墨江金厂金矿是哀牢山金矿带内的一个大型金矿床,矿床受剪切带控制,矿体赋存于古生代浅变质岩中,其成矿物质来源一直是争论的焦点。为进一步精确约束赋矿地层的形成时代和大地构造背景,探讨其与金成矿物质来源和成矿作用之间的关系,本文对古生代浅变质岩中的凝灰岩开展了年代学、地球化学、黄铁矿成分和同位素特征研究。LA-ICP-MS锆石U-Pb定年结果(256.6±2.3Ma)表明墨江金矿区内存在晚二叠世火山碎屑岩。锆石稀土元素含量较高,Ce正异常(δCe=2.02~32.98)和Eu负异常明显(δEu=0.06~0.38)。岩石具有低钛(TiO_(2)=0.47%~0.71%)、较高铝(Al_(2)O_(3)=10.96%~16.33%)、富铁(Fe_(2)O_(3)T=3.21%~9.12%)和硫(S=0.95%~3.92%)等特征,属于英安质-流纹质凝灰岩;此外,所有样品轻重稀土元素分馏显著((La/Yb)_(N)=7.50~15.7),Eu异常明显(δEu=0.54~0.68),亏损Nb、Ta、Ti、Sr、Ba,富集K、Pb,显示出弧火山岩的地球化学特征。Nd同位素(ε_(Nd)=-9.24~-9.61)显示富集特征,二阶段钕模式年龄为1.61~1.79Ga。凝灰岩中富含黄铁矿,黄铁矿属铁亏损型(S/Fe=2.00~2.09),存在Ni对Fe、As对S的类质同象置换;S主要来自地壳(δ^(34)SV-CDT=-8.8‰~-9.7‰);Co、Ni含量高但没有相关性,指示其为火山成因,后期受到了富Ni流体交代;黄铁矿的Au含量偏高,但未发现独立金矿物,推测可能存在纳米金。全岩地球化学特征、Nd同位素特征和锆石微量元素特征指示墨江金矿区凝灰岩形成于陆缘弧构造背景,为古特提斯洋俯冲消减过程中玄武质岩浆底侵导致古元古代变质基底重熔的产物,岩浆形成过程中伴有地幔物质的加入,同时存在金的初始富集,形成含金黄铁矿,并在随后的区域变质作用及构造热事件中发生金的活化迁移,为金矿床的最终形成提供成矿物质。晚二叠世弧岩浆作用对于墨江金矿的形成具有重要意义。