Tectonic Environments of Cenozoic Volcanic Rocks in China and Characteristics of the Source Regions in the Mantle

Extensive volcanism is one of the important features of Cenozoic geology in China.Based on temporal-spatial distribution,the volcanism was associated with three major different geological settings:1)the continental rift basalts in Northeast and North China;2)the tension-fault basalts on the continental margins of Southeast China; and 3) the collision-zone high-K volcanics in the Qinghai-Xizang Plateau and its vicinities.The characteristics of “depletion in the south and enrichment in the north“of the China continental mantle are strongly supported by isotopic evidence.The Cenozoic continental cal characters,into the following geochemical provinces:1)the depleted mantle in South China;2)the primary mantle in Northeast and NorthChina; 3)the hybrid and transi-tional mantle in the region of Shandong ,Anhui,Jiangsu and northern Zhejiang;4)the depleted mantle around the Bohai Bay and the Lower Liaohe River;5)the K-metasomatic enriched mantle in the northern part of Northeast China;and 6)the re-cycled enriched mantle in the ancient subduction zone in the Qinghai-Xizang Plateau and its surround-ings.These geochemical characteristics on a regional scale must be a reflection of the nature of lithosphere evolution.     

Sedimentary Characteristics of the Cretaceous in the Songliao Basin

The rupture of the lithosphere in Late Jurassic brought about the eruption of basaltic magma in the Songliao Basin. The evolution of the basin in Cretaceous progressed through six stages: pre-rift doming, extensional fracturing, fault subsidence, fault downwarping, downwarping and shringkage, resulting in the deposition of terrstrial facies nearly 10,000 m thick. There are different depositional sequences in these stages: the depositional period of the Early Cretaceous Shahezi and Yincheng Formations is the development stage of the down-faulted basin, forming a volcanic rock-alluvial fan-fan delta-lacustrine (intercalated with episodic turbidites)-swamp facies sequences; the period of the Early Cretaceous Dengluku Formation is the transformation stage of fault subsidence into fault downwarping of the basin, forming a sequence mainly of alluvial plain-lacustrine facies; the depositional period of the Early Cretaceous Quantou Formation-Late Cretaceous Nenjiang Formation is the downwarping stage of the basin, forming an alluvial plain-delta-lacustrine facies sequence; the period of the Late Cretaceous Sifangtai Formation-Mingshui Formation is the shringkage stage of the basin, forming again a sequence mainly of alluvial plain-alluvial fan and small relict lacustrine facies. These vertical depositional sequences fully display the sedimentary characteristics of a failed continental rift basin. Many facts indicate that the two large-scale lake invasions, synchronous with the global rise of sea level, which took place in the downwarping stage of the basin development, led to the connection between the lake and sea.     

The Origin of the Mesozoic Associated Multiseries Granitoid Magma in the Shandong Peninsula

Three melting events of the earth's crust occurred during the period of 220-120 Ma in the Shandong Pe-ninsula. Three subcycles of granitoid magma including six rock series were generated in the faulted granitoidmagma belt. The parent magma of several rock series formed earliest originated from the lower crust ofgranulite facies; following the increase of geothermal temperature the source magma would migrate into themiddle crust of amphibolite facies. In the diapiric granitoid magma belt, the granitoid magma was formed firstin granitic layer of the upper crust, and then in the middle crust. In each subcycle the generation of magmastarted with the generation of more mafic one and finished with low eutectic one; they were formed in the formof layered melting in a particular position of the crust.     

Sinian-Cambrian Tectonic Framework in the Tarim Basin and its Influences on the Paleogeography of the Early CambrianEI北大核心CSCD

Due to strong remodification and sparse trace remnants, tectonic restoration is critical for the reconstructing of the paleography and basin-prototype in the multiple-cycles superimposed basin, which is also fundamental for the hydrocarbon exploration of the deep marine carbonate in the Tarim Basin. This study presents the tectonic framework of the transition phase from the Sinian to the Cambrian Period and its constrains on the paleography of the Cambrian in the Tarim Basin based on comprehensive analysis of new geochronology data, seismic data and regional tectonic data. The results showed that (1) there is a large regional unconformity between the Cambrian and Precambrian, suggesting a discontinuous deposition from the Sinian to the Cambrian that is contrary to the major view; (2) a broad flattened paleotopography formed before Cambrian Period, which is favorable for the wide epicontinental sea environment and a gentle homoclinal ramp platform development in the early Cambrian, and the residual basement low relief uplifts that influence the microfacies differentiation in the carbonate platform; (3) the Cambrian carbonate platform has been involved much into the marginal orogenic belts, and the proto-platform is probably of 200 km out of the present basin in S-N direction; (4) there is a weak extensional setting in the Cambrian-Early Ordovician rather than a strong rifting setting with a large aulacogen into the platform, in which a inter-platform shallow depression and stable ramp platform developed in the Cambrian; (5) there is not troughs, but rather low relief uplifts developed in the Early Cambrian in the southwestern Tarim Basin, and lack of large uplifts along the carbonate platform margins; (6) it is showed a broad architecture of platform-wide slope-ocean basin from the inner Tarim plate to its margin in the Cambrian Period. Considering the basin prototype, the restoration of the tectono-paleography in the early Cambrian in the Tarim Basin is distinct from those of the previously proposed. We propose that a gentle pattern with “two platforms and one inter-depression” in E-W striking other than multiple small platform constrained in the basin, and further subdivision of the western platform with inner platform low uplift and sag in N-S striking, which is possibly inherited from the basement architecture. On the outer of the united platform, there is probably broad gentle slope for transition to ocean basin. We therefore argue that tectonic restoration is crucial for reconstruction of the paleogeography and basin prototype, especially for basins experienced multiphase of tectonic cycles. © 2018, Science Press. All right reserved.     

Newly developed evidence for the original Tethysan island-arc volcanic rocks in the southern segment of the South Lancangjiang Belt

This paper re-describes the characteristics of pre-Ordovician (Pt3) metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province from the aspects of petrographic characteristics, rock assemblage, petrochemistry, REE, trace elements, lead isotopes and geotectonic setting. The metamorphic volcanic rocks maintain blasto-intergranular and blasto-andesitic textures; the volcanic rocks are characterized by a basalt-andesite-dacite assemblage; the volcanic rocks are basic-intermediate-intermediate-acid in chemical composition, belonging to semi-alkaline rocks, with calc-alkaline series and tholeiite series coexisting, and they are characterized by low TiO2 contents; their REE distribution patterns are of the LREE-enrichment right-inclined type; the volcanic rocks are enriched in large cation elements and commonly enriched in Th and partly depleted in Ti, Cr and P, belonging to the Gondwana type as viewed from their Pb isotopic composition; petrochemically the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the region studied.     

Prognosis of the state （eutrophication and pollution） of freshwater ecosystems on the example of long-term research into Lake Baikal

Systematic （monthly） observations of changes in the components of trophic status in the pelagic zone of Baikal were carried out during years of spring blooms of almost pure cultures： Gymnodinium （1965）, Aulocoseira bai-calensis （1968）, Synedra acus （1969）, Nitzschia acicularis （1984 and 1987）, picocyanobacteria （2004-2005）. The research period coincided with various anthropogenic impacts on Baikal ecosystem： （1） the period of the natural state of the lake （until 1969）; （2） the period of weak anthropogenic impact （until 1985）; and （3） the period of acute anthropogenic impact. In the third period the following was found in the deep-water part of the lake： the episodic appearance of ammonium and nitrite nitrogen; change in the components of suspended matter （SM）; disturbed patterns of seasonal changes in SM content, chlorophyll-a, organic forms of carbon, nitrogen and phosphorus; the average annual concentrations of suspended organic carbon, nitrogen and phosphorus have increased considerably; the vertical distribution pattern of minerals and organic forms of nitrogen and phosphorus have been disturbed; finally, an observed inverse correlation between winter nitrogen content and the spring concentration of chlorophyll-a （1986-1989） would indicate the presence of toxins in the lake. This led to the study of POPs in Baikal and the Baikal region. Investigations undertaken during 2004-2005 in the pelagic coastal zones of the lake indicated the presence of toxic pollutants in southern Baikal （the correlation between winter nitrogen content and spring concentration of chlorophyll-a is inverse and equals 0.99 and 1.00 respectively）. Toxicants that enter the lake during the iced-over period mainly enter the trophogenic layer, as wastewaters are warmer than the lake waters, depress the development of endemic spring diatomic algae and lead to a rise in the trophic status.     

Influence of the Chuxiong Yao’an Earthquake on the Mineralization of Hot Springs in the Tengchong Geothermal Area, Southwestern China

<正>The Tengchong geothermal area,an active tectonic region with frequent earthquakes,is located in Yunnan Province of southwestern China.This area contains abundant active hot springs, which often display high metal concentrations and obvious mineralization phenomena.At 19:19 on 9 July 2009,an earthquake occurred in Yao'an,Chuxiong,Yunnan Province,which is 300 km to the northeast of the Tengchong geothermal area.We sampled water in the hot springs in the Tengchong area from 4 July to 9 July 2009 and from 10 July to 15 July 2009 to study the changes of elemental concentrations before and after the earthquake and discuss the influence of the earthquake on the mineralization of the hot springs.The concentrations of most trace elements increased slightly,but the concentration of REE(rare earth elements) decreased by 50%after the earthquake in the hot springs around a NS-trending fault.The elemental concentrations remained unchanged in Longtan and Suanshuigou,which are related to an inactive crater.The elemental concentrations in other springs controlled by superficial and small-scale faults decreased after the earthquake.The earthquake can stimulate the activity of deep faults and magma chambers,as is responsible for the increase of metal concentrations in the hot springs along the NS-trending deep fault;whereas it can decrease the porosity of permeable rocks,resulting in the decline of the flux of ore-bearing fluids and the corresponding mineralization in the hot springs related to superficial faults.     

Sporopollen Assemblages from the Cretaceous Yimin Formation of the Hailar Basin, Inner Mongolia, China

Three sporopollen assemblages are recognized for the first time from the Cretaceous Yimin Formation in the Hailar Basin of eastern Inner Mongolia. They are （in ascending order）： the lmpardecispora-Aequitriradites- Clawttipollenites assemblage; the Triporoletes-Pilosisporites-Asteropollis assemblage; and the Appendicisporites- Asteropollis-Tricolpites assemblage, distributed in Members 1, 2 and 3 of the Yimin Formation respectively. Recognition of this biostratigraphic sequence is very important for the division and correlation of the Yimin Formation in the basin. Meanwhile, the age of the Yimin Formation is considered to be Barremian to Early Albian based on the palynological data.     

Geothermal Model of the Fore-Yenisey Sedimentary Basin―Transitional Structure between the Ancient Siberian Platform and the Young West Siberian Plate

Results of the investigation into the geothermal regime of the Fore-Yenisey sedimentary basin, formed during the collision and subsidence of the Kas-Turukhan microcontinent and the western margin of the Siberian craton in the late Neoproterozoic and early Paleozoic are reported. It was established that the structural and geothermal conditions of the upper Precambrian–Paleozoic sections are similar to those in the western regions of the Siberian platform and are characterized by rather low geothermal gradients (12.5–25.5 °С/km). In the western parts of the basin, formation temperatures in the uppermost pre-Jurassic sediments are 50°С–85°С, decreasing eastward to 30°С–55°С. For the first time, the detailed geothermal model of the basin sedimentary fill was developed. This model allows predictions of the geothermal conditions of Earth’s interior.     

Sedimentary Evolution of the Qinghai–Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau

We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene–Eocene, Oligocene, Miocene, and Pliocene of the Qinghai–Tibet Plateau by compiling data regarding the type, tectonic setting, and lithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. (1) The Paleocene to Eocene is characterized by uplift and erosion in the Songpan–Garzê and Gangdisê belts, depression (lakes and pluvial plains) in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai–Tibet Plateau. (2) The Oligocene is characterized by uplift in the Gangdisê–Himalaya and Karakorum regions (marked by the absence of sedimentation), fluvial transport (originating eastward and flowing westward) in the Brahmaputra region (marked by the deposition of Dazhuka conglomerate), uplift and erosion in western Kunlun and Songpan–Garzê, and depression (lakes) in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. (3) For the Miocene, a widespread regional unconformity (ca. 23 Ma) in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions (lakes) in the Tarim, Qaidam, Xining–Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18–13 Ma, and north–south fault basins formed in southern Tibet ca. 13–10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. (4) Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil–Qiangtang, Tarim, and Qaidam.     

Isotopic Ages of the Penglai Group in the Jiaobei Belt and Their Geotectonic Implications

The Penglai Group in the Jiaobei Belt is the only remaining cover of the Archaean to Early Proterozoic crystalline basement in eastern Shandong. The ages of deposition of the Penglai Group and of its deformation and metamorphism have long been a subject of speculation. Whole-rock Rb-Sr ages, illite-whole-rock pair Rb-Sr ages and illite K-Ar ages recently obtained from the Penglai Group slates are reported and interpreted in this paper. On the basis of structural and metamorphic studies coupled with analyses of illite crystallinity, XRD and SEM , a whole-rock age of 473±32 Ma (Ordovician) is interpreted as the time of termination of burial metamorphism experienced by the Penglai Group. Therefore, the age of the Penghai Group is older than Ordovician. The first-phase folding and syntectonic low greenschist facies metamorphism in the Penglai Group, i.e. the Penglai Movement, took place before 299±4 Ma B.P., i.e in the Late Carboniferous. The Penglai Movement that occurred in the Jiaobei Belt on the south     

A Metallogenic Model of Gold Deposits of the Jiaodong Granite-Greenstone Belt

An analysis of trace elements and isotopic geochemistry suggest that the ore-forming materials of gold deposits in the Jiaodong granite-greenstone belt have multiple sources, especially the mantle source. Seismic wave, magnetic and gravity fields show that the crust-mantle structure and its coupling mechanism are the fundamental dynamic causes for the exchange and accumulation of materials and energy in the metallogenic system. Considering the evolution history of the structural setting, the tectono-metallogenic dynamics model of the area can be summarized as follows: (1) occurrence of the greenstone belt during the Archean-Proterozoic-the embryonic form of Au-source system; (2) stable tectonic setting in the Paleozoic-an intermittence in gold mineralization; (3) intensive activation and reformation of the greenstone belt in the Mesozoic-tectono-mineralization and tectono-diagensis; (4) posthumous structural activity in the Cenozoic-destruction of orebodies in the later stage. In the middle and late Ind     

Discussing the Oil-Control Effects of the North Latitudinal 38° Belt in Central Part of the Ordos Basin

<正>The Ordos Basin in the western part of the North China Craton is commonly believed to be a multi-controlled oilbearing basin.It is bounded by the Xing’an-Mongolian Orogen to the north,the Qingling Orogen to the south,the Lüliang mountain to the east and the Helanshan-Liupanshan mountain belt to the west.The interpretation of geophysical data reveals a latitudinal(38°)fault belt in the centre of the Ordos Basin,which controls the hydrocarbon generation,migration and accumulation in the basin.This study attempts to     

Distribution Characteristics of Sulfur and the Main Harmful Trace Elements in China’s Coal

To promote the rational development and use of clean coal resources in China, data on the regional and age distribution of sulfur, arsenic and other harmful elements in Chinese coal was broadly collected, tested for content, and analyzed. Coal in northwestern China is characterized by low to extremely low levels of sulfur; the coal of the Taiyuan Formation in northern China mainly has high-sulfur content; that of the Shanxi Formation is mainly characterized by low sulfur coal; and the Late Permian coal in southern China has overall higher sulfur content; other regions have low sulfur coal. The average content of harmful trace elements in the bulk of China＇s coal is similar to the corresponding content in the coal of the North America and the rest of the world, whereas the content of various elements （Hg, Sb and Se） is different in magnitude to the corresponding percentage in the crust. The average content of the elements Cr, Se, Co, Be, U, Br in Late Permian coal in S China ranks first in the country whereas the average content of Hg and CI in the coals of Late Carboniferous to Early Permian age in N China are the highest. The average content of Mn in Early and Middle Jurassic coal is higher in NW China. The high content of harmful elements in some coal should cause particular concern both in the development and utilization of coal.     

The Tectonic Implications of the Hongliuhe-Xichangjing Ophiolitic Mélanges Belt in the Central Region of the Beishan Orogen, NW China — Constrained by the U-Pb Ages of Detrital Zircons of the Metasandstones

The tectonic attributes of different blocks within orogenic belts are of great significance for the study of accretionary processes and the evolution of Earth. The Hongliuhe-Niujianzi-Baiyunshan-Xichangjing ophiolitic mélange belt(HXOMB) is distributed in the heart of the Beishan Orogen, the Shuangyingshan and Minshui-Hanshan blocks being distributed in the south and north of the HXOMB respectively, and a large number of Early Paleozoic geological units are exposed on the blocks. According to the zircon age populations of the metasandstones in the Baiyunshan area recovered in this paper, when compared with the zircon age populations of the Paleozoic metasandstones reported in the Niujuanzi and Hanshan areas, we found that the metasandstones of the Shuangyingshan Block have age peaks at c. 598 Ma, 742 Ma, 828 Ma, 941 Ma, 990 Ma, 1168 Ma, 1636 Ma, 2497 Ma with non-significant age populations of 1500–1300 Ma, showing a possible affinity with the Tarim Craton; the metasandstones of the Minshui-Hanshan Block have age peaks at c. 606 Ma, 758 Ma, 914 Ma, 1102 Ma, 1194 Ma, 1304 Ma, 1672 Ma with significant age populations of 1500-1300 Ma, showing a possible affinity with the Chinese Central Tianshan Block. Therefore, the HXOMB of the Beishan Orogen is of great significance in plate segmentation, which separates the Tarim Craton in the south and the Chinese Central Tianshan Block in the north. Based on the evolutionary process of the Hongliuhe-Xichangjing ocean in the Beishan Orogen, we believe that break-up and convergence can be recognized as having occurred twice between the Chinese Central Tianshan Block and the Tarim Craton since the Mesoproterozoic in the Beishan area. This was related firstly to the break-up of the Columbia Supercontinent and the convergence of the Rodinia Supercontinent, mainly during the Middle Mesoproterozoic to Early Neoproterozoic, and secondly to the opening and closing of the Hongliuhe-Xichangjing ocean, mainly during the Early Paleozoic.     

Proceedings of the Special Meeting of the Geological Society on the 3rd November, 1931. With a Half-tone Block of the Pictures of the Grabau Medal.

In opening the meeting, the chairman made the following address: "It is my agreable duty to announce and make the award of the Grabau Medal to two members of our Society, Drs. J. S. Lee and Davidson Black. "The Grabau Medal was founded in 1925 by Mr. C. Y. Wang. the then President of the Geological Society. It was so named in honor of Dr. Grabau     

A study on the environmental conditions of the microsparite （Molar-tooth） carbonates

Along with the progress in research on the Precambrian, Molar-tooth carbonates (simplified as MT, or microsparite carbonates or MT structure) which were formed in the Middle-Late Proterozoic have become a hot subject recently. The Proterozoic Molar-tooth (MT) carbonate rocks refer to those Meso- to Neoproterozoic (1600-650 Ma) carbonates with MT structure, i.e., a series of peculiar, ptygmatically folded and spar-filled cracks in fine-grained carbonates of Precambrian age, located in the environment of mid- to inner ramp and shallow platform. MTS, like a bridge connecting the inorganic world with the organic one, are closely related to the evolution of paleo-oceans, atmosphere and biosphere. Their development and/or recession are/is related to the origin of life and the abruption of sedimentary geochemistry events of marine carbonates. By using modern instruments and testing methods adequately, the contents of oxides in sandstones were measured and the REE distribution pattern curves were established; an accurate value of isotopic ratio of 87Sr/86Sr was obtained, that is, the age of MT formation is about 750-900 Ma; C and O isotopes of some fresh micrite limestone samples were analyzed; the energy spectrum analysis revealed that the MT consists mainly of microspar calcite, while as for its chemical composition, the matrix shows outstanding peaks of Ca, Mg, Al, Si, and K. The geochemical indicators proved that Neoproterozoic MT carbonates in the Jilin-Liaoning region were developed at the margin of a stable continent, in the torrid zone where the paleo-temperature was about 50℃, the seawater had normal salinity when MT was formed during the Wanlong period in southern Jilin and during the Yingchengzi and Xingmincun periods in eastern Liaoning. The sedimentary environment was located in the inner ramp. In summary, it is of great importance to understand the origin of MT, ascertain the paleo-climate and paleo-environment characteristics, constrain the age and the stratigraphic division and comparison of the Proterozoic so as to study the geochemical characteristics of MT carbonates and their formation environment.     

Variations and net transport of dissolved inorganic nutrients in the South Passage of the Changjiang （Yangtze River） Estuary

Dissolved inorganic nutrient elements were analyzed from the samples collected in the South Passage of the Changjiang (Yangtze River) Estuary in March 2003, including NH4 , NO3-, NO2- and PO43-. The water samples were collected with a Niskin sampler hourly at the near-surface, middle and near-bottom depths at the three stations -A1, A2 and A3-during two complete tidal cycles of neap tide and spring tide. Results showed that 1) the concentrations of NH4 , NO3- and NO2- were a little higher respectively during the neap tide than those during the spring tide, while PO43- showed an opposite trend, and each was higher in the ebb tide than in the flood tide, either for the neap tidal cycle or the spring tidal cycle; 2) higher stratification of the nutrients existed obviously in this area, with the concentrations of which increased from the bottom to the surface, especially for NH4 and NO3-; 3) the coefficient of variation (C.V.) values of all dissolved inorganic nutrients varied from 4.06% to 36.8% beyond different influences of the tidal current and Changjiang runoff; 4) with increasing suspended matter in the water column, the concentrations of PO43- became lower in the filtered water; and 5) the total transport of each tidal cycle was much more in the spring tide than in the neap tide, and the positive values indicated that the nutrients had been exported to the East China Sea. Studies on the variations and net transport of dissolved inorganic nutrients in the South Passage of the Changjiang Estuary will provide the scientific basis for the study of the mechanism of red tide in the East China Sea.     

U-Pb zircon age from the base of the Ediacaran Doushantuo Formation in the Yangtze Gorges,South China： constraint on the age of Marinoan glaciation

The reported new U-Pb age by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircon was obtained from a tuff sample at the basal Doushantuo Formation in the Jiuqunao section, which situated at the western limb of the Huangling anticline in the Yangtze Gorges in Zigui, Hubei, South China. Eighteen spots of zircons were analyzed and they form two clusters: one includes three spots, with an inherited age of 784+ 15 Ma (MSWD=0.05); the other consists of 15 spots and gives a weighted mean ^206pb/^238U age of 628.3&#177;5.8 Ma (MSWD=0.86). It is the first SHRIMP U-Pb zircon age obtained nearly the base of the Doushantuo Formation of Ediacaran and represents a maximum age of the Doushantuo Formation It also forms an age constraint on the upper limit age of the Nantuo (Marinoantype) glaciation.     

The Evolution of the Quaternary Salt Lakes in the Qaidam Basin

The paper discusses the distribution of Quaternary sediments, occurrence of saline minerals and phases of neotectonic movements and their manifestations in the Qaidam basin. The formation of four successive lacustrine terraces in Tertiary anticlinal zones in the western part of the basin was related to the neotectonic movements that took place 100 Ka ago, and the distribution of such terraces discloses, in a way. the evolutionary history of the Quaternary salt lakes. According to the distribution of the terraces coupled with the distribution of Quaternary sediments and features of salt deposition, four periods of Quaternary salt lake evolution in the basin may be distinguished, which correspond to four stages of salt deposition respectively.