Benthic foraminifera and bottom water evolution in the middle-southern Okinawa Trough during the last 18 ka

A piston sediment core E017 from the middle-southern Okinawa Trough was investigated. A preliminary study of the deep-water evolution since 18 cal. ka BP was performed based on the quantitative census data of benthic foraminiferal fauna, together with planktonic foraminiferal oxygen and carbon isotope, AMS(14)C dating, and the previous results achieved in the southern Okinawa Trough. The result shows that the benthic fauna was dominated by Bulimina aculeata (d'Orbigny), Uvigerina peregrina (Cushman), Hispid Uvigerina and Uvigerina dirupta (Todd) during the glaciation-deglaciation before 9.2 cal. ka BP, while Epistominella exigua (Brady), Pullenia bulloides (d'Orbigny), Cibicidoides hyalina (Hofker), Sphaeroidina bulloides (d'Orbigny) and Globocassidulina subglobosa (Brady) predominated the fauna in the post-glacial period after 9.2 cal. ka BP. The benthic foraminifera accumulation rate (BFAR), paleoproductivity estimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity and organic matter flux during the glaciation-deglaciation were higher than those of the post-glacial period in the middle-southern Okinawa Trough, and gradually enhanced from the southern to the central Okinawa Trough during the glaciation-deglaciation, which could be caused by the discrepancy of the terrigenous nutrients supply. High abundances of E exigua, an indicator of pulsed organic matter input, after 9.2 cal. ka. BP may indicate that the intensity of seasonally riverine pulsed flux during the post-glacial period was stronger than that of the glaciation-deglaciation period, and the seasonal influx in the central trough might be stronger than in the south. The temporal distributions of the typical species indicating bottom water oxygen content and ventilation condition show that the ventilation of the bottom water during the post-glacial period is more active than the glaciation-deglaciation, which reflects that the evolution of the intermediate and deep waters of the northwestern Pacific during the last glaciation has no evident influence on the deep-water of the middle-southern Okinawa Trough. Additionally, the variations in agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies indicate that carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough and rapidly enhanced at 9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 cal. ka BP.

Paleoceanographic records in the sedimentary cores from the middle Okinawa Trough

Two gravity piston cores (Cores 155 and 18) involved in this study were collected from the middle Okinawa Trough. Stratigraphy of the two cores was divided and classified based on the features of planktonic foraminifera oxygen isotope changes together with depositional sequence, millennium-scale climatic event comparison, carbonate cycles and AMS(14)C dating. Some paleoclimatic information contained in sediments of these cores was extracted to discuss the paleoclimatic change rules and the short-time scale events presented in interglacial period. Analysis on the variation of oxygen isotope values in stage two shows that the middle part of the Okinawa Trough may have been affected by fresh water from the Yellow River and the Yangtze River during the Last Glacial Maximum (LGM). The oxygen isotope value oscillating ranges of the cores have verified that the marginal sea has an amplifying effect on climate changes. The delta(13)C of benthic foraminifera Uvigerina was lighter in the glacial period than that in the interglacial period, which indicates that the Paleo-Kuroshio's main stream moved eastward and its influence area decreased. According to the temperature difference during the "YD" period existing in Core 180 and other data, we can reach the conclusion that the climatic changes in the middle Okinawa Trough area were controlled by global climatic changes, but some regional factors had also considerable influence on the climate changes. Some results in this paper support Fairbanks's point that the "YD" event was a brief stagnation of sea level rising during the global warming up procession. Moreover, the falling of sea level in the glacial period weakened the exchange between the bottom water of the Okinawa Trough and the deep water of the northwestern Pacific Ocean and resulted in low oxygen state of bottom water in this area. These procedures are the reasons for carbonate cycle in the Okinawa Trough area being consistent with the "Atlantic type" carbonate cycle.

The stability zone of gas hydrate in the slope of East China Sea and neighboring trough basin area

We analyze the distribution of temperature and heat flow of the sea floor sediment in the area of East China Sea slope and West basin area of the Okinawa Trough. Based on the Sonar Buoy and OBS data, 6 velocity layers are recognized, each of which has velocity of 1.8(1.8 similar to 2.2) km/s,2.2(2.0 similar to 2.5)km/s,2.8 (2.7 similar to 3.2)km/s,3.4 similar to 3.6km/s,4.2(4.1 similar to 4.7)km/s and 5.1km/s, respectively. The upper velocity layer of 1.8 similar to 2.2 km/s corresponds to the Quaternary sediment stratum. The layer with velocity 3.4 similar to 4.2km/s is the Pliocene sediment stratum. The area that is suitable for stable existence of gas hydrate by the temperature and pressure is 70,000km(2) about 1/10 the total area of East China Sea. The thickness of the stability zone ranges from 400m (Middle Part of Okinawa Trough) to 1100m (North and South Part of Okinawa Trough). The Quaternary and Pliocene layers are suitable for stable exitence of gas hydrate. According to the tectonic stability and heat flow, the north part and south part of the Okinawa Trough are the most perspective area for the gas hydrate explorations.

Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record

Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since similar to 18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at similar to 11.2 cal. kyr B.P. due to a rapid rise of sea level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bolling-Allerod (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5-9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3-4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough. (c) 2006 Elsevier B.V. All rights reserved.

Seismic profiles across the middle Tan-Lu fault zone in Laizhou Bay, Bohai Sea, eastern China

The stratigraphic architecture, structure and Cenozoic tectonic evolution of the Tan-Lu fault zone in Laizhou Bay, eastern China, are analyzed based on interpretations of 31 new 2D seismic lines across Laizhou Bay. Cenozoic strata in the study area are divided into two layers separated by a prominent and widespread unconformity. The upper sedimentary layer is made up of Neogene and Quaternary fluvial and marine sediments, while the lower layer consists of Paleogene lacustrine and fluvial facies. In terms of tectonics, the sediments beneath the unconformity can be divided into four main structural units: the west depression, central uplift, east depression and Ludong uplift. The two branches of the middle Tan-Lu fault zone differ in their geometry and offset: the east branch fault is a steeply dipping S-shaped strike-slip fault that cuts acoustic basement at depths greater than 8 km, whereas the west branch fault is a relatively shallow normal fault. The Tan-Lu fault zone is the key fault in the study area, having controlled its Cenozoic evolution. Based on balanced cross-sections constructed along transverse seismic line 99.8 and longitudinal seismic line 699.0, the Cenozoic evolution of the middle Tan-Lu fault zone is divided into three stages: Paleocene-Eocene transtension, Oligocene-Early Miocene transpression and Middle Miocene to present-day stable subsidence. The reasons for the contrasting tectonic features of the two branch faults and the timing of the change from transtension to transpression are discussed. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.

Sea surface temperature reconstruction for the middle Okinawa Trough during the last glacial-interglacial cycle using C-37 unsaturated alkenones

C-37 unsaturated alkenones were analyzed on a core retrieved from the middle Okinawa Trough. The calculated U-37(K') displays a trend generally parallel with those of the oxygen isotopic compositions of two planktonic foraminiferal species, Neogloboquadrina dutertrei and Globigerinoides sacculifer, suggesting that in this region, SST has varied in phase with global ice volume change since the last glacial -interglacial cycle. The U-37(K')-derived SST ranged from ca. 24.0 to 27.5 degrees C, with the highest value 27.5 degrees C occurring in marine isotope stage 5 and the lowest similar to 24.0 degrees C in marine isotope stage 2. This trend is consistent with the continental records from the East Asian monsoon domain and the marine records from the Equatorial Pacific. The deglacial increase of the U-37(K')-derived SST is similar to 2.4 degrees C from the Last Glacial Maximum to the Holocene. (c) 2007 Elsevier B.V. All rights reserved.

海拉尔盆地贝尔凹陷基岩潜山特征及储层预测

The lithology of the buried hill of Triassic Budate group in Beier depression is epimetamorphic clastic rock and volcanic clastic rock stratum. Recently the favorable hydrocarbon show was discovered in buried hill of base rock, and large-duty industrial oil stream was obtained in some wells in Beier depression. Based on the information of seismos and wells, the tectonic framework, tectonic deformation times and faulted system of the Beier depression are comprehensively studied, then configuration, evolutional history, genetic type and distributed regularity of buried hill are defined. According to observing description and analysis of core sample, well logging and interpretive result of FMI, the lithological component, diagenetic type and diagenetic sequence of buried hill reservoir are confirmed, then reservoir space system of buried hill is distinguished, and vegetal feature, genetic mechanism and distributed regularity of buried hill fissure are researched, at the same time the quantitative relationship is build up between core fissures and fissures interpreted by FMI. After that fundamental supervisory action of fault is defined to the vegetal degree of fissure, and the fissure beneficial places are forecasted using fractal theory and approach. At last the beneficial areas of Budate group reservoir are forecasted by reservoir appraisal parameters optimization such as multivariate gradually regression analysis et. al. and reservoir comprehensive appraisal method such as weighing analyze and clustering procedure et. al. which can provide foundation for the next exploratory disposition. Such production and knowledge are obtained in this text as those: 1. Four structural layers and two faulting systems are developed, and four structural layers are carved up by three bed succession boundary surfaces which creates three tectonic distortional times homology. Three types of buried hill are divided, they are ancient physiognomy buried hill, epigenetic buried hill, and contemporaneous buried hill. 2. Reservoir space of Budate buried hill is mainly secondary pore space and fissure, which distributes near the unconformity and/or inside buried hill in sections. The buried hill reservoir experienced multi-type and multi-stage diagenetic reconstruction, which led to the original porosity disappeared, and multi secondary porosity was created by dissolution, superficial clastation and cataclasis et. al. in diagenetic stage, which including middle crystal pore, inter crystal pore, moldic pore, inter particle emposieu, corrosion pore space and fissure et. al. which improved distinctly reservoir capability of buried hill. 3. The inner reservoir of buried hill in Beier depression is not stratigraphic bedded construction, but is fissure developing place formed by inner fault and broken lithogenetic belt. The fissures in inner reservoir of buried hill are developed unequally with many fissure types, which mainly are high angle fissure and dictyonal fissures and its developing degree and distribution is chiefly controlled by faulting. 4. The results of reservoir comprehensive evaluate and reservoir predicting indicates that advantageous areas of reservoir of buried hill chiefly distributes in Sudeerte, Beixi and Huoduomoer, which comprehensive evaluate mainly Ⅱand Ⅲ type reservoir. The clues and results of this text have directive significance for understanding the hydrocarbon reservoir condition of buried hill in Beier depression, for studying hydrocarbon accumulated mechanism and distributed regularity, and for guiding oil and gas exploration. The results of this text also can enrich and improve nonmarine hydrocarbon accumulated theory.

东天山红山高硫型浅成低温铜-金矿床氧化带的形成机理和硫酸盐矿物的系列发现及意义

Located in the Paleozoic uplift along the southern margin of Tu-Ha basin in eastern Xinjiang, the newly discovered Hongshan Cu-Au deposit occurs in the superimposed Mesozoic volcanic basin upon the north section of later Paleozoic Dananhu-Tousuquan accretionary arc. Kalatage Cu-Au orebelt is controlled by NWW-trend faults, and includes Hongshan and Meiling Cu-Au deposits. The host rocks of Hongshan ore district are mainly rhyolitic-dacitic ignimbrites, whereas Cu-Au mineralization is closely related to quartz porphyry, rhyolitic porphyry and granitic porphyry. Mineralization styles are dominantly veinlet-disseminated and veinlet, occasionally stockwork. The mineral association is chalcopyrite, pyrite, bornite, chalcocite and sphalerite. The hydrothermal alteration consists of silicfication, sericitization, alunitization, pyrophylitization, illitization, hydromuscovitization, and chloritization. Hongshan Cu-Au deposit, on the edge of the desert, is one of the driest areas in eastrn Tianshan. Moreover， the highest temperature has been up to 60℃, and the average rainfall receives only 34.1mm/y. The light rainfall and rapid evaporation in the vicinity of this deposit have allowed the formation of a great variety of water-soluble sulfates. Oxidization zone of this deposit lies on the upper part of primary sulfide orebodies appearing with a depth of 50-60m, which is dominant in sulfate minerals. 1. Based on the field observation, the volcanic and sub-volcanic rock composition, hydrothermal alteration, ore structure and mineralization characteristics, this paper proposed that the Hongshan Cu-Au deposit belongs to a transitional type from high-sulfide epithermal to porphyry Cu-Au deposit, which corresponds with the typical HS-epithermal deposit such as Zijinshan Au-Cu deposit in Fujian Province, SE-China. 2. The Hongshan copper-gold deposit was controlled by the tectonic, stratum, magma activity and volcanic apparatus, whereas Au mineralization is closely related to quartz porphyry, rhyolitic porphyry and fine grained pyritization in hydrothermal activity, and Cu mineralization is closely related to quartz porphyry and hydrothermal explosive breccia. 3. Oxidation zone of Hongshan Cu-Au deposit lies on the upper part of primary sulfide orebodies deposit. 23 sulfate minerals were identified in this work. The results of samples XRD and chemical analysis were furthermore confirmed through thermal, infrared spectrum and mössbauer spectrum analysis. Among those, nine minerals as Ferricopiapite, Cuprocopiapite, Rhomboclase, Parabutlerite, Krausite, Yavapaiite, Metasideronatrite Kroehnkite and Paracoquimbite were founded in China for the first time. And Paracoquimbite was secondly reported in the world (first case reported at 1938 in Chile). 4. EPMA analysis shows that Al impurity in crystal lattice is important to polytype formation of paracoquimbite and coquimbite besides stack fault. 5. Compared with Meiling Cu-Au deposit in the same Kalatage ore belt from the characteristics of δ34S of barite, lithofacies, hydrothermal alteration and homogeneous temperature, Hongshan Cu-Au deposit belongs to the same metallogenic system of HS-epithermal type as Meiling Cu-Au deposit. But Hongshan Cu-Au deposit has less extensive alteration and shallower denudation. 6. Sulfur isotope analyses show that δ34S values of pyrites vary in the range of +1.86‰~+5.69‰, with an average of 3.70‰, mostly in the range of +1.86‰~+3.20‰, and δ34Scp<δ34Spy. Therefore ore-forming fluid of porphyry comes from mantle and was contaminated by the earth’s crust. Sulfur isotope has reached balance in ore-forming process. 7. Sulfur isotope analyses show that δ34S values of sulfates vary in the range of +2.15‰~+6.73‰, with an average of +3.74‰, mostly equals as δ34S values of primary sulfides in Hongshan Cu-Au deposit. So supergene sulfates inherit sulfur of primary sulfide. δ34S values are mostly same in different sulfates. As well as pyrite and chalcopyrite, volcanic hot spring and associated native sulfur underground also provide water medium and sulfur during the formation process of sulfate. 8. According to the EPMA of sample chalcopyrite and pyrite in Hongshan Cu-Au, the value of Cu/Ni is 0.98-34.72, mostly close to the value of 5, which shows that Hongshan deposit is a typical volcanogenic magmaic hypothermal deposit. Au and Ag, Zn, Te and Bi are positive correlation, Cu and Hg, Se, Sb are positive correlation, indicates Au and Cu don’t locate in the factor of mineralization of same mineralization groups. The reasons of gold concentration in the oxidation zone are: 1). Change of redox potential (Eh) makes gold to deposit from the liquid of mineralization zone; 2). PH is one of the most factors of gold’s deposition; 3). Soluble complex and colloid of gold can be adsorbed easily. 9. The biotite and hornblende K-Ar isotopic ages from the wall rock－quartz diorite, biotite granite and monzonite granite are 231.99±3.45Ma, 237.97±2.36Ma and 296.53±6.69Ma respectively. The ore-bearing rhyolitic breccia lava contains breccia of the biotite granite which indicates the volcanism and related Cu-Au mineralization occurred later than the granite, possibly in Mesozoic. K-Ar ages of granitoids in Sanya, Baishiquan and Hongliugou area and Molybdenite Re-Os age of Baishan Mo deposit all are in Triassic. Besides late Paleozoic magmatism, igneous magmatic event of Mesozoic was widespread in eastern Tianshan. 10. The K-Ar age dating indicates that the K-Ar age of Voltaite occurred below surface 1m is 56.02±3.98Ma, K-Ar age of Ferricopiapite occurred below surface 1.5m is 8.62±1.12Ma, K-Ar age of Yavapaiite occurred below surface 14 m is 4.07±0.39Ma, and K-Ar age of Voltaite occurred below surface 10 m is 14.73±1.73Ma. So the age interval of oxidation zone of Hongshan copper-golden bed is between 60 -3.38Ma. Oxidization occurred at Caenozoic era (from 65Ma), which can be identified through comparing with different deposits oxidation zone in other countries. The coupling between global tectonic event and climatic change event which occur from Caenozoic era has some effect on epigeosphere system, which can act on the surface of bed oxidation zone similarly. It induces that the age mentioned above coincide with collision of India-Asia and multistage uplifting of Qinhai-Tibet Plateau happened subsequently. Bed oxidation zone is the effect and record of collision and uplifting of Tibet Plateau. The strong chemical weathering of surface accumulation to which was leaded by PETM event occurred Paleocene and Eocene is the reason of Voltaite sharply rises. On the contrary, Ferricopiapite formed due to the global cold weather. The predecessor did much research through biota, isotopes, susceptibility, but this paper try to use different sulfate mineral instead of climatic change. So the research of sulfate minerals not only indicates a great deal of oxidized zone feature, but also the intergrowth of sulfate minerals may be used to trace paleoenviroment and paleoclimate of oxidation zone. 11. Analysis of the information of alteration and mineralization features of four bore cores, induced activity polarization well logging and Eh-4 geophysical section, deep mineralization anomaly objects of Hongshan ore districts shows low resistance, middle and high polarization, measurements of Eh-4 consecutive conductance section show the existing of concealed porphyry ore body deeper than 450m, on the top of and around rock body there are low resistance body ranged from 100-300Ω•m, this area may be the ore-bearing part. In a word, Hongshan Cu-Au deposit deposit is a combine of upper HS-style epithermal Au deposit and deeper porphyry mineralization system. It has great potential to find large HS-style epithermal-porphyry Au-Cu deposits. This paper consists of seven chapters and twenty seven sections. The geological character of deposit is basic condition in this work. Constitute of oxidation zone, research of sulfate mineral, relation between oxidation and primary zone, K-Ar ages of potassic sulfate are key parts of thesis. Genesis of ore deposit is the further expansion of this research. Analysis of ore-controlling factors is the penetration above basic. Analysis of potential is application of exploration.

松辽盆地南部岩性油藏成藏模式与分布规律

According to the basic geologic conditions, the paper is directed by the modem oil-gas accumulation theory and petroleum system in which typical oil pools are analyzed and the shape of lithologic trap and geologic factors are pointed out. The process during which oil and gas migrate from source rock to lithologic trap is rebuilt, and the accumulation model of oil pool is set up. With the comprehensive application of seismic geologic and log data and paying attention to the method and technology which is used to distinguish lithologic accumulation. Promising structural-lithofacies zones are got and the distribution rule of various lithologic accumulation is concluded. With making use of the biologic mark compound, different reservoirs are compared. As a result, the oil and gas in HeiDimiao come from Nenjiang Group's source rocks; in SaErTu from QingShenkou Group's and Nenjiang Group's, and in PuTaohua. GaoTaizi and FuYang from QingShankou Group's. According to the development and distribution of effective source rock, oil distribution and the comparison in the south of SongLiao basin, the characteristic of basin structure and reservoir distribution is considered, and then the middle-upper reservoir of SongLiao basin south are divided into two petroleum system and a complex petroleum system. Because of the characteristic of migration and accumulation, two petroleum systems can furtherly be divided into 6-7 sub-petroleum systems,20 sub-petroleum systems in all. As a result of the difference of the migration characteristic, accumulation conditions and the place in the petroleum system, the accumulation degree and accumulation model are different. So three accumulation mechanism and six basic accumulation model of lithologic trap are concluded. The distribution of lithologic pools is highly regular oil and gas around the generation sag distribute on favorable structural-lithofacies zones, the type of lithological pool vary regularly from the core of sandstone block to the upper zone. On the basic of regional structure and sedimentary evolution, main factors which control the form of trap are discovered, and it is the critical factor method which is used to discern the lithologic trap. After lots of exploration, 700km~2 potential trap is distinguished and 18391.86 * 10~4 tons geologic reserves is calculated. Oil-water distribution rule of pinch-out oil pool is put up on plane which is the reservoirs can be divided into four sections. This paper presented the law of distribution of oil and water in updip pinch-out reservoir, that is, hydrocarbon-bearing formation in plane can be divided into four zones: bottom edge water zone, underside oil and water zone, middle pure oil zone and above residual water zone. The site of the first well should be assigned to be middle or above pure oil zone, thus the exploration value of this type of reservoir can be recognized correctly. In accordance with the characteristics of seism and geology of low permeability thin sandstone and mudstone alternation layer, the paper applied a set of reservoir prediction technology, that is: (1)seism multi-parameter model identification; (2) using stratum's absorbing and depleting information to predict reservoir's abnormal hydrocarbon-bearing range. With the analysis of the residual resource potential and the research of two petroleum system and the accumulation model, promising objective zones are predicted scientifically. And main exploration aim is the DaRngZi bore in the west of ChangLin basin, and YingTai-SiFangZi middle-upper assembly in Honggang terrace.

黄土中主要温室气体组分特征

Scientists have paid much attention to the greenhouse effects and the greenhouse gases for the fact of global warming. There are many uncertainties in the prediction of future climatic change. One of the important reasons causing the uncertainties is insufficient researches of the sources and sinks of greenhouse gases, especially, there is a missing sink in the global carbon cycle. The recent researches proposal that there may be an important carbon sink in the middle-latitude terrestrial ecosystems (vegetation and soil) in the North Hemisphere, despite that there is much disputation about its position and amplitude. Chinese loess is located in the middle latitude area in the North Hemisphere, what kind of role does it play in and how does it influence on the balance of the global greenhouse gases budget? For this reason, many samples were taken and analyzed from wide range and multi-stratum of Chinese loess to understand characteristics of major greenhouse gases in loess and loess possible effect on global greenhouse gas budget. Using self-made spiral corer, we totally took 81 gas samples and 65 soil samples from 7 loess profiles in China such as Zhaitang loess section of Beijing, Pianguan, Xingxian, Lishi, Puxian, Jishan loess section of Shanxi Province, and Luochuan loess section of Shaanxi Province. The gas concentrations for CO_2, CH_4 and N_2O, the contents of N_2, O_2 and carbonate, and the carbon isotopic compositions of CO_2 and carbonate in loess strata sequences are observed and measured. In addition, 19 gas samples data of the Weinan loess section, Shaanxi Province are combination with this research to study characteristics of greenhouse gases in loess. This research indicates that (1) the free gases in loess are neither paleo-atmospheric gases nor modern atmospheric gases; (2) the concentrations of CO_2, CH_4 and N_2O in loess are higher than atmospheric level; (3) the δ~(13)C of loess CO_2 shows that the CO_2 in loess mainly comes from the oxygenolysis of organic matters, but because of isotopic exchange with carbonate in loess, the carbon isotopic exchange with carbonate in loess, the carbon isotopic compositions of loess CO_2 are much more heavier than organic original CO_2; (4) the concentration of CH_4 in Malan loess is lower because it is not favorable for the decomposition of anaerobic bacteria in the Malan Loess; (5) estimation of the total amount of the carbonate in loess reveals that loess is a huge carbon reservoir (about 850PgC). In addition, the impact of the deuterogenic carbonatization during the loess accumulation on the global carbon cycle was discussed, and the preliminary conclusion is that the research work is still not enough to evaluate the effect of loess on the sources and sinks of the anthropogenic CO_2.

沾化凹陷火成岩油气藏形成条件和分布规律研究

As a kind of special lithologic ones, Igneous rock oil and gas pool is more and more paid attention, and it has different forming condition and distribution from conventional ones, such as various terrane distribution types, serious reservoir anisotropy, complicated hydrocarbon-bearing, so there is not successful experience to follow for exploration and development of this complex subtle oil and gas pool at present. For an example of Igneous oil and gas pool of Luo151 area in Zhanhua seg, Eastern China, this article study the difficult problem, including petrologic nd lithofacies analysis, Origin, invasion age and times of Igneous rock, reservoir anisotropy, Geological Modeling, Igneous reservoir synthesis evaluation. forming condition and distribution are studied synthetically, and an integrated method to predict igneous rock oil and gas pool is formed, which is evaluated by using development data. The Igneous rock is mainly diabase construction in Luo151 area of Zhanhua Sag, and petrologic types include carbonaceous slate, hornfels, and diabases. Based on analyzing synthetically petrologic component, texture and construct, 4 lithofacies zones, such as carbonaceous slate subfacies, hornfels subfacies containing cordierite and grammite, border subfacies and central subfacies, are divided in the diabase and wall rock. By studying on isotopic chronology, terrane configuration and imaging logging data, the diabase intrusion in Zhanhua Sag is formed by tholeiite magma emplacing in Shahejie formation stratum on the rift tension background Lower Tertiary in North China. The diabase intrusion of Luo151 is composed possibly of three periods magma emplacement. There is serious anisotropy in the diabase reservoirs of Luo151 in Zhanhua Sag. Fracture is primary reservoir space, which dominated by tensile fracture in high obliquity, and the fracture zones are mainly developed round joint belt of igneous rock and wall rock and position of terrane thickness changing rapidly. The generation materials of the reservoirs in Luo151 igneous oil pools consist of Intergranular micropore hornfels, condensate blowhole-solution void diabase condensate edge, the edge and center of the condensate seam diabase, of which are divided into horizontal, vertical and reticulated cracks according fracture occurrence. Based on the above research, a conceptual model of igneous rock reservoir is generated, which is vertically divided into 4 belts and horizontally 3 areas. It is built for the first time that classification evaluation pattern of igneous rock reservoir in this area, and 3 key wells are evaluated. The diabase construction is divided into grammite hornfels micropore type and diabase porous-fracture type reservoirs. The heavy mudstone layers in Third Member of Shahejie formation (Es3) provide favorable hydrocarbon source rock and cap formation, diabase and hornfels belts serve as reservoirs, faults and microcracks in the wall rocks as type pathways for oil and gas migration. The time of diabase invasion was about in the later deposition period of Dongying Formation and the middle of that of Guantao Formation, the oil generated from oil source rock of Es3 in the period of the Minghuazhen formation and is earlier more than the period of diabase oil trap and porous space forming. Based on geological and seismic data, the horizon of igneous rocks is demarcated accurately by using VSP and synthetic seismogram, and the shape distribution and continuity of igneous rocks are determined by using cross-hole seismic technology. The reservoir capability is predicted by using logging constraining inversion and neural network technology. An integrated method to predict igneous rock oil and gas pool is formed. The study is appraised by using development data. The result show the reservoir conceptual model can guide the exploration and development of oil pool, and the integrated method yielded marked results in the production.

塔里木盆地塔中地区寒武-奥陶系烃源岩古地温及成烃演化史研究

The present maturity of Cambrian and Ordovician source rocks in Tazhong area, Tarim basin, is studied using several organic petrology methods and conodont CAI method. The highest palaeotemperature that the Cambrian-Ordovician undergone is revealed by Laser Roman Microprobe (LRM) analysis and by simulating experiment of the kerogen chemical kinetics. In according to all above study, the thermal history of Cambrian and Ordovician is reconstructed based on numerical simulating approaches. The characteristics of secondary hydrocarbon generating are studied by inclusions analysis. The reflectances of the samples in the drills located in Tazhong area show that the maturities of Cambrian source rocks are in the stages of condense oil-dry gas, and that of Ordovician source rocks range from peak of oil generating to wet gas stage. The palaeotemperature data of Cambrian-Orovician source rocks from well Tacan 1, based on LRM analysis, are in coincidence with that from other methods. Also are the palaeotemperature data of Cambrian-Orovician source rocks in well Tacan 1 based on the simulating experiments of kerogen pyrolysis, similar to the homogenization temperatures of inclusions in the source rocks. Aaccording to the vitrinite inflectance data of the TZ12 well and Tacan 1 well, the paleotemperature gradients are analysized and reconstructed. These data show that the paleotemperature gradient in Tazhong area was the highest during Cambrian-Ordovician period, it was up to 3.5°C/100m. Following, the temperature gradient descended gradually and it reached to the lowest at present (2.2°C/100m). The histories of maturation and hydrocarbon generation of Cambrian and Ordovician source rocks in Tazhong area are researched systematically and quantitatively, the results show that periods of oil generation from Cambrian and Ordovician source rocks lasted for a long time from Ordovician to Carbonferious periods because the central Cambrian stratum in the north slope of Tazhong area is buried differently in depth. The top of the Cambrian entered into the peak of oil generation in middle-late Ordovician, and most area of the north slope of Tazhong area entered into the peak of oil generation in Carbonferious period, and on the uplift belt some of source rocks entered into the peak of oil generation in Permian period. In early Devonian, the central of the Lower Ordovician source rocks near the Manjiaer depression reached the peak of oil generation and near the top of the Tazhong uplift did not reached the peak of oil generation until early Cretaceous. The middle-upper Ordovician entered into the peak of oil generation in early-middle Jurassic. The time of the middle-upper Ordovician in the top of the uplift belt entering into the peak of oil generation was delayed, because the source rock was buried shallowly, and it did not reached the peak of oil generation until middle Cretaceous. Middle-upper Ordovician in the top of the north slope has been in the peak of oil generation now, it is consistent with the maturity (1.0-1.2%Ro) of the source rocks. The characteristics of the inclusions formed by kerogens are different from that by crystal-enclosed organic matters(OM) during secondary hydrocarbon generation of Cambrian and Ordovician source rocks. The secondary hydrocarbon generation mainly occurred in Mesozoic-Cenozoic period, in an area of about 9000km2 in the north slope. The intensity of the secondary hydrocarbon generation of Cambrian and Ordovician is up to 21kg/torg and 36kg/torg) respectively. Using the staged gas chromatography, the high-over maturated carbonate source rocks are analysized to release the adsorbed OM, inclusions OM and crystal-enclosed OM, respectively, and to evaluate their relative contributions to secondary hydrocarbon generation. The three periods of oil and gas migration and petroleum pools formation in Tazhong area are determined according to organic inclusions and solid bitumen.