A double-halocline structure in the Canada Basin of the Arctic Ocean

A year-round halocline is a particular hydrographic structure in the upperArctic Ocean. On the basis of an analysis of the hydrographic data collected in the Arctic Ocean, itis found that a double-halocline structure exists in the upper layer of the southern Canada Basin,which is absolutely different from the Cold Halocline Layer (CHL) in the Eurasian Basin. ThePacific-origin water is the primary factor in the formation of the double-halocline structure. Theupper halocline lies between the summer modification and the winter modification of thePacific-origin water while the lower halocline results from the Pacific-origin water overlying uponthe Atlantic-origin water. Both haloclines are all the year-round although seasonal and interannualvariations have been detected in the historical data.

Petrological Characteristics and Genesis of the Central Indian Ocean Basin Basalts

The Central Indian Ocean Basin （CIOB） basalts are plagioclase-rich, while olivine and pyroxene are very few. The analyses of 41 samples reveal high FeOT （～10-18 wt%） and TiO 2 （～1.4-2.7 wt%） indicating a ferrobasaltic composition. The basalts have high incompatible elements （Zr 63-228 ppm; Nb ～1-5 ppm; Ba ～15-78 ppm; La ～3-16 ppm）, a similar U/Pb （0.02-0.4） ratio as the normal midoceanic basalt （0.16±0.07） but the Ba/Nb （12.5-53） ratio is much larger than that of the normal midoceanic ridge basalt （～5.7） and Primitive Mantle （9.56）. Interestingly almost all of the basalts have a significant negative Eu anomaly （Eu/Eu＊=0.78-1.00） that may have been a result of the removal of feldspar and pyroxene during crystal fractionation. These compositional variations suggest that the basalts were derived through fractional crystallization together with low partial melting of a shallow seated magma.

Physical Properties,Morphology and Petrological Characteristics of Pumices from the Central Indian Ocean Basin

About 400 pumice clasts collected from the Central Indian Ocean Basin（CIOB）were studied for their morphology and were classified based on their shape and size.A majority of the samples range between1 cm and 36 cm and in the Zinggs shape diagram plot in the equant and oblate fields.The Corey Shape Factor for most of the samples is close to 0.7,which is common for volcaniclastic material. The physical properties such as density,specific gravity,void ratio,porosity,moisture content and degree of saturation,were determined for 30 pumice samples.Density varies from 0.21 to 0.74 g/cm^3 specific gravity 1.84 to 3.27,void ratio 2.21 to 10.67,porosity 67%to 91%,moisture content during sinking 0.44 to 2.35 and degree of saturation varies from 26.5%to 86%.Binocular and electron microscopy studies reveal that 60%of the vesicles are elongated,30%are spherical and 10%are fibrous.Petrography of the pumices exhibits vitrophyric texture with phenocrysts of feldspars and clinopyroxenes.X-ray diffractrogram and mineral analyses confirm plagioclase to be a major phase, while quartz and orthoclase are not uncommon.Todorokite is commonly present in the ferromanganese oxide coating present over some of the pumices.This paper also delves into some details concerning the controversial origin of the pumices and glass shards in the CIOB.

Role of the Oceanic Channel in the Relationships between the Basin/Dipole Mode of SST Anomalies in the Tropical Indian Ocean and ENSO Transition

The relationships between the tropical Indian Ocean basin （IOB）/dipole （IOD） mode of SST anomalies （SSTAs） and ENSO phase transition during the following year are examined and compared in observations for the period 1958-2008. Both partial correlation analysis and composite analysis show that both the positive （negative） phase of the lOB and IOD （independent of each other） in the tropical Indian Ocean are possible contributors to the E1 Nino （La Nifia） decay and phase transition to La Nifia （El Nifio） about one year later. However, the influence on ENSO transition induced by the IOB is stronger than that by the IOD. The SSTAs in the equatorial central-eastern Pacific in the coming year originate from subsurface temperature anomalies in the equatorial eastern Indian and western Pacific Ocean, induced by the IOB and IOD through eastward and upward propagation to meet the surface. During this process, however the contribution of the oceanic channel process between the tropical Indian and Pacific oceans is totally different for the IOB and IOD. For the IOD, the influence of the Indonesian Throughflow transport anomalies could propagate to the eastern Pacific to induce the ENSO transition. For the IOB, the impact of the oceanic channel stays and disappears in the western Pacific without propagation to the eastern Pacific.

Differences in nitrous oxide distribution patterns between the Bering Sea basin and Indian Sector of the Southern Ocean

Nitrous oxide （N2O） distribution patterns in the Bering Sea basin （BSB） and Indian Sector of the Southern Ocean （ISSO） were described and compared. In both sites, the waters were divided into four layers： surface layer, subsurface layer, N2O maximum layer, and deep water. Simulations were made to find out the most important factors that regulate the N2O distribution patterns in different layers of both sites. The results showed that in the surface water, N2O was more understaturated in the ISSO than the BSB. This phenom- enon in the surface water of ISSO may result from ice melt water intrusion and northeastward transport of the Antarctic surface water. Results of the rough estimation of air-sea fluxes during the expedition were （-0.34±0.07）-（-0.64±0.13） μmol/（m2·d） and （-1.47±0.42）-（-1.77±0.51） μmol/（m-2·d） for the BSB and the ISSO, respectively. Strongly stratified surface layer and temperature minimum layer restricted exchange across the thermocline. The N2O maximum existed in higher concentration and deeper in the BSB than the ISSO, but their contribution to the upper layer by eddy diffusions was negligible. In deep waters, a concentration difference of 5 nmol/L N2O between these two sites was found, which suggested that N2O production occurred during thermohaline circulation. N2O may be a useful tracer to study important large-scale hydrographic processes.

Evolution of the Extensional Rifted Yunnan-Guizhou-Guangxi Oceanic Basin During the Late Hercynian to Middle Indosinian Stage

On the basis of exhaustive researches on the facies sequences and depositlonal evolutionary process of various depositional systems, the genetic stratigraphic framework of the extensional rifted oceanic basin, which has undergone strong structural destruction, has been reconstructed by means of dynamic genetic stratigraphic analysis. Five depositional episodes have been distinguished from various isochronous stratigraphic boundaries and stratigraphic sequences with the three-dimensional structure of each depositional episode analysed in detail. The tectonic paleogeographic environment corresponding to different stages of each depositional episode has been reconstructed for individual depositional system tracts. And the evolution history of this rifted basin has been divided into four stages' initial rifting and oceanization of continental crust, stretching and spreading of the basin, subduction and basin differentiation, and convergence and collision. A NNE-trending intracontinental soft collision suture was left after the closing of the basin.

Early Palaeozoic Evolution of the Zhen' an- Xichuan Block and the Small Qinling Multi-Island Ocean Basin

Based on studies of palaeogeography, palaeobiogeography, palaeomagnetism, geochemistry and volcanism, this paper proposes that the Zhen'an-Xichuan area was a small Early Palaeozoic block rifted away from South Qinling and suturing onto North Qinling earlier than the other parts of South Qinling. In the Early Palaeozoic Qinling was a small archipelagic ocean basin with 5 rows of islands including the Zhen'an-Xichuan block. The drifting of the Yangtze and North China plates and the islands between them in the same direction at different speeds caused their suturing process to be different from the classic plate collision, which is the major feature of the suturing of the multi-island Tethys ocean basin. This also explains the problem that the Caledonian collision did not result in orogeny in eastern Qinling.

Paleoceanographic records in the Chukchi Basin, western Arctic Ocean during the late Quaternary

The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quan- titative studies of foraminiferal abundance, ice-rafted detritus （IRD） and its mineralogical and petrological compositions, planktonic Neogloboquadrina pachyderma （sin.） （Nps）-δ18O and -δ13C, biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Sec- ond Chinese National Arctic Expedition cruise. Seven IRD events appeared at MIS 7, 5, 3 and 1. These IRD were carried in massive icebergs, which were exported to the Beaufort Sea through the M＇Clure Strait Ice Stream, Canadian Arctic Archipelago, and then transported into the Chukchi Basin by the Beaufort Gyre. Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre, while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition. Therefore, the IRD events not only indicate the provenance of coarser detritus and ice export events, but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet. Seven light Nps-δ18O and -δ13C excursions could respond to enhanced rates of sea ice formation resulting in the pro- duction and sinking of isotopically light brines, but was irrelevant to the warm Atlantic water and freshwater inputs. Whereas, the heavy Nps-δ18O and -δ13C values separately reflect the lessened Arctic freshwater and Pacific water, and well-ventilated surface water from the continental shelf and halocline water. Variations of CaCO3 content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water, while the total organic carbon （TOC） and opal contents increased and decreased during the glacial and interglacial periods, respectively, which could be related to the TOC degradation, opal dissolution and redox conditions of interface between the bottom water and sediments.

Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major,trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types(siliceous,red clay and their transition zone)in the Central Indian Ocean Basin(CIOB)to address their genetic aspects,classification,growth rate,nature of host sediments and influence of REE in the processes of nodule formation.The nodules from CIOB are mostly either hydrogenetic(metals coming from oxygenated bottom water)and diagenetic(metals coming from suboxic sediment pore water)or a combination of both,depending on the source of supply of metal.However,a number of biogeochemical processes mediate this supply of metals which again changes from time to time,making the nodule growth process highly dynamic.This study suggests that at the initial stage of nodule growth,host sediments do not play much role in controlling the growth processes for which REEs can enter both Mn and Fe oxyhydroxide phases equally.Thus,the bottom water signature is imprinted in these early formed nodules irrespective of their host sediment substrate but with gradual growth and burial in the sediment,the main mode of metal enrichment becomes diagenetic through sediment pore water.This tends to increase the concentration of Mn,Ni and Cu over other elements which are retained in the sediment fraction.Among the REEs,Ce concentration of the nodules shows significant positive anomaly due to variation in redox potential and hence its magnitude can be used to get an idea about the metal enrichment procedure and the genetic type of the nodules.However,based on host sediment only,not much difference is found in the magnitude of Ce anomaly in these nodules.On the other hand,discrimination diagram,based on HFSE and REY chemistry,indicates that most of these nodules are of diagenetic origin under oxic condition with a trend towards hydrogenetic field.Further,the genetic type of the ferromanganese nodules from the CIOB are more effectively differentiated by a combination of their major and trace element concentrations rather than solely based on their REE or HFSE chemistry or host sediment substrate.

Terrestrial records of the early Albian Ocean Anoxic Event:Evidence from the Fuxin lacustrine basin,NE China

The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify terrestrial records of the early Albian OAE 1 b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted,including thick, organic-rich black mudstones, total organic carbon(TOC), organic carbon isotopes(d13 Corg), mercury concentration(Hg) and results from pyrolysis analyses(S2, Tmaxand HI). Results show three distinct short-term negative d13 Corgexcursions corresponding with relatively high TOC values,which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE1 b. Atmospheric CO2 concentration(p CO2) recovered from C3 plant d13 Corgcompositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of p CO2 corresponding to the three sub-events of OAE 1 b at this time interval. We infer that a trend of increasing p CO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices(CIA, WIP and MIA(O)) show an increasing trend during the OAE 1 b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses(HI vs. Tmaxand S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1 b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.

Velocity structure in the South Yellow Sea basin based on first-arrival tomography of wide-angle seismic data and its geological implications

The South Yellow Sea basin is filled with Mesozoic-Cenozoic continental sediments overlying pre-Palaeozoic and Mesozoic-Palaeozoic marine sediments.Conventional multi-channel seismic data cannot describe the velocity structure of the marine residual basin in detail,leading to the lack of a deeper understanding of the distribution and lithology owing to strong energy shielding on the top interface of marine sediments.In this study,we present seismic tomography data from ocean bottom seismographs that describe the NEE-trending velocity distributions of the basin.The results indicate that strong velocity variations occur at shallow crustal levels.Horizontal velocity bodies show good correlation with surface geological features,and multi-layer features exist in the vertical velocity framework(depth:0–10 km).The analyses of the velocity model,gravity data,magnetic data,multichannel seismic profiles,and drilling data showed that high-velocity anomalies(>6.5 km/s)of small(thickness:1–2 km)and large(thickness:>5 km)scales were caused by igneous complexes in the multi-layer structure,which were active during the Palaeogene.Possible locations of good Mesozoic and Palaeozoic marine strata are limited to the Central Uplift and the western part of the Northern Depression along the wide-angle ocean bottom seismograph array.Following the Indosinian movement,a strong compression existed in the Northern Depression during the extensional phase that caused the formation of folds in the middle of the survey line.This study is useful for reconstructing the regional tectonic evolution and delineating the distribution of the marine residual basin in the South Yellow Sea basin.

Formation of the Neoproterozoic Rifting Depression Groups of the Tarim Basin and its Hydrocarbon Potential: Responded to the Initial Opening of the Proto-Tethy Ocean

The largest and superimposed Tarim basin developed on the one of the three bigger craton, Tarim Craton, in China.The early Paleozoic is the heyday of its development and cratonization, and then changes to the different property basin. The reserved sedimentary strata of Neoproterozoicare recognized mainly in the local of outcrops periphery orogenic belts, but drilling core in the basin reveals them seldom. The proto-type of the initial Tarim Basinis always a mystery. The vast desert, hugethickness of sedimentary strata, multiple tectonic movements, and a low quality of deep data are the keys to getting to know him. We comprehensive field outcrops, wells, seismic reflection profiles with higher SNRs and aeromagnetic data, recognized about 20 normal fault-controlled rifting depressions of the Cryogenian and Ediacaran, which scattered throughout the basin, and developed on the Precambrian metamorphic and crystalline basement. The structural framework is clearly different from that of the overlying Phanerozoic. The rifting depressions consist of mainly half grabens, symmetrical troughs and horst-grabens. From the northeast to southwest of the basin, they are divided into three rifting depression groups(RDG)with the WNW, ENE, and NW-trends that are mainly controlled by normal faults. From the Cryogenian to Ediacaran, most of the main inherited faults to active and eventually ceased at the end of the Ediacaran or Early Cambrian, while subsidence centers appeared and migrated eastward along the faults. They formed under the NNESSW oriented and NNW-SSE-oriented extensional paleo-stress fields(relative to the present) during the Neoproterozoic, and were accompanied by clockwise shearing. According to the analysis of the activities of syn-sedimentary faults, filling sediments, magmatic events, and coordination with aeromagnetic anomalies, the tectonic properties of the fault depressions are different and are primarily continental rifts or intra-continental fault-controlled basins. The formation of the rifting depression was associated with the initial opening of the South Altun-West Kunlun Ocean and the South Tianshan Ocean, which were located at the northern and southern margins of the Tarim Block, respectively, in response to the break-up of the Supercontinent Rodinia and the initial opening of the Proto-Tethys Ocean.Inthe RDG developedfluvial, shallow marine and carbonate platform facies, accompanied with multiple phases of magma activities and glaciations during the Cryogenian and Ediacaran. The structural architectures of interfaces between the Neoproterozoic and Cambrian are mainly angular and parallel unconformities in the RDG. Over the parallel unconformities in the RDGs are beneficial for the organic-rich and/or phosphorites of the Yuertus Formation of the Lower Cambrian. The main fault belts of RDGs also controlled the small platform margin and slope break belt of in the Cambrian. The Neoproterozoic and the Lower Cambrian petroleum systems of the basin might be controlled by the RDGs in the initiation of the Tarimcraton.

Impact of Tropical Indian Ocean Temperature on the Ozone Layer in East Asia

Based on the reanalysis data of monthly mean sea surface temperature (SST) from British Hadley Center and ozone mass mixing ratio from National Aeronautics and Space Administration (NASA) during 1980-2015, two indexes IOBI and IODI of the main modes characterizing SST changes in the tropical Indian Ocean——Indian Ocean Basin (IOB) and Indian Ocean Dipole (IOD) were calculated firstly, and then the correlation of SST anomaly (SSTA) in the tropical Indian Ocean and ozone mass mixing ratio in the stratosphere over East Asia from 1980 to 2015 was analyzed. Besides, the impact of SST changes in the tropical Indian Ocean on the distribution of ozone layer in East Asia was discussed. The results show that SST changes in the tropical Indian Ocean had significant effects on stratospheric ozone distribution in East Asia, and it was consistent with the temporal changes of IOB and IOD. IOBI and IODI had a certain correlation with stratospheric ozone changes in East Asia, with a particularly significant correlation in the lower stratosphere (70 hPa) and middle stratosphere (40 hPa) especially during spring and autumn.

柴达木盆地周缘沉积锰矿带:一个极具资源潜力的锰矿集中区

近年来在阿尔金、祁连山和东昆仑地区的沉积型锰矿找矿工作取得了突破性进展。从空间分布特征看,这些锰矿均沿柴达木盆地周缘展布。前人曾针对单个矿床地质特征进行过研究,但对于柴达木盆地周缘的锰矿为什么主要形成于中—新元古代至早古生代、锰矿与柴达木地块及周缘造山带演化之间的关系等尚缺少深入的研究与总结。本文从东昆仑、阿尔金、祁连山等环柴达木盆地周缘造山带的角度,分析了沉积锰矿床地质特征和产出规律,重塑了原特提斯洋在青藏东北部的演化过程,为深入理解原特提斯构造演化与沉积锰矿成矿作用的关系提供证据。

南海中央海盆海底初始扩张时间的重新认定

由于磁异常条带识别的不确定性而使其具有多解性,因此对于应用磁异常条带对比得出的南海中央海盆海底初始扩张时间一直存在较大的争议。随着南海勘探活动的不断深入和资料的大量积累,有必要对这一重要问题给予重新认定。最新研究发现:南海中央海盆初始扩张区域的南、北边缘发育晚始新世-早渐新世(T7-Tog)沉积层序,说明洋壳基底之上的最早沉积层年代要老于原来认识的32-33Ma。在南海,持续时间长、活动强烈、形成近东-西向构造体系的变革运动发生时间为40Ma左右。南海陆缘不整合面对比证实,将T8界面(37.2-40Ma)作为南海初始扩张的破裂不整合面更为准确。由此得出结论,南海中央海盆海底初始扩张时间应为39-40Ma左右。

重力流与海底地貌动态相互作用下深水沉积体系发育演化——以大西洋赤道段菩提瓜尔盆地为例

海底地貌对重力流沉积具有重要控制作用并同时受到重力流沉积过程影响。针对重力流与海底地貌动态相互作用下深水沉积体系发育演化研究不足的问题,以大西洋赤道段菩提瓜尔盆地的局部沉积记录为解剖对象,基于三维地震资料,采用RGB三色融合技术,阐明了深水沉积体系发育演化特征,揭示了重力流与海底地貌的动态相互作用。研究区初始地貌中的主要地貌低点和次要地貌低点控制了早期深水水道和朵叶体的发育:(1)随着主要地貌低点斜坡坡度向远物源一端明显变缓,重力流的速度和能量逐渐减小,向下侵蚀能力变弱、侧向拓宽能力增强,水道剖面形态沿流向依次呈现V型、深U型及碟型;(2)因为水道限制性逐渐减弱,末端非限制性区域发育朵叶体沉积,朵页体上覆于水道充填沉积且向近物源一端生长,最终溢出到研究区西北角的次要地貌低点。水道和朵叶体沉积致使主要地貌低点远物源一端的斜坡坡度进一步变缓,后期块体流被捕获时,其沿流向携带沉积物的能力更容易降低,导致块体搬运沉积复合体(MTCs)在主要地貌低点远物源一端广泛堆积。

西准噶尔南部晚石炭世中-酸性火山岩成因机制及其对准噶尔洋闭合时限的约束

西准噶尔地区广泛分布石炭纪岩浆岩类,了解它们的成因和形成机制可为揭示准噶尔洋盆晚古生代构造格局和发展演化以及约束古大洋闭合时限提供重要依据。本文报道了西准噶尔南部哈拉阿拉特山地区晚石炭世中酸性火山岩的岩石学、锆石U-Pb年代学以及地球化学特征。岩石学研究表明其岩性主要为安山岩、英安质安山岩、流纹英安斑岩和流纹岩。LA-ICP-MS锆石U-Pb定年结果表明哈拉阿拉特山地区中酸性火山岩年龄为308~305 Ma,为晚石炭世中晚期。中酸性火山岩均相对富集轻稀土和大离子亲石元素,亏损Nb、Ta等高场强元素,富钠贫钾,属于低钾拉斑中钾钙碱性系列岛弧火山岩。其中安山岩和英安质安山岩具有较高SiO_(2)(56.15%~66.13%)、Al_(2)O_(3)(16.03%~17.94%)、Na_(2)O(3.44%~5.59%)、Sr((364~576)×10^(-6))含量和Na_(2)O/K_(2)O(3.20~6.40)、Sr/Y(33.5~55.6)比值,贫MgO(1.59%~2.68%)、Y((10.0~16.0)×10^(-6))和Yb((1.08~1.83)×10^(-6))的特征,并且具有Eu正异常(δEu=1.09~1.22),属于典型的埃达克岩,是经俯冲的洋壳板片在石榴角闪岩相发生部分熔融而成,且熔融产生的埃达克质熔体在上升过程中未与上覆地幔橄榄岩发生明显交代作用;流纹岩和流纹英安斑岩具有高的SiO_(2)(69.59%~75.03%)和全碱(w(Na_(2)O+K_(2)O)=7.81%~8.89%)、极低的TFe 2O 3(0.94%~1.57%)和MgO(0.12%~0.97%)含量以及弱负Eu异常(δEu=0.63~1.00)等特征,为准铝质I型流纹岩,是下地壳镁铁质岩石部分熔融的产物,很可能有少量幔源岩浆混入。综合本文数据并结合研究区大量前人已发表的岩浆岩类研究成果,认为西准噶尔南部地区在晚石炭世中晚期仍处于岛弧弧后盆地演化体系,准噶尔洋的闭合时限可能至少推迟至早二叠世早期之后。

鄂尔多斯盆地及邻区中—晚二叠世构造-沉积环境与原型盆地演化

根据钻井、测井、野外露头及地球化学资料,参考盆地周缘构造环境、盆地构造沉降特征及沉积相展布,恢复了鄂尔多斯盆地中—晚二叠世不同时期构造-沉积环境,探讨了盆地性质及演化过程。研究结果表明:①中—晚二叠世鄂尔多斯盆地南缘和北缘经历了洋盆俯冲消减过程,以强烈的挤压构造环境为特征,上二叠统石千峰组沉积期盆地北缘古亚洲洋闭合进入陆陆碰撞阶段,盆地内构造沉降速度缓慢。②中—晚二叠世鄂尔多斯盆地为大型的克拉通内坳陷盆地,中二叠统石盒子组沉积期基准面呈下降趋势,盆地主体延续山西组沉积期南北高、中部低的古地理格局,南华北地区地势相对更低;周缘隆起区快速抬升且范围逐渐扩大,为坳陷盆地内提供物源,盆地内发育冲积扇、冲积平原、三角洲和浅湖相,向南发育残存潮坪—潟湖,呈南北向展布;晚二叠世基准面趋于稳定,湖相范围扩大,主要发育于盆地南部,潮坪—潟湖环境向南缩小。③研究区油气成藏受控于沉积环境,中二叠世发育的陆相三角洲沉积体系有利于形成储集层和盖层,且和下部煤系地层组成中二叠统良好的生-储-盖组合;上二叠统为氧化干旱的古气候,沉积水体较浅,形成的泥岩厚度小,生烃潜力有限,无法形成大规模气藏。

特提斯洋与古亚洲洋协同演化控制下的塔里木台盆区油气富集效应

显生宙特提斯洋和古亚洲洋2大构造域演化历史对塔里木盆地产生了巨大的影响,其效应包括原型盆地的形成与沉积充填过程及油气成藏与调整改造等。原特提斯洋和古亚洲洋分别经历了扩张、俯冲-消减和关闭-碰撞造山过程。特提斯域经历了原特提斯、古特提斯和新特提斯3个阶段,具有此消彼长的关系。古亚洲洋在新元古代—古生代多陆-岛-洋的格架下经历了复杂的伸展—聚敛过程。受特提斯洋(昆仑-阿尔金分支洋)和古亚洲洋(南天山洋分支)协同演化控制,塔里木盆地经历了新元古代—早古生代和晚古生代—新生代2个从伸展—聚敛的巨型盆地旋回,与海平面升降和气候旋回匹配,形成了优质烃源岩、多类型规模性储层和盖层,构成了油气形成的优越物质基础。特提斯洋和古亚洲洋多圈层协同演化控制的油气富集效应体现在:①多类型盆地原型与后期构造改造决定了塔里木台盆区不同部位油气成藏与富集的差异性;②北部坳陷广泛分布的优质烃源岩,是塔北—顺托—塔中地区大型油气富集区形成的基础;③多期构造运动伴随的构造破裂与古岩溶作用造就了断控缝洞型和岩溶缝洞型2类各具特点且规模发育的储集体;④区内构造与地温场差异演化决定了油气聚集区内油气相态与次生改造的规律性变化。台盆区大型古隆起和不整合面、走滑断裂带、高能相带及其叠加区是油气有利目标区。