Cenozoic Sedimentary Sequence in the Kumkal Basin, Xinjiang and New Evidence for the Late Quaternary Uplift of the Qinghai-Tibetan Plateau

1. IntroductionThe Qinghai-Tibetan Plateau is an importantregion for the study of the global change andstructural evolution history). The in-depth knowledgeon its uplift process is the ke}' to understand theformation and development of temporary ph}'sicalenvironment of China or even East Asia. Therefore.a large quantity of researchers have given muchmore attention on this field (Burbank et al.. l982;Fang Xiaornin et al.. 1995f Ruddoman. ]997f AnZhisheng et al.. 1998). The macroscopic e\'o…     

Sedimentary Conditions of Evaporites in the Late Jurassic Xiali Formation, Qiangtang Basin: Evidence from Geochemistry Records

The Qiangtang Basin (QB), located in the central Tibetan Plateau, is a Jurassic marine basin and one of the most important prospective salt resource belts in China. In recent decades, many outcrops of gypsiferous?bed have been found in the Jurassic marine strata in the basin. Salt springs with abnormally high sodium (Na+) contents had been identified in the Late Jurassic Xiali Formation (Fm.) in the basin in the last years. However, to date, no potash or halite deposits have been identified in the QB. Gypsum outcrops and salt springs are very important?signs in the investigation of halite and potash deposits. Therefore, the Xiali Fm. is?a potentially valuable layer to evaluate for the possible presence of halite and potash deposits in the basin. However,?few studies?have explored the formation?conditions of evaporites in the unit. Here, we present detailed geochemical records from the Yanshiping section related to the study of the formation?conditions of evaporites in the Xiali Fm. of the QB. Climate proxies based on the obviously increased anion concentrations of SO42? and Cl? and the significant correlation?coefficients of Ca2+-SO42? (R = 0.985) and Na+-Cl? (R = 0.8974) reveal that the upper member of the Xiali Fm. (the upper Xiali Fm.) formed under an arid climate and evolved into the sulfate phase or early chloride phase. Provenance proxies based on the obviously increased K+ and Na+ ion concentrations and the significant correlation?coefficient of Na+-Cl? (R = 0.8974) suggest that the upper Xiali Fm. featured optimal provenance conditions for the possible formation of halite deposits. The regression and the semi-closed tidal?flat environment in the upper Xiali Fm. were favorable for the formation of potash and halite deposits. The low Mg2+ /Ca2+ values (mean value = 1.82) and significant Na+-Cl? correlation?coefficient (R = 0.8974) also suggest that the upper Xiali Fm. is the layer most likely to contain potential halite deposits. In addition, the macroscopic correlations of tectonism, provenance, paleoclimate, saliferous strata and sedimentary?environment between the QB and the adjoining Amu Darya Basin in Central Asia reveal that the two basins shared similar geologic settings that were favorable for the formation of evaporites during the Late Jurassic. Therefore, the upper Xiali Fm. is a valuable layer to explore for halite deposit and may be potentially valuable in the future exploration for potash deposits in the QB.     

Geochemical Constraints of Sediments on the Provenance, Depositional Environment and Tectonic Setting of the Songliao Prototype Basin

The geochemistry of sediments is primarily controlled by their provenances, and different tectonic settings have distinctive provenance characteristics and sedimentary processes. So, it is possible to discriminate provenances, depositional environments and tectonic settings in the development of a sedimentary basin with the geochemistry of the clastic rocks. The analytical results of the present paper demonstrate that sediments in the Songliao prototype basin are enriched in silica (SiO2=66.48-80.51 %), and their ΣREE are 30-130 dmes of that of chondrite with remarkable Eu anomalies. In discriminating diagrams of Eu/Eu vs eeeeeREE and (La/Yb)N vs ΣREE, most samples locate above the line Eu/ Eu=l, on the right of the line Eu/Eu/ΣREE=1 and under the line La/Yb)N/eeeeeREE=1/8, which indicates that the depositional environment of sediments in the basin was oxidizing. In addition, variations of MgO, TiO2, A12O3, FeO+Fe2O3, Na2O and CaO vs SiO2 reflect a tendency of increasing mineral maturity of sediments     

Plio‐Pleistocene tectonics and eustasy in the Gippsland Basin,southeast Australia: Evidence from magnetic imagery and marine geological data

The Pliocene and Pleistocene sediments of the Gippsland shelf are dominated by mixed carbonates and siliciclastics. From a detailed stratigraphic study that combines conventional marine geology techniques with magnetic imagery, the Late Neogene tectonic and eustatic history can be interpreted and correlated to the onshore section. Stratigraphic analyses of eight oil and gasfield foundation bores drilled to 150 m below the seabed revealed three principal facies types: (i) Facies A is fine‐grained limestone and limey marl deeper than 50 m below the seabed, of Late Pliocene age (nannofossil zones CN11–12); (ii) Facies B is a fine‐coarse pebble quartz‐carbonate sand that occurs 10–50 m below the seabed in the inner shelf, grading down into Facies A in wells in the outer shelf, and is of Early‐Middle Pleistocene age (nannofossil subzones CN13a-14b: ca 1.95–0.26 Ma); and (iii) discontinuous horizons of Facies C composed of carbonate‐poor carbonaceous and micaceous fine quartz sand occurring 10–50 m below the seabed. The sparse benthic foraminifers in Facies C are inner shelf or Gippsland (euryhaline) Lakes forms. Holocene sands dominate the upper 1.5–2.5 m of the Gippsland shelf and disconformably overlie cemented limestones with aragonite dissolution, indicating previous exposure to meteoric water. Nannofossil dating of the limestones indicates ages within subzone CN14b (dated between ca 0.26 and 0.47 Ma). Airborne magnetic imaging across the Gippsland shelf and onshore provides details of buried magnetic palaeoriver channels and barrier systems. The river systems trend south‐southeast from the Snowy, Tambo, Mitchell, Avon, Macalister and Latrobe Rivers across the shelf. Sparker seismic surveys show the magnetic palaeochannels as seismic ‘smudges’ 20–40 m below the seabed. They appear to correspond to Facies C lenses (i.e. are Early to Middle Pleistocene features). Magnetic palaeobarrier systems trending south‐southwest in the inner shelf and onshore beneath the Gippsland Lakes are orientated 15° different to the modern Ninety Mile Beach barrier trend. Offshore, they correlate stratigraphically to progradation packages of Facies B. Analysis of bore data in the adjacent onshore Gippsland Lakes suggests that a Pliocene barrier sequence 100–120 m below surface is overlain by fluvial sand‐gravel and lacustrine mud facies. The ferruginous sandstone beds resemble offshore Facies C, and are located where magnetic palaeoriver channel systems occur, implying Early to Middle Pleistocene ages. Presence of the estuarine bivalve Anadara trapezia in the upper lacustrine mud facies suggests that the Gippsland Lakes/Ninety Mile Beach‐type barriers developed over the past 0.2 million years. Further inland, magnetic river channels that cut across present‐day uplifted structures, such as the Baragwanath Anticline, suggest that onshore Gippsland uplift continued into the Middle Pleistocene.     

Tectonic Setting and Nature of the Provenance of Sedimentary Rocks in Lanping Mesozoic- Cenozoic Basin： Evidence from Geochemistry of Sandstones

The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements, rare-earth dements and trace elements of the Mesozoic-Cenozoic sandstones in the Lanping Basin are studied in this paper, revealing that the tectonic settings of the provenance for Mesozoic-Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography, it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic, whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust, and are composed mainly of felsic rocks, mixed with some andesitic rocks and old sediment components. Therefore, the Lanping Mesozoic-Cenozoic Basin is a typical continental-type basin. This provides strong geochemical evidence for the evolution of the paleo-Tethys and theb asin-range transition.     

Lithology,Biostratigraphy, and Geochronology of the Late Pleistocene–Holocene Sediments on the Coast of Onega Bay of the White Sea

Doklady Earth Sciences - This paper reports on the lithological, micropaleontological, and chronometric data (radiocarbon dating) for one of the areas of the White Sea coast. The sedimentary...     

Dating and Fluid Geochemistry of the Sarkobu Gold Deposit in Altay, Xinjiang, China

The dating of fluid inclusions of quartz yields an Ar-Ar isochrone age of 320.4±6 Ma. Three types of fluid inclusions have been identified with the homogenization temperature ranging from 157℃ to 362℃. The homogenization temperature consists of two groups. The first group varies from 157℃ to 166℃, and the second from 232℃ to 362℃. Their chemical composition is dominated by Na+-Ca2+-Mg2+ and Cl-. The relative concentration of ions is characteristic by Na+>Ca2+>K+>Mg2+ and C1->SO42-> F-. The δD and δ18O values indicate that the ore-forming fluid originates from mixing of multi-source water. The Sarkobu gold deposit has experienced two mineralization stages: gold was enriched during the volcanic-exhalative-sedimentary process in the early stage, while the gold deposit was finally formed under compression-shearing during the orogenic period.     

^40Ar-^39 Ar Dating of Quartz from Ore in the Baiyangping Cu-Co Polymetallic Ore-Concentrated Area, Lanping Basin, Yunnan

⁴⁰Ar−³⁹Ar fast neutron activation age spectrum of quartz in ore collected from the Baiyangping Cu−Co polymetallic ore-concentrated area, Lanping Basin, is saddle-shaped. The plateau age, minimum appearance age and isochron age shown on the spectra are 56.53±0.43 Ma, 55.52±1.78 Ma and 55.90±0.29 Ma respectively. The age data are consistent with each other within 1σ uncertainties. Because the given initial⁴⁰Ar/³⁶Ar value of 294.7±1.14 is very close to Nier's value (295.5±5), both plateau and isochron ages may be considered as the forming time of quartz. So the age of 55.90–56.53 Ma represents the forming age of ore deposits. It is obvious that the ore deposits were formed during the Early Himalayan period. This research project was granted by the State Basic Research, Development and Planning Program (G1999043208) and the Foundation Projects of Yunnan Provincial Education Department (No. 0142104).     

Tectonic shortening and crustal thickening in subduction zones: Evidence from Middle–Late Jurassic magmatism in Southern Qiangtang,China

We report new zircon U–Pb geochronologic and Hf-isotopic data, and whole-rock major and trace element data, for the Labuco granitoids of the southern margin of the Southern Qiangtang terrane (SQ), Tibet. Five intermediate–felsic samples yielded zircon U–Pb ages of 169–156 Ma, making the Labuco granitoids contemporaneous with Middle–Late Jurassic magmatism in the SQ. The granitoids exhibit a range of zircon εHf(t) values from − 7.3 to − 0.6. The samples from Labuco can be divided into low-Sr/Y granitoids (LSG) and high-Sr/Y granitoids (HSG). The LSG are normal calc-alkaline I-type granitoids, characterized by varying major and trace element contents indicative of partial melting of ancient mafic lower crust. The HSG are characterized by high Sr/Y ratios (64–75), (La/Yb)_N (chondrite-normalized) ratios of 57–76, and (Gd/Yb)_N ratios of 6.6–8.9. These signatures indicate that the HSG were derived by partial melting of garnet-bearing thickened lower crust. The across-arc variation in magma geochemistry in the SQ was caused by tectonic shortening and crustal thickening, which occurred as a result of the northward subduction of the Bangong–Nujiang Ocean lithosphere during the Middle–Late Jurassic. These results have important implications for our understanding of tectonic shortening, crustal thickening, and the geometry of modern and ancient subduction zones.     

敦煌盆地早更新世沉积物粒度分析、36Cl定年及其构造隆升意义

青藏高原早更新世末期的快速隆升对全球气候变化、中国西部盆山地貌形成与荒漠化的发展有着重大影响。高原东北缘敦煌盆地早更新世河湖相沉积物粒度分析和红色泥岩³⁶Cl 断代法定年结果表明：早更新世晚期（1.164 ~1.087 Ma B.P.）,青藏高原北部党金山快速隆升,砾石层和粗砂层发育,沉积速率加快;1.087~ 0.809 Ma B. P.,山脉隆升速度变缓,沉积速率降低;0.809 Ma B. P.以来,受山脉隆升的影响,敦煌盆地气候逐渐变得干旱,沙漠形成。区域分析表明,沉积速率所反映的中国中西部山脉隆升最新的年代存在差别,不同时期高原的隆升产生不同的气候效应。因此,构造隆升和气候变化的细节尚待进一步研究。     

藏南江孜盆地构造演化的石英ESR测年证据

江孜盆地是特提斯喜马拉雅构造带北部典型的中新生代沉积盆地。对该盆地东段构造剖面(哲古错-措美南)的石英脉进行ESR测年,获得的年龄分布区间为63.8～4.3Ma,对应于古新世早期-上新世早期。测年结果对于江孜盆地断裂活动的多期性及盆地新生代的构造演化具有重要约束意义,表明江孜盆地的构造演化可划分为盆地主体构造形成(古新世初期)、构造定型(始新世晚期—中新世晚期)和构造改造(上新世及之后)3个主要阶段。     

江南隆起带北缘新生代构造演化的石英ESR年代学研究

运用α石英热活化ESR定年法对江南隆起带北缘35件样品进行了研究。结果显示,江南隆起带北缘的石英脉ESR年龄范围在195.8~3.4 Ma之间,主要集中在喜山期(75~3.4 Ma)。结合其他地质证据,江南隆起带北缘新生代构造演化可以划分为伸展断陷期(75~61.5 Ma)和挤压隆升期(43.2~3.4 Ma)两个阶段。前者以发育正断层和断陷盆地为特征,后者以重力滑脱构造为特征。喜山期的构造作用对先存构造进行了强烈的改造,包括南华北、中下扬子和江南隆起带北缘的整个中国东部地区在喜山期都经历了显著的构造活动。ESR测年结果与江南隆起带已有地质事实相吻合,检验了ESR测年的可靠性。     

新疆伊犁盆地的构造特征与形成演化

伊犁盆地是在天山造山带所夹持的微地块上发展演化而成的山间叠合盆地,其现今垂向结构为自下而上由中、新元古代变质基底、石炭纪裂谷火山岩系变形基底和二叠纪以来的盆地沉积岩系组成的３ 层结构,南北向剖面形态总体为两侧造山带相对向盆地逆冲的对冲构造几何学样式,伊犁盆地内则呈现为二山三盆的复杂次级山 盆构造组合。伊犁盆地的形成演化与天山造山带,尤其与其南北两侧相邻的不同性质造山带密切相关。伊犁地块和盆地的形成演化可概括为４ 个大的构造阶段和４ 个成盆期。现今的伊犁盆地正是不同成盆期的原型盆地复合叠置的综合产物。石炭－ 二叠纪和侏罗纪是伊犁山 盆构造系统的主造山成盆期。     

新疆西天山伊犁地块晚古生代火山岩地质特征及构造意义

对新疆西天山伊犁盆地晚古生代火山岩时空分布和地质特征、岩石化学等进行系统总结,认为该盆地晚古生代火山岩主要由晚泥盆世至早二叠世的火山岩组成,其形成与南北天山洋盆演化有关.晚泥盆—早石炭世大哈拉军山组火山岩为天山南北洋盆大洋板块俯冲而成的钙碱性火山岩,晚石炭世伊什基里克组火山岩为挤压环境向拉张环境过渡的钙碱性火山岩和碱性火山岩,早二叠世乌郎组火山岩为后造山具裂谷特征的双峰式火山岩组合.     

临夏盆地晚更新世沉积物粘土矿物的特征及其古气候指示

利用X射线衍射、扫描电子分析方法,对临夏地区塔湾黄土沉积物的粘土矿物学特征及其古气候指示作用进行了深入研究。结果表明：晚更新世的黄土沉积物风成黄土或经过表生风化改造形成的古土壤,其粘土矿物组成主要为伊利石、绿泥石、伊/蒙混层粘土矿物、高岭石和少量的坡缕石,沉积物中高岭石、伊利石/蒙脱石、伊利石和绿泥石矿物组合,指示物源区经历了气候从湿润变为冷干的转变。沉积物中伊利石结晶度的测量结果显示,其（001）衍射峰的半高宽在0.23°~0.86°之间,不同岩性层中伊利石结晶度存在明显的差别,伊利石结晶度存在着两个明显的峰值区,这表明临夏地区晚更新世的气候变化经历了从湿润→冷干→湿润→冷干的两个周期性的演化,而且晚期与早期相比更加湿润同时又更为冷干。沉积物中既有自生成因的坡缕石,又有碎屑成因的坡缕石。沉积物中自生成因坡缕石和碎屑成因坡缕石均稳定存在的现象表明,本区晚更新世的古气候是以干旱为特征,年均降雨量在300 mm左右。     

鄂尔多斯盆地南缘晚奥陶世钾质斑脱岩——SHRIMP测年及其成因环境

鄂尔多斯盆地南缘上奥陶统金粟山组以深水碳酸盐岩沉积为特征,含多层桔黄色凝灰质粘土岩。矿物和化学成分分析表明,其主要由伊利石和伊蒙混层粘土矿物组成,含少量石英、长石和锆石等中酸性岩浆矿物,富K2O,属钾质斑脱岩;微量元素分析显示本区斑脱岩的源岩为中酸性岩浆成因,源于同碰撞火山弧构造环境。应用SHRIMP技术对其中的锆石进行了U-Pb测年,取得了(451.5±4.9)～(452.1±5.1)Ma、(457.5±5.1)Ma和(465.8±8.3)Ma 3组谐合年龄,前两者分别与欧美广布的Millbrig-Kinnekulle和Deicke斑脱岩同时,但15种化学组分的多元统计分析显示,金粟山组的斑脱岩与欧美同期著名的斑脱岩可能并不同源。形成本区斑脱岩的火山凝灰质可能源自沿商丹洋盆北缘展布的火山弧喷发,而鄂尔多斯盆地南缘晚奥陶世发生的强烈沉降和沉积转换可能与北秦岭弧后盆地的拉伸与扩张密切相关。     

伊犁地块北缘早古生代构造属性:来自温泉地区闪长岩的证据

温泉地区位于伊犁地块与哈萨克斯坦板块结合部位,广泛发育早古生代侵入岩,侵入岩带对探究伊犁地块北缘早古生代构造背景及洋陆演化具有重要意义。在野外地质填图和岩相学观察基础上,对温泉地区奥陶纪闪长岩开展了系统的锆石U-Pb年代学、Hf同位素和地球化学研究。年代学表明,石英闪长岩3个样品锆石U-Pb加权平均年龄分别为（467.7±5.4）、（457.1±3.9）和（455.4±5.0）Ma,表明其结晶时间从中奥陶世一直持续到晚奥陶世早期。地球化学成分显示,闪长岩SiO₂质量分数（50.19%~61.91%,平均56.57%）、TiO₂质量分数（0.84%~1.13%,平均1.01%）较低,MgO质量分数（2.36%~8.17%,平均4.60%）、CaO质量分数（3.94%~9.45%,平均6.50%）和全碱质量分数（3.74%~7.06%,平均5.41%）相对较高,并具有高的Na₂O/K₂O值（1.42~4.90,平均2.76）,以及低的A/CNK值（0.70~0.95,平均0.84）,为准铝质岩石。微量元素地球化学显示闪长岩富集大离子亲石元素（K、Rb等）,亏损高场强元素（Ta、Nb、Ti等）;球粒陨石标准化稀土元素分布模式表现为"左陡右缓"的变化趋势,Eu显示弱的负异常（δEu=0.67~1.12,平均值0.90）,重稀土元素质量分数较低,具有大陆边缘弧火成岩地球化学特征。Harker二元图解表明,岩浆演化过程中发生了分离结晶作用,存在于岩体中的地层捕虏体显示其经历了一定的地壳混染。两件石英闪长岩样品具有相近的Hf同位素组成：ε_Hf（t）值为3.9~7.0,两阶段模式年龄（T_DM2）为991~1 191 Ma（平均1 083 Ma）,远远大于锆石U-Pb年龄。以上特征表明亏损地幔在闪长岩源区占主导地位,并有早期大洋板片流体交代的富集岩石圈地幔组分的混入。综合地质资料和前人研究成果,推测区内闪长岩形成时的动力可能与准噶尔洋奥陶纪持续向南俯冲有关,洋盆最终于晚奥陶世-早志留世闭合。     

新疆伊犁盆地512矿床水文地球化学特征

在系统分析伊犁盆地 5 12砂岩型铀矿床成矿地质背景基础上 ,阐述了补给区、径流区和排泄区地下水水文地球化学特征 ,并由此得到矿区氧化带、矿化带地下水化学类型分别为SO4·HCO3-Na·Ca型和HCO3·SO4-Ca·Na型 ,其水化学成分演化过程与岩石中硫化物氧化和脱硫酸作用有关 ,水化学类型为铀矿化地段的确定提供了证据。     

北美五大湖区晚更新世劳伦泰德冰盖演化年代学综述及石英光释光测年的初步尝试

北美五大湖区的安大略湖北岸Don Valley Brickyard、Scarborough Bluffs、Bowmanville Bluffs剖面共同构成了北美东北部最长也是最厚的陆地第四纪沉积记录, 较完整地记录了晚更新世劳伦泰德冰盖(the Laurentide Ice Sheet)的演化. 晚更新世劳伦泰德冰盖演化的重建有赖于这些经典剖面中重要沉积地层单元的准确年代学控制. 传统的地层年代学主要是依靠少量¹⁴C年代, 将主要的混杂堆积单元(diamicton)解释为气候变冷环境下的冰川扩张, 并与指示全球冰量变化的深海氧同位素曲线一一比对建立起来的. 这样建立起来的年代学存在很大的不确定性. 20世纪80-90年代的少量热释光年代也不相吻合, 最近的13个长石红外释光定年则只集中于Bowmanville Bluffs的一个分层, 并未建立整个剖面的地层年代学, 使这些经典沉积剖面的年代学一直没有得到系统的建立. 应用石英光释光SAR-SGC法测试了Bowmanville Bluffs剖面Glaciofluvial Sand单元的2个冰水沉积样品, 年代结果分别为(41.6±3.8) ka、(48.1±4.4) ka, 分析表明这一年代结果偏老, 石英颗粒可能晒褪不完全. 由于大测片无法识别晒褪不完全的颗粒, 因此, 测试更多的剖面序列的光释光年代并尝试采用粗颗粒小测片或单颗粒技术解决样品颗粒晒褪不完全的问题将是必要的.