Provenance analysis of Eocene–Oligocene turbidite deposits in Pindos Foreland Basin, fold and thrust belt of SW Greece: constraints from framework petrography and bulk-rock geochemistry

The provenance of Eocene–Oligocene turbidites from the Pindos Foreland Basin, SW Greece, has been constrained using petrographical and geochemical techniques. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic, and plutonic igneous rocks deposited in a recycled orogenic environment and in magmatic arc province. The relative proportions of the detrital components indicate that the Late Eocene–Early Oligocene sandstones of West Peloponnesus are quartz-rich and were primarily derived from granitic and metamorphic basement rocks typically of a tectonically active area. Major, trace, and rare earth element (REE) concentrations in both sandstones and mudstones complement the petrographical data indicating an active continental margin/continental island arc signature. All the samples are light REE, enriched relative to heavy REE (HREE), with flat HREE pattern and positive Eu anomalies, suggesting that the processes of intra-crustal differentiation (involving plagioclase fractionation) were not of great importance. The results derived from the multi-element diagrams also suggest an active margin character and a mafic/ultramafic source rock composition.     

北祁连东段景泰地区下古生界两套砂岩微量元素和稀土元素特征及其构造意义

早奥陶世和早志留世是北祁连加里东造山带构造演化和盆地转变的关键时期。在造山带东段景泰地区,下奥陶统阴沟组和下志留统肮脏沟组两套砂岩的微量元素和稀土元素特征显示,阴沟组杂砂岩样品（Cj1和Cj3）具有最小的Eu/Eu*及最大的Th/Sc和REE,肮脏沟组杂砂岩具有较小的Eu/Eu*和较大的Th/Sc及REE;阴沟组岩屑砂岩样品（Cj13、Cj15和Cj18）具有最大的Eu/Eu*及最小的Th/Sc、REE和La/Yb。多个物源、构造背景判别图解和多元素蛛网图分析表明,阴沟组杂砂岩样品具大陆边缘的构造背景,主要物源为大陆上地壳再旋回沉积物和长英质岩石;岩屑砂岩样品为岛弧构造背景,以中基性安山质岩石为主要物源,可能受陆源物质的微弱影响。肮脏沟组杂砂岩构造背景复杂,表现出大陆岛弧、活动陆缘和被动陆缘三种环境共存的特点,受中基性火山弧物质、长英质岩石和再旋回沉积岩的混合物源的影响。两套砂岩的元素特征表明二者可能具有相似的源区。阴沟组杂砂岩源区可能为阿拉善地块南缘海原群变沉积岩或其他相似的陆源再旋回沉积物,砂岩碎屑以来自初始火山弧物质为主,以石灰沟岛弧型中基性火山岩作为其源岩最合适。阴沟组形成于初始弧后盆地环境,是岛弧活动的直接记录。肮脏沟组可能的源岩为阿拉善地块南缘海原群变沉积岩和中高等成熟度的石灰沟岛弧型火山岩及海原群岛弧型变火山岩,沉积于弧后前陆盆地,对构造环境的反映存在滞后性。     

Provenance and tectonic setting of Late Carboniferous clastic rocks in West Junggar,Xinjiang, China: A case from the Hala-alat Mountains

The Late Carboniferous palaeo-tectonic setting of the West Junggar region is comprised of arcs alternating with basins. Geochemical analysis of the sedimentary rocks associated with these arc-related basins was conducted to better constrain the provenance and tectonic setting.Major and trace element geochemistry data of Late Carboniferous mudstones and sandstones in the Hala-alat Mountains suggest that these sedimentary rocks and their source areas are characterized by the following four features: (1) sediments experienced a simple recycling process; (2) a low degree weathering conditions in the source areas; (3) compositional immature of the sedimentary rocks; (4) dominated by intermediate to felsic provenance, with a few intermediate to mafic sediments. Integrated with the palaeo-flow data and previous authors’ works, a fore-arc basin model is proposed for the tectonic setting of the sedimentary rocks. The Sawur arc is the primary provenance and supplies the major intermediate to felsic detrital fragments. The Bozchekul-Chingiz arc and Kexia oceanic island arc are the other two secondary sources.     

西秦岭造山带徽成盆地早白垩世地层物源综合分析

徽成盆地是西秦岭造山带内一个具有代表性的盆地,保留较完整的地层记录.早白垩世田家坝组、周家湾组和鸡山组为一套砂砾岩沉积组合序列.本文通过对早白垩世砂岩的古水流恢复、砾石成分与含量、重矿物和地球化学分析,对沉积岩物源区特征和原型盆地进行探讨.古水流恢复和砾石成分统计表明,沉积物主要是近源堆积,主要来自于盆地南缘和北部.重矿物研究结果表明,早白垩世砂岩母岩以岩浆岩为主,并有少量变质岩/沉积岩.地球化学分析表明,早白垩世砂岩为成熟度较低的硬砂岩和长石/岩屑砂屑岩.稀土元素标准化配分曲线呈现轻稀土富集、重稀土平坦和弱Eu负异常特征.砂岩物源区组成判别图研究表明,早白垩世砂岩的物源区主要出露长英质火山岩.砂岩源区构造环境判别图解及特征指数分析表明,早白垩世砂岩源区主要形成于大陆岛弧和活动大陆边缘.结合区域资料和前人研究,表明早白垩世徽成地区发育走滑拉分盆地.     

Detrital mode, mineralogy and geochemistry of the Sidi Aïch Formation (Early Cretaceous) in central and southwestern Tunisia: Implications for provenance, tectonic setting and paleoenvironment

The chemical and mineralogical composition of the Sidi Aïch Formation sandstones in central and southwestern Tunisia has been investigated in order to infer the provenance and tectonic setting, as well as to appraise the influence of weathering. The sixteen studied samples are mainly composed of quartz, feldspar, kaolinite and/or illite. Sidi Aïch sandstones are mainly arkosic, potassic feldspar-rich and immature. Much of the feldspar was transformed to kaolinite. Concerning the relation between sandstone detrital composition and their depositional setting, the Sidi Aïch Formation sandstone in the major studied localities, probably accumulated in relatively proximal small basins within the continental interior. However, for the Khanguet El Ouara study site, sandstones may have been deposited in a foreland basin which received recycled sediments from an adjacent orogenic belt.The source area may have included quartzose sedimentary rocks. The dominance of quartz and enrichment in immobile elements suggest that the depositional basins were associated with a passive margin. The petrography and geochemistry reflect a stable continental margin and sediments were derived from granitic and pegmatitic sources located in the southern parts of the Gafsa basin. High values for the chemical index of alteration (CIA) indicate that recycling processes might have been important. Particularly high CIA values in the Garet Hadid locality indicate more intense chemical alteration, either due to weathering processes or tectonic control.     

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     

Geochemical characteristics and depositional environment of the Middle Permian mudstones from central Qiangtang Basin,northern Tibet

Geochemical characteristics of the Middle Permian mudstones from the Longge Formation in the Jiaomuri area, central uplift zone of Qiangtang Basin have been analysed to constrain their provenance, tectonic setting, depositional redox condition and palaeoclimate. Based on the geochemical parameters like CIA, PIA, ICV values and Th/U, K/Rb ratios indicate that the source rocks were affected by low degree weathering conditions. The U/Th, V/Cr, Ni/Co, V/Sc ratios and U_au, C‐values of samples suggest that the mudstones were formed in an oxic environment, with arid palaeoclimate. Bulk‐rock geochemistry analysis indicates that they are mainly arkose and subarkose, derived from dominantly andesitic rocks, probably a mixing of felsic and mafic provenance. The CIA, PIA and ICV values of these samples suggest that the Longge mudstones are compositionally immature and related to moderate weathering. The tectonic discrimination diagrams, as well as critical trace and REE characteristic parameters imply an oceanic arc or continental arc setting for the depositional basin of mudstones from the Longge Formation, probably back‐arc basin. This study supports an occurrence of archipelagic oceanic basins in the Jiaomuri area in the Middle Permian, which provides evidence for the research of the Longmu Co–Shuanghu–Lancangjiang Suture. Copyright © 2015 John Wiley & Sons, Ltd.     

松辽盆地钱家店地区姚家组赋矿砂岩的组成、地球化学特征及其构造背景

松辽盆地钱家店地区姚家组砂岩矿物、地球化学成分与源区岩石性质和沉积构造环境密切相关。岩相学观察和矿物化学分析表明,所研究的岩石主要碎屑矿物由石英、岩屑和长石组成,含少量的黄铁矿、炭屑和重矿物等矿物。地球化学特征上,这些岩石普遍具有高SiO2含量(68.4%~79.61%)、相对高的K2O/Na2O比值(1.83~2.03)和较低的Fe2O3T+MgO含量(1.48%~4.22%),稀土元素标准化配分曲线呈现轻稀土富集,重稀土平坦和弱Eu、Ce负异常特征。较低的CIA(57~63)和PIA(60~71)指数、A-CN-K以及AK-C-N分布模式还说明源区经历了相对较弱的风化作用。Zr/Sc和Th/Sc比值共同表明姚家组的碎屑组成不具备沉积再旋回的特征,说明其为近源沉积,具有较差的分选性。砂岩物源区组成判别图研究表明,姚家组砂岩的物源区主要出露长英质岩浆岩。砂岩形成构造环境判别图解及特征指数分析表明,姚家组主要形成于被动大陆边缘沉积环境。     

右江盆地中三叠统浊积岩系的物源和沉积构造背景分析

右江沉积盆地在大地构造位置上被称为右江印支褶皱带。浊积岩碎屑组分特征、重矿物组分特征和古流向等特征显示赋矿的中三叠统浊积岩系的主要物源区为盆地周围的“越北古陆”、“江南古陆”和东边地区包括钦防海西褶皱带在内的“云开古陆”。浊积岩的稀土元素特征、微量元素特征和常量元素特征一致显示其沉积构造背景介于大陆岛弧和活动大陆边缘之间的过渡构造环境。     

四川攀枝花昔格达组及其下伏河流砾石的地球化学特征以及对物源的制约

位于扬子地块西缘的攀枝花地区昔格达组湖相沉积及其下伏河流相砾石比较发育。湖相沉积具有较高的SiO2含量和Al2O3/SiO2比值,显示其载体沉积物具有较高成熟度,表明经历了长距离的搬运。主元素、稀土(REE)和微量元素分析结果揭示昔格达组湖相沉积物源形成于典型的大陆岛弧构造背景,主要来自松潘-甘孜造山带义敦岛弧花岗岩区。Eu/La?Yb/La判别图与Zr/Y比值进一步证实昔格达组湖相沉积分别来自于金沙江上游及雅砻江上游,说明昔格达古湖形成时金沙江上游已被袭夺。昔格达组下伏河流相砾石REE、微量元素分析结果显示其形成于被动大陆边缘构造背景,说明其是由雅砻江经扬子板块边缘花岗岩区携载而来。昔格达组湖相沉积与其下伏河流相砾石的不同物源特征表明伴随着昔格达古湖的形成,金沙江河流经历了演化史上的巨变。     

西昆仑塔什库尔干下-中侏罗统龙山组沉积构造背景分析

新疆塔什库尔干地区下-中侏罗统龙山组,位于最新填绘的唐盖河-新迭村构造混杂岩带（康西瓦构造带）的南侧,总体为一套青灰色-灰色碳酸盐岩-碎屑岩沉积,主要以泥灰岩和杂砂岩为主,源区岩石没有经过充分的搬运、分选,成熟度比较低。稀土元素特征表现为轻稀土元素富集、重稀土元素相对平坦和Eu亏损明显的特征,与典型上地壳非常相似;而微量元素质量分数也接近于大陆上地壳值;说明下-中侏罗统龙山组物源来自上地壳。沉积环境综合分析表明,龙山组沉积环境为浅海陆棚-近滨-前滨环境,表现出进积特征,总体为一个海退序列,反映了寒冷干燥的气候条件下,海平面下降、残留海盆收缩的沉积构造环境。从物源区构造背景来看,龙山组以活动大陆边缘为主,兼具大陆岛弧性质。结合区域地质构造背景,龙山组为羌塘地块和昆仑地块拼合之后形成的残留洋边缘沉积,其主要物源来源于其北侧的康西瓦构造带。     

若尔盖盆地中、晚三叠世沉积岩微量元素地球化学特征及其构造背景

位于松潘-甘孜带东北部的若尔盖盆地是中、晚三叠世时期松潘-甘孜构造带北部重要的沉积区。对若尔盖地区的红参一井内中三叠世中期和晚三叠世中期的37个杂砂岩样品进行了ICP-MS微量元素分析,其结果显示这些砂岩样品具有Cs、Rb、Th等元素富集,Sr、Nb和Ta亏损,稀土元素总量较高,且负Eu异常和轻重稀土分异明显等壳源物质的特征;而微量不活动元素的含量及比值特征以及构造环境判别图解的判别结果表明:若尔盖盆地中三叠世中期到晚三叠世中期的沉积构造环境为大陆岛弧,沉积物源受到大陆岛弧的强烈影响。通过对比杂砂岩稀土元素组成在上层和下层样品之间的变化,若尔盖盆地内中三叠世中期到晚三叠世中期及晚期沉积物源区的构造背景和性质发生了明显的改变,而这一变化很可能是盆地东侧成熟陆壳在晚三叠世后期被抬升和剥蚀,其大量碎屑物质被带到盆地的结果。     

Geochemistry of Silurian–Carboniferous sedimentary rocks of the Ulaanbaatar terrane,Hangay–Hentey belt,central Mongolia: Provenance,paleoweathering, tectonic setting,and relationship with the neighbouring Tsetserleg terrane

The Hangay–Hentey belt is situated in the central Northern Mongolia, and forms part of the Central Asian Orogenic Belt (CAOB). It is internally subdivided into seven terranes, the largest of which are the neighbouring Ulaanbaatar and Tsetserleg terranes. These coeval terranes are mainly composed of Silurian–Devonian accretionary complexes and Carboniferous turbidites. Proposals for their depositional setting range from passive margin through to island arc. A suite of 19 Ulaanbaatar terrane sandstones and mudrocks (Gorkhi and Altanovoo Formations) were collected with the aim of constraining their provenance, source weathering, and depositional setting based on whole-rock major and trace element data, and for comparison with the neighbouring Tsetserleg terrane. New REE analyses were also made of 35 samples from the Ulaanbaatar and Tsetserleg terranes. Geochemically the Ulaanbaatar sandstones are classed as wackes, and most of the mudstones as shales. Geochemical parameters suggest an immature source, similar to that of the Tsetserleg terrane. Geochemical contrasts between sandstones and mudrocks in the Ulaanbaatar sediments are small, and trends on element – Al₂O₃ variation diagrams are weak. Comparison with average upper continental crust (UCC), major element discriminant scores, and immobile element ratios (Th/Sc, Zr/Sc, Ce/Sc, Ti/Zr) indicate a uniform average source composition between dacite and rhyolite. Maximum Chemical Index of Alteration value in the Ulaanbaatar terrane is ∼65 after correction for K-metasomatism, indicating minimal weathering in a tectonically active source, similar to that of the Tsetserleg terrane. REE data in both terranes show moderate LREE enrichment and flat HREE segments, with negative Eu anomalies somewhat less than those in UCC and PAAS. Chondrite-normalized patterns are very similar to that for average Paleozoic felsic volcanic rock, supporting the relatively felsic source indicated by immobile trace element ratios. Tectonic setting discriminants (K₂O/Na₂O–SiO₂/Al₂O₃, La–Th–Sc, Th–Sc–Zr) indicate an evolved continental island arc (CIA; A2) environment for both terranes, similar to several other CAOB suites of similar age. This common arc source was situated within the Mongol-Okhotsk Ocean during Silurian–Lower Carboniferous time. The present-day Aleutian arc is a possible modern analogue of the depositional setting.     

Detrital composition of Ordovician sandstones from the Rügen boreholes: implications for the evolution of the Tornquist Ocean

The Lower Palaeozoic sequences of the Rügen boreholes are composed of pelitic-clastic sediments which range in age from the Cambro-Ordovician boundary to the Late Ordovician. Provenance studies have been carried out on Cambro-Ordovician sandstones from the Loissin borehole and on Middle-Upper Ordovician greywackes of the Rugen 5 borehole.The Loissin sandstones were deposited as turbidites and debris flows in an unstable sedimentary basin. They form immature arkoses and subarkoses with high matrix contents. Their debris derived from a polycyclic, sedimentary cratonic provenance and from a monocyclic magmatic provenance. This is reflected in the heavy mineral spectrum, which is dominated by an anhedral, coloured zircon fraction and a euhedral, transparent zircon fraction.The Middle-Upper Ordovician Rügen greywackes derived from proximal, high energy turbidites which were transported into a deep marine basin. They form homogeneous lithic arkoses and arkosic litharenites. Their debris derived from a composite provenance with an ultramafic-mafic, ophiolitic source, an acidic magmatic source and a heterogeneous sedimentary cratonic source.Although the Loissin sandstones probably originated in an intracratonic, rift-related sedimentary basin, the debris of the Rugen greywackes is regarded as derived from a heterogeneous active continental margin. Results and interpretations of the provenance study are discussed in the light of proposed Lower Palaeozoic palaeogeographic reconstructions.     

北大巴山地区斑鸠关组砂岩地球化学特征对物源和构造环境的限定

北大巴山是南秦岭造山带的重要组成部分,保留较完整的地层记录。长期以来,斑鸠关组被认为形成于相对稳定的构造环境。本文通过对斑鸠关组砂岩的沉积序列和地球化学分析,详细分析其物源区和形成构造环境。沉积学特征表明,斑鸠关组砂岩主要为一套深水沉积的细砂岩、粉砂岩和泥岩组合序列,形成于海底扇。砂岩中交错层理恢复的古流向表明,其物源主要来自于北侧。地球化学分析表明,斑鸠关组砂岩SiO₂为61.54%～84.35%,主要为成熟度较低的岩屑砂屑岩。稀土元素标准化配分曲线呈现轻稀土富集、重稀土平坦和Eu负异常的特征。砂岩的风化蚀变指数为51～67,Th/U比值为3.36～7.02,表明砂岩物源区经历了较弱的风化作用。Zr/Sc和Th/Sc比值指示斑鸠关组砂岩没有经历沉积再旋回,为近源沉积。砂岩物源区组成判别图表明,斑鸠关组物源主要为长英质岩石。砂岩源区构造环境判别图以及特征指数表明,斑鸠关组源区形成于大陆岛弧和被动大陆边缘环境。综合区域资料,表明斑鸠关组形成于大陆岛弧相关环境,非大陆裂谷。     

库车坳陷第三系泥岩地球化学特征及其对构造背景和物源属性的指示

利用碎屑岩地球化学特征判断沉积盆地的构造背景和物源属性是盆地分析的重要手段，也是对利用粗碎屑沉积岩的组分统计判断盆地源区背景的有益补充和验证。对库车坳陷第三系36件泥岩样品的地球化学特征分析表明，主量元素中CaO的含量很高，对其他主量元素以及微量和稀土元素有稀释作用，一些可靠的物源分析指标主要指示了非碳酸盐沉积物的源区性质；REE分布模式与上地壳相似，轻稀土元素富集，Eu负异常，微量元素比值显示源岩以长英质岩石为主。通过K2O／Na20-SiO2以及La-Th-Sc和Th-Sc-Zr／10判别图分析，认为源区的构造背景具有类似于岛弧的特征。这一结果与前人所做的砂岩组分的研究结果存在差异，说明板内造山带与其前陆盆地之间在沉积与构造耦合上具有特殊性。     

黑龙江省东部早古生代晨明组物源区特征及其构造背景

为揭示黑龙江省东部早古生代晨明组沉积物源区特征及其沉积构造背景,对晨明组进行了地球化学特征研究。结果表明：晨明组岩石样品化学蚀变指数（I_CA）值和斜长石蚀变指数（I_PA）值较低、成分变异指数（I_CV）值中等偏高,指示晨明组沉积物来源于不成熟的物质源区,并经历了较弱的化学风化作用和活动构造背景下的初次循环;LREE富集、HREE稳定和明显的负Eu异常,指示沉积物源区物质具有明显的上地壳特征且沉积物源岩为长英质火成岩;主量、微量和稀土元素特征共同指示晨明组形成于活动大陆边缘环境或大陆岛弧环境。结合前人研究成果,判定晨明组沉积物来源于经历了弱-中等程度化学风化作用的早古生代花岗质岩,沉积构造背景可能为靠近大陆岛弧的活动大陆边缘环境。     

Detrital zircon ages in Palaeozoic and Mesozoic basement assemblages of the Peninsular Ranges batholith,Baja California,Mexico: constraints for depositional ages and provenance

The origin and continuity of Phanerozoic lithostratigraphic terranes in southern and Baja California remain an unsolved issue in Cordilleran tectonics. We present data from eight detrital zircon samples collected across the southern extent of the Peninsular Ranges that help constrain the provenance of detritus and the depositional ages of these basement units. Detrital zircon signatures from units in the eastern Peninsular Ranges correlate with Palaeozoic passive margin assemblages in the southwestern North American Cordillera. Units in the central belt, which consists of Triassic–Jurassic metasedimentary turbidite assemblages that probably deformed in an accretionary prism setting, and Cretaceous metasedimentary and metavolcanic units that represent the remnants of a continental margin arc, were derived from both proximal and more distal sources. The westernmost units, which are locally structurally interleaved with the Triassic through Cretaceous units of the central belt, are Cretaceous deposits that represent a series of collapsed basin complexes located within and flanking the Cretaceous Alisitos volcanic island arc. Cretaceous intra-arc units show little influx of cratonal material until approximately 110 Ma, whereas coeval sediments on the northern and eastern flanks of the Alisitos arc contain abundant cratonal detritus. Intra-arc strata younger than approximately 110 Ma contain large amounts of Proterozoic and older detrital zircons. These data suggest that basins associated with the Alisitos arc were either too distant or somehow shielded from North American detritus before 110 Ma. In the case of the former, increased influx of continental detritus after 110 Ma would support a tectonic model in which the arc was separated from North America by an ocean basin and, as the arc approached the continent, associated depositional centres were close enough to receive input from continental sources.     

西昆仑造山带中带提热艾力组沉积环境 及物源区构造背景

西昆仑造山带中带上石炭统提热艾力组为一套浅变质碎屑岩沉积,四周被三叠纪岩浆岩所包围,研究其沉积环境及物源特征对揭示该区构造背景具有重要的意义。通过野外详细的剖面测制、沉积相标志的观察,结合室内岩矿鉴定和地球化学等综合分析,揭示该套碎屑岩具典型的鲍马序列结构特征,岩性成分成熟度低,主要为一套近物源的斜坡重力流沉积,其物源区较为复杂,主要为切割岩浆弧、过渡岩浆弧和再旋回造山带,源区构造环境为大陆岛弧及活动大陆边缘,表现出活动大陆边缘弧后盆地的沉积特点。     

西昆仑造山带中带提热艾力组沉积环境及物源区构造背景

西昆仑造山带中带上石炭统提热艾力组为一套浅变质碎屑岩沉积,四周被三叠纪岩浆岩所包围,研究其沉积环境及物源特征对揭示该区构造背景具有重要的意义。通过野外详细的剖面测制、沉积相标志的观察,结合室内岩矿鉴定和地球化学等综合分析,揭示该套碎屑岩具典型的鲍马序列结构特征,岩性成分成熟度低,主要为一套近物源的斜坡重力流沉积,其物源区较为复杂,主要为切割岩浆弧、过渡岩浆弧和再旋回造山带,源区构造环境为大陆岛弧及活动大陆边缘,表现出活动大陆边缘弧后盆地的沉积特点。