Modal analysis and geochemistry of two sandstones of the Bhander Group (Late Neoproterozoic) in parts of the Central Indian Vindhyan basin and their bearing on the provenance and tectonics

The Neoproterozoic Bhander Group in the Son Valley, central India conformably overlying the Rewa Group, is the uppermost subdivision of the Vindhyan Supergroup dominantly composed of arenites, carbonates and shales. In Maihar-Nagod area, a thick pile of unmetamorphosed clastic sedimentary rocks of Bhander Group is exposed, which provides a unique opportunity to study Neoproterozoic basin development through provenance and tectonic interpretations. The provenance discrimination and tectonic setting interpretations are based on modal analysis and whole rock geochemistry. The average framework composition of the detrital sediments composed of quartz and sedimentary lithic fragments are classified as quartz arenite to sublitharenite. The sandstone geochemically reflects high SiO₂, moderate Al₂O₃ and low CaO and Na₂O type arenite. The high concentration of HFSE such as Zr, Hf, and Th/Sc, Th/U ratios in these sandstones indicate a mixed provenance. The chondrite normalized REE pattern shows moderate to strong negative Eu anomaly which suggests that major part of the sediments were derived from the granitic source area. The sandstone tectonic discrimination diagrams and various geochemical plots suggest that the provenance of the lower and upper Bhander sandstone formations was continental interior to recycled orogen.     

鄂尔多斯盆地白垩系洛河组风成砂岩地球化学与物源区特征:以靖边县龙洲乡露头为例

通过镜下观察,岩石常量元素、稀土微量元素含量测定等手段对鄂尔多斯盆地白垩系洛河组风成砂岩进行实验分析,研究其地球化学和物源区特征。确定洛河组风成砂岩地球化学岩石类型为长石砂岩和亚长石砂岩,沉积物的成熟度较高;物源区为被动大陆边缘构造背景占主导地位的再旋回造山带,并含有大陆岛弧的特性;沉积物母岩为变质岩、沉积岩,并含少量的酸性、中基性岩浆岩;物源区气候寒冷干旱,为氧化环境,化学风化程度低。     

Geochemistry and Provenance of Maastrichtian Clastic Rocks in the Dikmendede Formation of Orhaniye in Kazan-Ankara-Turkey Region

An integrated petrographic and geochemical study of the sandstones of the Maastrichtian-aged in the Orhaniye (Kazan-Ankara-Turkey) was carried out to obtain more information on their provenance, sedimentological history and tectonic setting. Depending on their matrix and mineralogical content, the Maastrichtian sandstones are identified as lithic arenite/wacke. The Dikmendede sandstones derived from types of provenances, the recycled orogen and recycled transitional. The chemical characteristics of the Dikmendede sandstones, i.e., fairly uniform compositions, high Th/U ratios (>3.0), negative Eu anomalies (Eu/Eu* 0.72–0.99) and Th/Sc ratios (mostly less than 1.0), favor the OUC (old upper continental crust) provenance for the Dikmendede sandstones. The SiO2/Al2O3, Th/Sc (mostly <1.0) and La/Sc (<4.0) ratios are; however, slightly lower than typical OUC, and these ratios may suggest a minor contribution of young arc-derived material. The rare earth element (REE) pattern, and La/Sc versus Th/Co plot suggests that these sediments were mainly derived from felsic source rocks. The Dikmendede sandstones have high Cr (123–294 ppm) and Ni (52–212 ppm) concentrations, Cr/Ni ratio of 1.93, and a medium correlation coefficient between Cr and Ni and corresponding medium to high correlation of both (Cr and Ni, respectively) elements with Co. These relationships indicate a significant contribution of detritus from ophiolitic rocks. As rare earth element data are available for the Dikmendede sandstones, the Eu/Eu* is compared with LaN/YbN. Samples plot in the area of overlapping between continental collision, strike-slip and continental arc basins. The predominantly felsic composition of the Dikmendede sandstones is supported by the REE plots, which show enriched light REE, negative Eu anomaly and flat or uniform heavy REE. The Dikmendede sandstones have compositions similar to those of the average upper continental crust and post-Archean Australian shales. This feature indicates that the sediments were derived mainly from the upper continental crust. The Dikmendede sandstones have chemical index of alteration (CIA) values of 28–49, with an average of 40 indicating a low degree of chemical weathering in the source area. The compositional immaturity of the analyzed sandstone samples is typical of subduction-related environments, and their SiO2/Al2O3 and K2O/Na2O ratios and Co, Sc, Th and Zr contents reflect their oceanic and continental-arc settings. The Dikmendede sandstones were developed as flysch deposits derived from mixed provenance in a collision belt.     

Petrography and geochemistry of Silurian Niur sandstones,Derenjal Mountains,East Central Iran: implications for tectonic setting,provenance and weathering

Petrographical and geochemical studies of Silurian Niur sandstones, Derenjal Mountains, Central Iran, were carried out to infer their provenance and tectonic setting. Modal analysis data of 37 medium sand size and well-sorted samples revealed that most quartz is composed of monocrystalline grains with straight to slightly undulos extinction and about 3 % polycrystalline quartz has inclusions, such as rutile needles. The sandstones are classified as quartzarenite, sublitharenite, and subarkose types based on framework composition and geochemistry. Petrographic studies reveal that these sandstones contain quartz, feldspars, and fragments of sedimentary rocks. The detrital modes of these sandstones indicate that they were derived from recycled orogen and stable cratonic source. Major and trace element contents of them are generally depleted (except SiO₂) relative to upper continental crust which is mainly due to the presence of quartz and absence of Al-bearing minerals. Modal composition (e.g., quartz, feldspar, and lithic fragments) and discrimination diagrams based on major elements, trace elements (Ti, La, Th, Sc, and Zr), and also such ratios as La/Sc, Th/Sc, La/Co, and Th/Co, in sandstones suggest a felsic igneous source rock and quartzose polycyclic sedimentary provenance in a passive continental margin setting. Furthermore, high Zr/Sc values in these sandstones are considered as a sign of recycling. We indicated paleo-weathering conditions by modal compositions, the CIA index and Al₂O₃?+?K₂O?+?Na₂O% vs. SiO₂% bivariate for these sandstones. Based on these results, although recycling is important to increase the maturity of the Niur sandstones, humid climate conditions in the source area have played a decisive role.     

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.     

准噶尔盆地南缘侏罗系碎屑成分特征及其对构造属性、盆山格局的指示意义

砂岩碎屑成分分析是进行沉积物源岩石类型、构造属性和盆山演化分析的重要途径。准噶尔盆地南缘侏罗系物源构造属性以“再旋回造山带”、“弧造山带”和部分“岩浆弧”物源为特征,物源岩石类型主要为中酸性岩浆岩、变质岩和沉积岩,岩石成分、重矿物含量及其组合显示东、西剖面在物源上存在一定差异。天山内部侏罗系物源构造属性以“再旋回造山带”、“混合造山带”为主,物源岩石类型主要为中酸性岩浆岩和变质岩,但各剖面的岩石成分、重矿物组合特征及相对含量差异较大。综合天山内部与准噶尔盆地南缘野外剖面沉积特征、岩屑成分及钻井岩心分析表明,天山地区早、中侏罗世盆山格局以盆地沉积范围大、天山正地形较小为特征,不存在地理分割明显的天山山脉,侏罗纪盆地南缘至少存在三个物源体系(西准噶尔山、克拉麦里山和(古)天山);晚侏罗世一早白垩世早期,岩石成分成熟度偏低,砾岩等粗碎屑沉积明显增多,同时不稳定重矿物及其组合稍有增加可能与晚侏罗世天山构造格局分异、构造活动相对活跃有关,天山山脉明显隆升并造就天山南北沉积环境的巨大差异。     

天山南缘石炭系-三叠系碎屑岩成分及其对物源区大地构造属性的指示

本文通过对天山南缘石炭系-三叠系碎屑岩岩石学特征和地球化学特征的分析,揭示了研究区石炭系-三叠系碎屑岩的物质组分特征及其物源区的大地构造背景.碎屑岩的岩石学、地球化学分析表明,天山南缘石炭系、三叠系砂岩成分成熟度和结构成熟度均不高,杂基含量较高,从石炭系至三叠系砂岩不稳定组分依次增加.石炭系、二叠系具有相似的稀土元素含量特征,三叠系稀土元素含量明显低于石炭系和二叠系,石炭系-三叠系轻、重稀土元素分馏程度依次减弱,La/Th、La/Y 比值依次增大,Th/U比值减小,来自再旋回的物质依次增多.综合碎屑组分、常量元素、稀土元素及微量元素特征的判别,天山南缘石炭系物源区构造背景为既有指示大陆岛孤、活动大陆边缘的证据,也有指示为被动大陆边缘,二叠系物源区示为大陆岛弧,三叠系物源区示为大陆岛弧和含有古老沉积岩的陆块.对比石炭系、二叠系及三叠系物源区的大地构造属性,石炭系物源区示有多种属性,而二叠系、三叠系则相对较为单一,这可能与中天山-伊犁地块和塔里木陆块的碰撞有关.     

兰坪中新生代盆地沉积岩源区构造背景和物源属性研究--砂岩地球化学证据

沉积盆地中砂岩的地球化学成分主要受物源区控制。因此，通过分析砂岩的化学成分可以揭示盆地沉积岩的源区构造背景和物源属性。对兰坪盆地中新生界砂岩的常量成分、稀土和微量元素进行的分析，揭示盆地沉积岩的源区构造背景属被动大陆边缘和大陆岛弧，结合岩相古地理资料认为在中生代以前，盆地东侧可能主要处于被动大陆边缘环境。而西侧则可能以大陆岛弧环境为主，这与区域地质资料相吻合。沉积物源岩的原始物质应来自上地壳，以长英质岩石为主，并有少量安山质岩石和古老沉积物的混入，故兰坪中新生代盆地属典型的大陆型盆地。从而为正确认识古特提斯洋的演化和盆山转换过程提供了强有力的地球化学证据。     

鄂尔多斯盆地晚古生代沉积岩源区构造背景及物源分析

鄂尔多斯盆地周缘物源均来自上地壳,以长英质岩石为主,主要为太古宇、元古宇的各类变火山-沉积岩组成的古老变质岩系,同时具有一定量的花岗岩和碱性玄武岩的混合,但物源成分及南北源区构造背景有所差异。在常量元素及稀土元素组成上,盆地南北物源区的沉积岩在地区及层位之间存在差异,且该变化符合大洋岛弧→大陆岛弧→活动大陆边缘→被动大陆边缘常量元素、稀土元素以及负Eu异常的变化趋势。常量元素变化分析表明盆地北部物源主要来自板块俯冲碰撞地带,与被动大陆边缘环境和活动大陆边缘环境相关,少数为与活动大陆边缘相关的岛弧构造环境有关,到晚古生代中晚期才逐渐与被动大陆边缘环境和活动大陆边缘环境相关。稀土元素对比分析表明,盆地北部物源与太古宙、元古宙的花岗片麻岩、闪长片麻岩、二长花岗岩、变余岩屑砂岩及千枚岩具有亲源性;而盆地南部早—中二叠世长期受被动大陆边缘物源影响,具有高SiO2,低Na2O的特征,这与太古宙—元古宙的太华群、秦岭群、宽坪群等岩系的高SiO2含量,K2O/Na2O>1的特征一致,到晚古生代后期,逐渐与活动大陆边缘物源相关。北秦岭晚古生代山间盆地具有快速混杂堆积的沉积特点,属于盆地外缘,并与鄂尔多斯盆地呈连续过渡的状况,物源上具有继承关系;盆地晚古生代沉积岩中Gd含量及(Gd/Yb)N比值具有随时间迁移的特征,分析表明北部物源区在太原期处于构造快速活动期,而南部物源从山西期才开始进入快速活动期,这与区域构造演化背景一致,即北部物源区抬升要早于南部。     

Geochemistry of Lower Jurassic sandstones of Shemshak Formation,Kerman basin,Central Iran: Provenance,source weathering and tectonic setting

Lower Jurassic sandstones of Shemshak Formation of Kerman basin, central Iran were analyzed for major and select trace elements to infer their provenance, palaeoweathering of source rocks and tectonic setting. Average modal framework components (Qt: F: L= 67.25: 2.41: 30.48) and chemical composition of the sandstones classify them as litharenites. The sandstones are quartz-rich (～ 67% quartz; 75.34 wt.% SiO₂) and derived from a recycled orogen composed of quartzose sedimentary rocks. Average CIA, PIA and CIW values (69%, 76% and 80%, respectively) indicate moderate to intense chemical weathering of the source material. The inferred index of weathering/alteration is the sum total of intensities of weathering witnessed by the lithocomponents during atleast two cycles of sedimentation involving (1) chemical weathering of the source rocks («ultimate» granodiorite source and «proximal» quartzose sedimentary source), (2) chemical weathering during fluvial transport of the detritus, (3) chemical weathering of the detritus in depocenters, and (4) chemical weathering during diagenesis. Sandstones exhibit moderate maturity and were deposited under humid climatic conditions. Plots of the chemical analyses data on tectonic setting discrimination diagrams indicate active continental margin setting, which is in agreement with the tectonic evolutionary history of the Central Iran during Jurassic period.     

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.     

酒西盆地中新生代碎屑组分特征及指示意义

通过岩石碎屑成分分析,研究酒西盆地砂砾岩储集层沉积碎屑成分特征对物源属性、盆-山格局演化及油气成藏特征的指示意义。研究表明,酒西盆地下白垩统下沟组砂岩成分成熟度低,物源构造属性以再旋回造山带和部分岩浆弧为特征,物源岩石类型主要为中酸性岩浆岩和变质岩(沉积岩碎屑极少),岩石成分及其组合显示盆地东、西部的物源差异明显;古近系白杨河组在岩石成分、岩屑组成上与下白垩统下沟组砂岩有较大不同,显示物源属性的明显改变。物源属性的改变在一定程度上反映构造格局分异、盆-山格局的演变历程,控制了酒西盆地内油气富集和晚期成藏特征。碎屑成分特征在一定程度上决定了储集层的储集空间类型及裂缝发育规律,值得进一步深入研究。     

云南思茅盆地江城上白垩统勐野井组稀土微量元素特征及地质意义

沉积盆地中碎屑岩的地球化学成分主要受物源区控制,因此,通过分析碎屑岩的化学成分可以揭示盆地沉积岩的源区构造背景和物源属性。思茅盆地上白垩统勐野井组（K2me）细碎屑岩的稀土元素组成分析结果表明,研究区沉积物具有轻稀土元素富集,较平坦的重稀土元素分布模式,以及中等程度 Eu 负异常的总体特征。根据样品的（Hf-La/Th、La/Sc-Co/Th和REE-La/Yb）图解,特征性微量元素比值（La/Sc、Sc/Th、Cr/Th 和 Co/Th）,并结合岩矿薄片分析,认为勐野井组细碎屑岩具有典型的上陆壳特征,源区母岩以长英质岩石为主。微量元素 Cr/Co 结合岩相古地理的分析显示勐野井组细碎屑沉积物应属于近源沉积。通过与不同构造背景下杂砂岩的稀土元素特征对比及主元素（K2O/Na2O-SiO2/Al2O3和SiO2-K2O/Na2O）判别图解,勐野井组细碎屑岩源区构造背景应属被动大陆边缘环境,这与思茅盆地所处的三江造山带构造背景相符。     

苏北东台坳陷古新统阜宁组三段微量、稀土元素地球化学特征及其地质意义

沉积岩的微量、稀土元素对沉积环境的水介质变化有着较高的敏感度,对于研究古环境、沉积物源性质和构造背景方面具有重要的意义。前人对于东台坳陷元素地球化学方面的研究相对薄弱,利用元素地球化学资料解释古环境和源区性质方面的研究尚属空白。本文以苏北东台坳陷古新统阜宁组三段20件泥岩样品为研究对象,对其进行微量、稀土元素测定,并分析其地球化学特征及所揭示的地质意义。结果表明:(1)Sr含量、Sr/Cu、Rb/Sr、La_n/Yb_n比值指示干热气候;Li、Sr、Ni、Ga微量元素含量和Sr/Ba比值均指示淡水—半咸水的水体环境,整体以淡水环境为主,偶有咸水注入盆地,局部为半咸水环境;而V/(V+Ni)、V/Cr、Ni/Co、U/Th、δCe指示氧化—弱还原的水体环境。(2)Co/Th—La/Sc、La/Th—Hf判别图解和稀土元素配分模式,表明阜宁组三段沉积岩应来自于上地壳的长英质物质。(3)La—Th—Sc、Th—Co—Zr/10和Th—Sc—Zr/10构造背景判别图解反映了大陆岛弧与活动大陆边缘的构造背景,且与Bhatia不同构造背景杂砂岩的微量、稀土元素特征值的对比分析结果一致。     

苏北盆地高邮凹陷始新统戴南组一段稀土元素特征及其物源指示意义

稀土元素(REE)的物源对比表明,苏北盆地高邮凹陷戴南组一段沉积岩的物源以其西侧张八岭隆起的元古宙浅变质岩基底为主,并与大别和苏鲁造山带的浅变质岩基底存在亲缘关系,推断研究区的母岩类型为高钾I型花岗片麻岩。而张八岭隆起的新元古代细碧—石英角斑岩和绿片岩、中生代火成岩、大别山南部大范围的榴辉岩以及宁镇山脉的中生代中酸性侵入岩对研究区的物源影响很小。在高邮凹陷内部的物源方向分析中,轻重稀土元素分馏值[(La/Yb)N]与矿物成熟度指数(MMI)形成很好的吻合,(La/Yb)N值结合稀土元素总量(∑REE)及铕异常值(δEu)可对研究区内物源方向的精确判别具有指示意义。戴南组一段沉积时期,高邮凹陷的物源主要来自4个方向:西北部柘垛低凸起方向、东部吴堡低凸起方向、南部通扬隆起方向和西南部菱塘桥低凸起方向。高邮凹陷戴南组一段的沉积相类型与REE特征的相关性分析显示,重稀土元素分馏值[(Gd/Yb)N]与沉积相间存在较为规律的变化,表现在近岸水下扇相、扇三角洲相和三角洲相随其碎屑岩的成熟度升高,(Gd/Yb)N平均值呈逐渐升高的趋势,该趋势同样表现在相同沉积相的不同沉积亚相之间,说明(Gd/Yb)N平均值可较好地反映沉积相特征。     

Depositional environment and tectono-provenance of Upper Kaimur Group sandstones,Son Valley,Central India

The Mesoproterozoic Upper Kaimur Group consists of Bijaigarh Shale, Scarp Sandstone, and Dhandraul Sandstone. Based on the lithofacies data set, two major facies associations were identified, namely—tidal sand flat/sand bar facies association (TSFA) and tidally influenced fluvial channel facies/tidal channel facies association (TIFCFA). The Dhandraul Sandstone has been interpreted as a product of TIFCFA and the underlying Scarp Sandstone in TSFA which endorses a tidal dominated estuarine setting. Detrital modes of the Dhandraul and Scarp Sandstones fall in the quartz arenite to sub-litharenite types. Petrographical data suggest that the deposition of the Upper Kaimur Group sandstones took place in humid climate and was derived from mixed provenances. The sandstone composition suggests detritus from igneous rocks, metamorphic rocks, and recycled sedimentary rocks. The sandstone tectonic discrimination diagrams suggest that the provenances of the Upper Kaimur Group sandstones were continental block, recycled orogen, rifted continental margin to quartzose recycled tectonic regimes. It is envisaged that the Paleo- and Mesoproterozoic granite, granodiorite, gneiss, and metasedimentary rocks of Mahakoshal Group and Chotanagpur granite–gneiss present in the western and northwestern direction are the possible source rocks for the Upper Kaimur Group in the Son Valley.     

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。     

Geochemical fingerprints and pebbles zircon geochronology: Implications for the provenance and tectonic setting of Lower Cretaceous sediments in the Zhucheng Basin (Jiaodong peninsula,North China)

This paper conducts a petrogeochemical analysis of the Lower Cretaceous Laiyang Group’s sandstones, compares the results with the Neoproterozoic and Mesozoic intrusive rocks in the southern Sulu Orogen (also called the Jiaonan Orogen), and performs an LA-ICP-MS zircon geochronology analysis of the granitic gneisses in the conglomerates of the Laiyang Group and the intrusive rocks in the Jiaonan Orogen. The results show that the major element proportions of the Longwangzhuang Formation (LWZ Fm) and Qugezhuang Formation (QGZ Fm) of the Laiyang Group in the Zhucheng Basin are similar. The values of various indices for the LWZ Fm are similar to the average sandstone content of active continental margins, whereas, the values for the QGZ Fm are similar to those of continental island arcs. The comparison shows that the REE characteristics of the LWZ Fm and QGZ Fm of Laiyang Group are similar to those of the Neoproterozoic granitic gneisses in the Jiaonan Orogen but obviously different from those of the Early Cretaceous intrusive rocks. A tectonic setting discrimination diagram reveals that the provenance of the Laiyang Group includes features of active continental margins and continental island arcs. A number of indicators, e.g., the sandstone type, the Chemical Index of Alteration, the Chemical Index of Weathering, the Plagioclase Index of Alteration and the Index of Chemical Constituent Variation, indicated that the sandstones did not undergo intense weathering and were deposited near the source area. The zircon ages of the granitic gneiss material in the conglomerates at the base of the Laiyang Group are 790 ± 8.4 Ma, close to the ages of the Neoproterozoic granitic gneiss in the Jiaonan Orogen (739–819 Ma), and very different from the ages of the Early Cretaceous intrusive rocks. Combining with paleocurrent directions, geochemical character, the Neoproterozoic granitic gneisses in the Jiaonan Orogen may represent the primary provenance of the Laiyang Group in the Zhucheng Basin. During the depositional period of the Laiyang Group, the source rocks did not experience intense weathering, which indicated the Jiaonan Orogen experienced rapid uplift during this time, and coincided with the high exhumed rate of 2.0 km Ma ^?1 from before ca. 128 to 123 Ma in Jiaonan Orogen. The rapid subsidence during the formation of the Laiyang Group in the Zhucheng Basin and the rapid uplift of the Jiaonan Orogen are the result of a single regional extensional event associated with the lithospheric thinning and destruction of North China and peripheral cratons.     

Geochemistry of Tertiary sandstones from southwest Sarawak,Malaysia: implications for provenance and tectonic setting

Tertiary sandstones collected from southwest Sarawak, Malaysia, were analyzed to decipher their provenance, weathering, and tectonic setting. The studied sandstones have a sublitharenite composition and are dominantly composed quartz with little mica and feldspar, and a small amount of volcanic fragments. These sandstones were generally derived from quartz-rich recycled orogenic sources. They have relatively high SiO₂ content with low Na₂O, CaO, MnO, and MgO contents. Values of Chemical Index of Alteration (CIA) of these rock samples vary from 71 to 93, with an average of 81, implying intense chemical alteration during weathering. A felsic igneous source is suggested by a low concentration of TiO₂ compared to CIA, enrichment of Light Rare Earth Elements, depletion of Heavy Rare Earth Elements, and negative Eu anomalies. A felsic origin is further supported by a Eu/Eu* range of 0.65–0.85 and high Th/Sc, La/Sc, La/Co, and Th/Co ratios. This work presents the first reported geochemical data of Tertiary sandstones of the Sarawak Basin. These data led us to conclude that the sandstones were dislodged from recycled orogenic sources and deposited in a slowly subsiding rifted basin in a passive continental tectonic setting.     

Geochemistry of Carboniferous Sandstones (Sardar Formation), East‐Central Iran: Implication for Provenance and Tectonic Setting

Geochemical analysis of sandstones from the Sardar Formation (from two stratigraphic successions) in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation (e.g., K2O/Na2O vs. SiO2) indicate deposition in a stable passive continental margin (PM). Chemical index of alteration (CIA) for these rocks (> 65%) suggests a moderate to relatively high degree of weathering in the source area.