The Upper Miocene Injana (Upper Fars) Formation of Iraq: insights on provenance history

Petrographic, geochemical, and scanning electron microscope analyses of the sandstone and mudstone units of the Upper Miocene Injana Formation are presented. Furthermore, microprobe analysis for amphiboles, pyroxenes, garnet, and chromian spinels as common heavy mineral species present is done to support other results for better understanding of the provenance history of the Injana Formation. The sandstones of the Injana Formation consist of terrigenous carbonate lithic fragments as common type of sedimentary rock fragments in addition to chert, argillaceous, and rare sandstone fragments. They also include metamorphic and igneous lithic fragments, quartz, feldspars, and mica and generally, the sandstones are lithic arenites and immature. Scanning electron microscopic analysis for the heavy minerals shows that they have been affected by dissolution due to chemical etching and mechanical abrasion through several surface texture generated either in arid and semihumid environment or in diagenetic environment. Clay mineralogy of the mudstone units indicates the presence of illite, chlorite, kaolinite, palygorskite, and illite–smectite mixed layers. Bulk-rock and mineral phase geochemistry in addition to petrographic data suggest the derivation of the Injana Formation from a nearby sources with contribution from igneous, metamorphic, and sedimentary provenance mainly from the high lands in the northeastern parts of Iraq which comprise mainly the Zagros mountains and the older sedimentary formations.     

开鲁盆地钱家店凹陷含铀岩系姚家组沉积环境及其富铀意义

利用10多口钻孔岩心、电测曲线和分析化验资料,对钱家店凹陷含铀岩系姚家组沉积环境及古气候进行了分析.姚家组为一套以中细粒为主的砂质辫状河沉积产物.含矿层主岩为岩屑长石砂岩和长石岩屑砂岩,粒度概率累积曲线以悬浮总体含量较高为特征的两段式.一个完整的垂向序列由含砾砂岩或中细砂岩向上变细为粉砂岩和少量泥岩组成的正韵律.碎屑组分含量变化和重矿物分析表明,沉积物源主要来自盆地西北部古隆起的酸性岩浆岩和变质岩.泥岩元素分析、孢粉分析及泥岩颜色等指示,姚家组沉积期古气候主要为亚热带干旱气候,在这一大的气候背景下有过程度较弱的短暂潮湿化事件发生.干旱-半干旱气候为层间氧化带的形成提供了有利的气候条件,周边古隆起或更远山地的酸性火山岩、古老结晶岩和变质岩为该区提供了丰富的铀源,广泛发育、物性较好的辫状河道砂体为铀矿化提供了良好的储渗空间.     

柴北缘西段古近纪物源体系分析

沉积区物源分析对研究造山带构造演化、盆地沉积过程及划分油气区带等方面具有重要的意义。为了查明柴达木盆地北缘构造带古近纪物源方向,通过对古近系碎屑岩的碎屑组成、岩屑成分、重矿物组合特征和ZTR指数的研究,并结合前人的研究成果,初步确定古近纪柴北缘西段发育五大主力物源区:(1)牛东物源主要来自阿尔金山东段,重矿物组合以稳定且含量较高的电气石区别于邻区,碎屑组分中以石英和含量较高的长石为特征,岩屑中含有少量的碳酸盐岩岩屑;(2)冷北物源主要来自小赛什腾山方向,重矿物组合中榍石和赤铁矿的含量明显偏高,碎屑组分中以高岩屑为特征;(3)赛西物源主要来自赛什腾山西段,电气石和角闪石含量较高,碎屑组分较为均一,母岩以变质岩和火成岩为主,含少量碳酸盐岩岩屑;(4)赛东物源主要来自赛什腾山东段,其白钛矿含量明显高于邻区,碎屑组分以较高含量的石英和长石为主,岩屑类型主要为变质岩、火成岩和沉积岩岩屑;(5)九龙山物源主要来自九龙山和绿梁山地区,石榴石含量高且稳定,碎屑组分较为均一,母岩以变质岩和火成岩为主,含少量的非碳酸盐岩类沉积岩岩屑。     

北秦岭小寨变质沉积岩系的地质特征及其构造意义

原岩恢复、沉积建造及变形变质综合研究表明,北秦岭小寨变质沉积岩系属活动陆缘性质沉积建造,形成于二郎坪弧后盆地消减俯冲带的海沟盆地-海沟斜坡环境,是古俯冲带的重要证据之一,其变形序列反映了弧后盆地构造演化过程,并与构造混杂岩、俯冲型花岗岩及高压变质带一起构成相对完整的古俯冲带标志,为探讨秦岭古生代板块构造演化提供了重要信息。     

碎屑重矿物分析对库车坳陷白垩—第三纪物源变化的指示

碎屑沉积是山脉隆升和盆地沉积的直接记录，包括碎屑重矿物研究在内的碎屑沉积物的分析是开展盆山耦合研究的必要手段。对库车坳陷白垩系—第三系砂岩中重矿物含量特征进行了系统的研究，并应用电子探针技术分析碎屑石榴石和钛铁矿的化学组成，研究表明库车坳陷白垩—第三系源区主要由沉积岩、变质岩和酸性火山岩组成。白垩系砂岩中的石榴石来自西南天山蓝片岩和低级变质岩的比例较大，而第三系砂岩中的石榴石中富铁铝榴石组分，多来自高级变质岩。白垩系砂岩中的钛铁矿多来自变质岩，上第三系砂岩中来自火成岩的钛铁矿比例增加。由此可以认为南天山的大规模隆升和剥蚀发生在第三纪以来，由于它的隆升遮挡了南天山北缘古生代增生杂岩体对库车坳陷的物质贡献，并且随着剥蚀的加深，高级变质岩和火成岩的出露越来越多。     

Tectonic Setting of the Late Proterozoic Lavalleja Group (Dom Feliciano Belt), Uruguay

The Lavalleja Group exposed along the Dom Feliciano orogenic belt is located in the southeast of Uruguay. This group consists of volcano-sedimentary rocks, developed during the Neoproterozoic Brasiliano cycle. The geochemical signature of the igneous rocks of the Lavalleja Group, mainly metagabbros and basic and acidic metavolcanic rocks, indicates a back-arc basin tectonic setting. The metamorphic grade increases to the southeast, from very low grade, lower green-schist facies, in the Minas Formation, to a medium grade, amphibolite facies, in Fuente del Puma and Zanja del Tigre Formations. The metamorphic mineral assemblages correspond to a low-pressure regional metamorphism associated with a high thermal gradient. A compressive deformational event that probably corresponds to the closure of the Lavalleja basin during a continental collision, was recognized. The petrology, geochemistry, metamorphic grade, and tectonic setting are consistent with a back-arc basin setting for the Lavalleja Group.     

Geochemistry and petrology of Late Miocene-Pleistocene Dibdibba sandstone formation in south and central Iraq: implications for provenance and depositional setting

Major, trace, and some rare earth element compositions in clastic sediments of the Dibdibba Formation (Late Miocene-Pleistocene) in central and southern Iraq have been investigated to describe the sedimentary environment and provenance. These sediments are classified as subarkosic to arkosic with few sublithic arenite, lithic arenite, and gray wacke; they are mainly composed of quartz (Q) followed by feldspar (F) and rock fragments (L) with a petrologic composition of Q73-F21-L6. The Arabian Shield is a probable source of the studied sediments which are derived from multi-sources including igneous rocks (felsic to mafic) and metamorphic rocks and were transported by river currents towards the northeast. Eventually, the clastic sediments were deposited in a fluviatile environment covering a wide area in Saudi Arabia, Kuwait, Qatar, and Iraq during the Late Miocene-Pleistocene. They were developed on a passive continental margin under a semi-humid climate alternating with drought periods. The grain size analysis indicates that Basra in the south of Iraq is close to the source, but Karbala and Najaf in central Iraq are farthest from the source.     

Provenance of the late Paleocene sandstones of the Jaisalmer Basin,Western India

Provenance of the late Paleocene sandstone of the Jaisalmer basin has been determined by petrographic and heavy minerals analysis supported by paleocurrent study. Petrography of the quartzose-arenite sandstone reveals an abundance of sub-angular to sub-rounded monocrystalline non-undulatory quartz and some amount of feldspar and rock fragments. The rock fragments are dominated by argillites (slate, phyllite) and limestone. The heavy minerals suite of these sandstones comprises of angular to sub-angular grains of magnetite, zircon, tourmaline, kyanite and staurolite. The paleocurrent analysis indicates bipolar paleocurrent pattern with the dominance of NW flow suggesting that the provenance was in the SE direction of the depositional basin. Q-F-L and Qm-F-Lt diagrams suggest for a provenance at the margin of the craton interior and transitional continental. It is envisaged that the basic igneous rocks of the Deccan basalt, low- to medium-grade metamorphic rocks of the Aravalli belt and Jurassic limestones present in the vicinity are the source rocks for the late Paleocene sandstones of the Jaisalmer basin.     

Petrography and major element geochemistry of the Permo-Triassic sandstones, central India: Implications for provenance in an intracratonic pull-apart basin

Detrital mode, composition of feldspars and heavy minerals, and major element chemistry of sandstones from the Permo-Triassic succession in the intracratonic Satpura Gondwana basin, central India have been used to investigate provenance. The Talchir Formation, the lowermost unit of the succession, comprises glacio-marine and glacio-fluvial deposits. The rest of the succession (base to top) comprising the Barakar, Motur, Bijori, Pachmarhi and Denwa formations, largely represent variety of fluvial depositional systems with minor fluvio-deltaic and fluvio-lacustrine sedimentation under a variety of climatic conditions including cold, warm, arid, sub-humid and semi-arid. QFL compositions of the sandstones indicate a predominantly continental block provenance and stable cratonic to fault-bounded basement uplift tectonic setting. Compositional maturity of sandstones gradually increases upwards from the Early Permian Talchir to the Middle Triassic Denwa but is punctuated by a sharp peak of increased maturity in the Barakar sandstones. This temporal change in maturity was primarily controlled by temporal variation in fault-induced basement uplift in the craton and was also influenced by climatic factors. Plots of different quartz types suggest plutonic source rocks for the Talchir sandstones and medium-to high-rank metamorphic plus plutonic source rocks for the younger sandstones. Composition of alkali feldspars in the Permo-Triassic sandstones and in different Precambrian rocks suggests sediment derivation from felsic igneous and metasedimentary rocks. Compositions of plagioclase in the Talchir and Bijori sandstones are comparable with those of granite, acid volcanic and metasedimentary rocks of the Precambrian basement suggesting the latter as possible source. Rare presence of high-K plagioclase in the Talchir sandstones, however, indicates minor contribution from volcanic source rock. Exclusively plagioclase-bearing metasedimentary rock, tonalite gneiss and mafic rocks are the probable sources of plagioclase in the Upper Denwa sandstones. Quartz-rich nature of the sandstones, predominance of K-feldspar over plagioclase and albite rich character of plagioclase in the sandstones is consistent with deposition in an intracratonic, pull-apart basin like the Satpura Gondwana basin. Composition of garnet and its comparison with that from the Precambrian basement rocks suggests mica-schist and amphibolite as possible sources. Predominance of dravite variety of tourmaline in the Permian sandstones suggests sediment supply from metasedimentary rocks. Presence of both dravite and schorl variety of tourmaline in subequal amount in the Triassic sandstones indicates sediment derivation from granitic and metasedimentary rocks. However, schorl-bearing rocks are absent in the basement complex of the study area. A-CN-K plot suggests granites, acid volcanic rock and meta-sediments of the basement as possible sources of the Talchir sandstones and metasedimentary rocks for the Barakar to Pachmarhi sandstones. The Denwa sandstones were possibly derived from K-feldspar-free, plagioclase-bearing metasediments, mafic rocks and tonalite gneiss. Chemical Index of Alteration (CIA) values suggest low intensity source rock weathering for the Talchir sandstones and higher intensity source rock weathering for the others. Various bivariate plots of major oxides composition of the sandstones suggest passive to active continental margin setting and even arc tectonic setting for a few samples.     

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.     

Petrographic and geochemical characteristics of Paleogene turbidite deposits in the southern Aegean (Karpathos Island,SE Greece): Implications for provenance and tectonic setting

The provenance and depositional setting of Paleogene turbidite sediments from the southern Aegean are investigated using petrography and whole-rock geochemistry. Petrography indicates that Karpathos Island turbidites are consisting of compositionally immature sandstones (graywackes–litharenites) derived from igneous (plutonic–volcanic), sedimentary, low-grade metamorphic and ophiolitic sources. The studied sediments probably reflect a mixing from an eroded magmatic arc and from quartzose, recycled sources. Major and trace element data are compatible with an acidic to mixed felsic/basic source along with input of ultramafic detritus and recycling of older sedimentary components. Geochemical data also reveal that the sediments have undergone a minor degree of weathering and no significant sediment recycling. Chondrite-normalized REE plots show a light REE enrichment (LaN/YbN ca. 7) and absence of significant negative Eu anomalies, indicating provenance from young undifferentiated arc material with contribution from an old upper continental crust source. Turbidite sedimentation probably took place in a continental island arc depositional setting as a result of subduction of a branch of Neotethys beneath a continental fragment of the Anatolide domain in Early Tertiary times. The relation of Karpathos turbidites with the Pindos foreland basin (Gavrovo and Ionian Zones of western Greece) remains problematic.     

陕南山阳地区刘岭群砂岩岩石地球化学特征及其构造背景分析

陕南山阳地区中晚泥盆世刘岭群位于秦岭造山带的商丹断裂带与山阳断裂之间。由于所处的特殊位置,刘岭群沉积特点及其盆地形成时期构造背景的确定,可以为秦岭地区古生代以来构造演化提供有价值的信息。岩石地球化学分析表明,刘岭群砂岩主要氧化物特征以SiO₂和K₂O含量较高为特点,具有较高的化学成熟度,反映出其碎屑物质可能来源于相对稳定的大陆源区或更老的沉积岩再旋回的沉积产物。砂岩的稀土元素LREE/HREE比值为3.61,属轻稀土中等富集;Eu/Eu^*值为0.77,属亏损型,与后太古代大陆地壳沉积岩总体演化特点相一致。主量元素氧化物、稀土元素及微量元素的多种图解和多种参数交叉分析,表明刘岭群沉积不具备前陆盆地堆积的特征。根据砂岩岩石地球化学的构造背景判别和物源区判别,结合沉积序列和沉积岩石学等分析,指示中晚泥盆世刘岭群碎屑岩应属于被动大陆边缘盆地沉积。     

PROVENANCE OF LOWER TERTIARY REDBEDS IN HOH XIL BASIN AND UPLIFT OF NORTHERN TIBET PLATEAU

PROVENANCE OF LOWER TERTIARY REDBEDS IN HOH XIL BASIN AND UPLIFT OF NORTHERN TIBET PLATEAU     

鄂尔多斯盆地子长油田杨家园则探区长6物源分析

通过对鄂尔多斯盆地东北部子长油田杨家园则探区延长组长6砂岩的骨架矿物、重矿物、阴极发光、泥岩的稀土元素特征等的研究,并结合盆地东北缘典型露头剖面的古水流方向实测,分析了长6沉积期的古水流与主要物源方向,探讨了源区母岩性质。结果表明,研究区长6沉积期的古水流与主要物源方向来自北东方向。源区母岩以变质岩为主,其次少量火成岩。该研究结果对鄂尔多斯盆地东北部延长组砂体时空展布分析、有利油气聚集区带预测以及对研究区下一步的油气勘探部署都具有重要的理论意义和实际参考价值。     

藏南古近纪甲查拉组物源分析及其对印度-欧亚大陆碰撞启动时间的约束

位于特提斯喜马拉雅北亚带的江孜地区古近纪甲查拉组角度不整合于晚白垩世宗卓组之上,系该地区最高(时代最晚)海相地层。运用岩石学和地球化学方法对其进行分析研究结果表明该组物源区主要为近源再旋回造山带,岩屑的母岩类型主要是岩浆弧成因的中性、中酸性安山质火山岩。新生代以前,特提斯喜马拉雅属于印度板块的被动大陆边缘,从特提斯喜马拉雅南亚带向北亚带显示了一种从浅水陆棚到深水盆地的变化,在侏罗-白垩纪时其陆源碎屑物主要是成熟度极高的石英砂岩,所以甲查拉组的碎屑物质只能来源于当时的冈底斯弧地区,所获有限的古水流证据也指示了这一点。从欧亚大陆侵蚀下来的碎屑物质被带到原印度大陆地区沉积,暗示该区的特提斯洋壳已经完全消失,印度与欧亚大陆在特提斯喜马拉雅中、东部产生了初始的陆-陆碰撞,其碰撞的启动时间为甲查拉组开始沉积的65 M a±。     

Provenance of Cretaceous sandstones in the Banda Arc and their tectonic significance

The provenance of Cretaceous sandstones in the Banda Arc islands differs from west to east. Sandstones in Sumba and West Timor contain significant amounts of feldspar (K-feldspar and plagioclase) and lithic fragments, suggesting a recycled to magmatic arc origin. In comparison, East Timor and Tanimbar sandstones are quartz rich, and suggest a recycled origin and/or continental affinity. Heavy mineral assemblages in Sumba and West Timor indicate metamorphic and minor acidic igneous sources and include a mixture of rounded and angular zircon and tourmaline grains. In East Timor, Babar and Tanimbar, an ultimate origin from a mainly acid igneous and minor metamorphic source is interpreted, containing a mixture of rounded and angular zircon and tourmaline grains.Detrital zircon ages in all sandstones range from Archean to Mesozoic, but variations in age populations indicate local differences in source areas. Sumba and West Timor are characterised by zircon age peaks at 80–100 Ma, 200–240 Ma, 550 Ma, 1.2 Ga, 1.5 Ga and 1.8 Ma. East Timor and Tanimbar contain 80–100 Ma, 160–200 Ma, 240–280 Ma, 550 Ma and 1.5 Ga zircon peaks. Most populations are also common in Triassic and Jurassic formations along the Outer Banda Arc and in many other areas of SE Asia. However, the abundance of Jurassic and Cretaceous populations was unexpected. We interpret Cretaceous sandstones from Sumba, Timor and Tanimbar to have been deposited in SE Sundaland. Syn-sedimentary Cretaceous (68–140 Ma) sources are suggested to include the Schwaner Mountains in SW Borneo and Sumba. Material derived mainly from older recycled sediments that had their main sources in the Bird's Head, Western and Central Australia, and local sources close to Timor.     

孙吴-嘉荫盆地白垩系淘淇河组-太平林场组砂岩主量元素的地球化学特征

沉积盆地中砂岩的地球化学特征主要受物源区控制,碎屑岩的地球化学成分可揭示沉积物的地质信息.笔者通过对孙吴-嘉荫盆地白垩系淘淇河组-太平林场组砂岩的主量元素地球化学特征分析,结合砂岩薄片碎屑成分统计表明:淘淇河组-太平林场组时期物源区的大地构造背景主要为活动大陆边缘,包括大陆岛弧和大洋岛弧.物源区母岩类型主要为花岗岩,中酸性火山岩及低级变质岩.盆地不同位置物源区的大地构造背景和母岩类型有所不同.结合区域地质资料综合分析认为:在淘淇河组-太平林场组沉积时期,小兴安岭仅在太平林场组时期不是盆地主要物源区,而佳木斯地块一直是盆地东部的一个主要物源区.     

Provenance of Triassic and Jurassic sandstones in the Banda Arc: Petrography,heavy minerals and zircon geochronology

Quartz-rich sandstones in the Banda Arc Islands are thought to be equivalent of Mesozoic sandstones on the Australian NW Shelf where they are important proven and potential reservoirs. Previous studies suggested that rivers draining Australia provided most of the sediment input and there have been suggestions of a northern provenance for some Timor sediments. We present results from a provenance study of Triassic and Jurassic sandstones of the Banda Arc between Timor and Tanimbar, which used several methodologies, including conventional light and heavy mineral point counting, textural classification and laser ablation (LA-ICP-MS) U–Pb dating of detrital zircons. Most sandstones are quartz-rich and detrital modes suggest a recycled origin and/or continental affinity, consistent with an Australian source. However, many of the sandstones are texturally immature and commonly contain volcanic quartz and volcanic lithic fragments. In the Tanimbar Islands and Babar, acid igneous material came from both the Australian continent and from the Bird's Head, whereas sandstones in Timor have a greater metamorphic component. Heavy mineral assemblages are dominated by rounded ultra-stable minerals, but mixed with angular grains, and indicate an ultimate origin from acid igneous and metamorphic sources. Detrital zircon ages range from Archean to Mesozoic, but variations in age populations point to differences in source areas along the Banda Arc both spatially and temporally. Significant zircon populations with ages of 240–280 Ma, 1.5 Ga and 1.8 Ga are characteristic and are also common in many other areas of SE Asia. We interpret sediment to have been derived mainly from the Bird's Head, Western and Central Australia in the Triassic. In the Jurassic local sources close to Timor are suggested, combined with recycling of NW Shelf material.     

西藏白朗南部地区三叠纪地层沉积环境及物源

综合露头剖面、砂岩碎屑组分、地球化学、阴极发光等资料的研究,对西藏白朗地区南部三叠系沉积环境及物源开展了研究。该区三叠纪地层以灰黑色泥岩、浅灰白色石英砂岩、长石石英砂岩、灰色灰岩为主,沉积背景为拉轨岗日被动陆缘盆地的浅海-半深海环境。碎屑岩及其地球化学分析结果反映,物源总体来自克拉通内部。阴极发光结果表明,物源区石英主要为变质成因,次为火成岩成因。综合判定,研究区该套地层为下—中三叠统吕村组和上三叠统涅如组,物源区来自南部高喜马拉雅基底杂岩带。     

西藏扎布耶盐湖超大型B、Li矿床成矿物质来源研究

扎布耶盐湖位于西藏高原腹地,是一个现代盐湖矿床。对扎布耶地区地球化学背景的研究表明:变质岩及蚀变岩石中硼锂含量很高以及电气石脉的出现,暗示着扎布耶地区深部曾产生含硼锂高的热流体;沉积岩中除晚石炭世砂岩含硼锂稍高外,其他岩石均低于同类岩石的平均含量;火山岩中除早白垩世基性岩的硼锂含量高于基性岩平均含量外,其他均很低;该区大量发育的第四纪钙华含硼锂非常高,表明早期的热水系统曾提供过大量的成矿物质;河流及泉水中的硼锂含量是世界河水平均含量的数倍至数百倍,表明地表和近地表条件下的水-岩相互作用的产物也是成矿物质来源之一。