Monocrystalline Quartz Grains Research Articles

Provenance Analysis and Diagenesis Using Integrated SEM-Cathodoluminescence and Optical Microscopy for the Sandstones of the Pirispiki Formation, Kurdistan Region, Northern Iraq

The paragenetic history and provenance of framework grains in marginal marine and deltaic sandstones of the Pirispiki Formation in two sections, (Ora and Kaista), northern Iraq were examined. This was achieved using an integrated approach employing scanning electron microscopy-cathodoluminescence (SEM-CL), and optical microscopy. The Pirispiki Formation is lithologically characterized by alternating layers of thin- and thick-bedded sandstones. These were intercalated with thin laminae of grey-black shale. Petrographic analysis revealed that the dominant detrital grains in the mature quartz arenite sandstone were monocrystalline quartz grains with undulose extinction. The diagenetic analysis of the sandstones documented several processes that occur in three distinct stages. The SEM-CL technique enabled the identification of two distinct quartz overgrowth phases. Quartz cementations are of two types, the earliest phase and the most significant by volume is the Q1 cement characterized by dark non-luminescence which led to the destruction of most of the primary pores and the healing of mechanically induced cracks. Q2 cement is formed after major compaction and is characterized by bright luminescence with sector zoning, revealing an intricate SEM-CL zonation. CL revealed five special textures within detrital quartz grains including healed fractures and zoning. The provenance of the detrital quartz grains indicated the dominance of plutonic and metamorphic sources, with trace amounts originating from volcanic sources. These were mostly derived from the Bitlis Massif Zone in Turkey.

Temporal variation in sandstone composition of Miocene Jatiluhur Formation in the Bogor Trough, West Java, Indonesia

Bogor Trough in the West Java are typified by turbidity deposits with the source are mostly characterized by volcanoclastic materials from the southern area. The Trough actually receipt the sediment from both volcanoclastic materials from the south and continental source from the north. But, the discussions of sediments in term of composition and temporal variation are rare to be reported, especially the sediments from the north. This manuscript intends to discuss the temporal variation in detrital compositional and depositional facies of the Neogene sediments that delivered from the north (i.e., Sundaland) into the Bogor Trough, which is represented by Miocene Jatiluhur Formation.
 A total of 36 selected samples have been taken for identifying the minerals using a polarization microscope. Modal analysis of the Gazzi-Dickinson method was applied for this provenance study of sandstones samples, which are consisting largely of quartz and feldspar, then sedimentary rock and volcanic rock fragments, glaucony, mud chips and skeletal fragments.
 Sundaland, a continental block highland area in the north, is interpreted to have been the provenance of sediments of the Jatiluhur Formation, which is also considered to be the source area for the Paleogene sediments. Granitic igneous rocks are interpreted as the source of dominance of monocrystalline quartz grains, or the product of long-distance transport of polycrystalline quartz from metamorphic rocks
 But, however late Miocene samples (upper part of formation) represent that the size and amount of glauconite grains are increasing, and texturally mud supported. Volcanic rocks materials are also observed. The upper part of Jatiluhur Formation records the starvation of sediment discharge into the basin, which has been also promoted for development of carbonate reef Klapanunggal Formation in the self-margin setting, and suggesting that the basin have directly received or indirectly some contemporaneous volcanic provenances sediment from the southern area.

Trans-Saharan Belt Provenance: A Potential Source for the Ordovician Succession of the Balkan Terrane (Svoge Unit) - Clues from LA-ICP-MS Detrital Zircon Dating Analysis

Two sandstone samples from the upper and lower part of the Ordovician succession of Svoge Unit were analyzed in order to determine their detrital zircon U–Pb age spectra using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). One sample was collected from the Hirnantian siliciclastic glaciomarine deposits of the Sirman Formation. The other sample is amiddle Darriwilian sandstone from the lower half of the Grohoten Formation. Additionally, micropetrographic studies were performed. They are composed predominantly of detrital monocrystalline quartz grains with uniform or rarely undulose extinction and only sporadically presented feldspar grains, muscovite flakes and single rock fragments. The heavy mineral assemblages are also characterized mostly by detrital zircon. As suggested from previous studies of the Hirnantian glaciomarine deposits of Sirman Formation, the provenance of siliciclastic material was most probably associated with sedimentary recycling of maturesands deposited across the North Gondwana Platform. Multi-dimensional scaling statistical technique allowed a reliable objective identification of the potential source areas in Northern Africa and palaeogeographic reconstructions were made. Both samples are close to the Trans-Saharan Belt provenance, which is the most probable source for the detrital component. Our data supportthe idea proposed by previous researchers that the present-day position of some of these terranes implies significant dextral strike-slip displacement, probably due to the movement on the Pangea megashear during the Carboniferous and Permian.

Sedimentary environment and tectonic setting of the clastic formation of the Tanjianshan Group in the Tuomoerrite area, North Qaidam

柴北缘构造带断续出露的寒武-奥陶纪滩间山群火山-沉积岩系是早古生代时期原特提斯洋俯冲造山作用的产物，也是中国西部块状硫化物和造山型金矿床的重要含矿岩系。前人已对滩间山群火山岩组开展了大量的地球化学和同位素年代学研究，而碎屑岩组的沉积序列和沉积相研究相对薄弱。我们在柴北缘托莫尔日特地区地质填图过程中，对该地区的滩间山群碎屑岩组开展了系统的沉积组合序列和沉积相研究。托莫尔日特地区滩间山群碎屑岩组是由富含火山碎屑物质的含砾砂岩、砂岩、粉砂岩、泥岩、沉凝灰岩、硅质凝灰岩、硅质岩及少量砾岩共同组成。可分为下岩性段和上岩性段，其中下岩性段为一套形成于海底扇外扇环境以沉凝灰岩为主的沉积组合；上岩性段包含海底扇内扇、中扇和外扇沉积，且以中扇环境的沉积为主。垂向上，它们呈现出粒度向上逐渐变细特征；空间上，具有向北西方向火山物质成分逐渐增多、砾岩和砂岩厚度变薄且砾岩消失的变化特征。砂岩主要为岩屑长石杂砂岩，其中岩屑主要是安山岩和少量玄武岩、英安岩、凝灰岩；长石主要为斜长石；石英碎屑相对缺失。砾岩中砾石以安山岩和硅质岩为主，并含有少量灰岩和凝灰岩砾石。底冲刷面、正粒序、平行层理和波纹层理等沉积构造普遍发育，呈现出典型的浊流沉积特征；同时在局部露头见有滑塌构造和波痕。区域上，这套沉积组合序列位于寒武-奥陶纪岛弧火山岩的南侧；古水流分析显示，它们的碎屑物质主要来自于其北东方向。这些结果表明，柴北缘构造带东段的滩间山群碎屑岩组是一套成熟度极低且与寒武-奥陶纪岛弧火山活动密切相关的沉积组合。;Volcano-sedimentary system of the Cambrian-Ordovician Tanjianshan Group in the northern margin of Qaidam basin was formed by the subduction of the Proto-Tethys Ocean during Early Paleozoic and hosted massive sulfides and orogenic gold deposits in western China. Much attention had been paid to geochemistry and isotopic dating of the volcanic Formation of the Tanjianshan Group, but the sedimentary sequence and facies of the associated clastic rocks received less care. Systemic studies on the sedimentary sequence and facies in the processes of the geological mapping demonstrate that the clastic Formation in the Tuomoerrite area consists of pebbly sandstone, sandstone, siltstone, mudstone, tuffite, siliceous tuff, chert and minor conglomerate. This formation can be subdivided into two lithologic units. The lower unit is mainly dominated by tuffite deposited in the lower submarine fan environment, whereas the upper unit is deposited in the upper, mid, and lower fan environments. In contrast, the rock assemblages of the upper unit are mainly composed of the mid-fan deposits. The upper unit is characterized by fining-upward sequence and increasing abundance of volcanic composition northwestward, but the thickness of sandstones decreases and conglomerate disappears to northwest. Sandstones mainly comprise lithic greywacke. Lithic fragments contain andesite, basalt, dacite, and minor tuff and limestone. Feldspar fragments are dominated by plagioclase grains, and less monocrystalline quartz grains with an igneous origin occur in several samples. Clasts of conglomerates are dominated by angular andesite, chert and minor limestone and tuff. Irregular basal erosional surface, normal grading, parallel laminations and ripples are widespread show typical of turbidite. Slumping folds and wave marks can also be observed in the local outcrops. Regionally, volcano-clastic rocks distributed in the southern margin of Cambrian-Ordovician Keke island arc with a southwestward paleocurrent. These results demonstrate that the clastic formation is closely related to the Cambrian-Ordovician island arc.

Controls on the compositional framework and petrogenesis of Early Cretaceous first cycle quartzose sandstone, North Gondwana

Recent advances in sedimentary research have shown that quartz sandstones are scarce in the global geologic record and prolonged sediment transport does not automatically produce mineralogically mature sediments. Published data are based mainly on Cambro-Ordovician arenites. This paper discusses the formational controls of early Cretaceous syn-rift quartzose from northern Gondwana based on integrated petrographic, mineralogic, and electrofacies proxies on the Upper Sarir Sandstone Formation, Sirte Basin, Libya. The study aimed to understand the compositional framework and construe the sedimentological processes that produced the quartz-rich sandstones. Acquired samples (n = 40) from three boreholes (N8-97, N7-97, and N4-97) were subjected to petrographic analysis, x-ray diffractometry, and variable pressure scanning electron microscopy with energy dispersive x-ray spectrometry. Qualitative and quantitative datasets indicate that the mean framework composition (Q97F0L3) of the sample is quartz-dominated and primarily detrital, although diagenetic imprints, mostly quartz cementation, quartz overgrowth, and other authigenic precipitates, are present. Evidenced by the predomination of monocrystalline quartz grains (99.10%) over the polycrystalline type (0.90%), the dominance of non-undulatory extinction (72.50%), and noticeable euhedral crystals, the compositional framework of the studied quartzose reflects a predominant plutonic provenance with some metamorphic inputs. The possibility of significant sediment reworking is ruled out based on short to moderate transport distance (~100 km) interpreted from the interplay of textural parameters, depositional model, and paleogeography. A humid paleoclimate alongside its associated rigorous chemical weathering is constrained as the dominant control in the formation of the Upper Sarir quartzose sandstone from a dominant craton interior provenance. These conditions probably produced other early Cretaceous arenitic sandstones in other reaches of North Gondwanaland.

Diagenesis and Porosity Evolution of the Pachmarhi Sandstones (Early Triassic), Satpura Gondwana Basin, Central India

This study deals with the diagenetic history of the Pachmarhi Sandstones of Satpura Gondwana Basin, Central India. The sandstones are classified as quartz-arenite and sub-arkose type. Monocrystalline quartz grains dominate the detrital mineralogy followed by polycrystalline quartz grains, feldspars (more alkali-feldspar than plagioclase), rock fragments, detrital mica and heavy minerals. The diagenetic signatures observed in the Pachmarhi Sandstones include mechanical compaction, cementation (Fe-oxide, quartz overgrowths, calcite, matrix and clay minerals), replacement and dissolution of feldspar and calcite cement. The most commonly observed type of secondary porosity is dissolution of feldspars. The porosity loss is mainly due to cementation by pore occlusion and by early stage of mechanical compaction. In addition, several clay minerals occurred as pore-filling and pore-lining cements. The nature of various types of grain- to grain contacts suggests early cementation and consequent minor compaction. Among the various cements, calcite is the earliest followed by iron oxide while silica cementation occurred probably at a late stage. The carbonate cement formed during burial by dissolution and re-precipitation represents redistributed calcite which was buried with the sandstone. The iron cement was perhaps derived from weathering and leaching of ferromagnesian minerals of overlying Deccan traps. Silica cement was derived from the corrosion of quartz and feldspar grains. Types of grain contacts, minus-cement porosity and porosity reduction indicate a shallow depth of burial conditions for these sandstones.

Surface textures of quartz and ilmenite grains from dune and beach sands of the Gulf of Mexico Coast, Mexico: Implications for fluvial, aeolian and marine transport

Surface textures of quartz and ilmenite grains provide an insight in assessing current mechanical, chemical and mechanical-chemical processes in dune and beach sands of the Gulf of Mexico Coast (GMC) Mexico. The GMC area produces hybrid sands enriched in monocrystalline quartz and ilmenite-free grains. Quartz grains are observed in all dunes and beach localities of the central GMC close to the Trans-Mexican Volcanic Belt characterized by large conchoidal fractures (>100 μm), angular to subangular outlines, arcuate steps, high relief, and sharp edges associated with fluvial transport. Aeolian quartz features like meandering ridges, upturned plates, bulbous edges and adhering particles on quartz are only present in some GMC sites, whereas marine surface textures like straight and curved grooves are sparse. Chemical surface textures on quartz and ilmenite are a consequence of silica saturated low-energy subaqueous conditions and subaerial exposure, diagenesis and intermediate weathering processes in the dunes and beach sands. Ilmenite grains are common in all studied localities of the GMC, characterized by large conchoidal fractures (>100 μm), angular to subangular outlines, flat cleavage surfaces, arcuate steps and high relief. In some ilmenite grains, upturned plates, meandering ridges, bulbous edges and abrasion fatigue characterize aeolian surface features. Straight and curved grooves only characterize marine surface textures. To assess the prevailing transport mechanisms along the GMC, quartz and ilmenite grains from dunes and beach sands were selected based on surface texture observations. Our findings suggest that quartz and ilmenite grains are primarily transported and deposited along the coast by riverine input, a second-cycle of aeolian transport onshore, and recycling by marine longshore currents and waves.

OH defects in quartz as a provenance tool: Application to fluvial and deep marine sediments from SW Japan

Hydrogen-related point defects (OH defects) in the crystal lattice of detrital, monocrystalline quartz have been proposed as an indicator to distinguish different sediment sources, making it a potential tool for provenance analysis. This study tests this novel technique on samples from SW Japan by comparing the results of OH defect analyses with those of “classical” provenance studies. OH defects of 188 detrital, monocrystalline quartz grains from five rivers (Fuji, Tenryu, Nagara, Yoshino, and Shimanto) and four offshore wells drilled in the Nankai Trough area (ODP site 1177; IODP sites C0002, C0007, C0012) are characterized using Fourier-transform infrared (FTIR) spectroscopy. Considerable differences in OH defect concentrations are identified between individual river samples. A general increase of values from east to west is observed. Possible links to the respective source geology are established. Very low OH defect contents (<1 wt. ppm water) of sediment from the Fuji and Tenryu rivers may be a result of high deformation and exhumation in the Izu-Honshu collision zone. Moderate to high OH defect contents of Nagara and Yoshino river samples (up to 50 wt. ppm water) are similar to the values of the global average in continental crust, possibly due to a mixing of various source lithologies. High and very diverse OH defect contents of Shimanto River sediments (up to 211 wt. ppm water) are likely an effect of extensive sediment reworking and mixing in the Nankai accretionary wedge. The OH defect signal is shown to be traceable through the offshore sedimentary record. In the western Shikoku Basin (ODP site 1177), turbidite deposits at 15 Ma and 7 Ma show a very similar signal as recent Shimanto river sediment, whereas eastern Shikoku Basin sediments (IODP Site C0012), at 15 Ma and 6 Ma strongly resemble present day Nagara and Yoshino river sediments. Sediments deposited in the Nankai trench wedge at 1 Ma (IODP Site C0007) indicate a shift towards lower OH defect concentrations. This may be due to increased, trench parallel sediment flux from the low-OH defect Fuji and Tenryu river sources, as proposed by previous studies. This study presents the first OH defect dataset in detrital quartz from rivers and offshore drill sites in a subduction zone environment, introducing OH defects as a new useful tool for sediment provenance analysis in active convergent margin settings.

Sources of quartz grains influencing quartz cementation and reservoir quality in ultra-deeply buried sandstones in Keshen-2 gas field, north-west China

Quartz cementation is a critical factor in the reservoir quality of ultra-deeply buried sandstones because of the high temperature and high-pressure at great depths. Therefore, determining the main influences retarding the growth of the quartz overgrowths is important for predicting the sweet spots of tight gas sandstones. The vast Keshen-2 gas field in Kuqa Depression is typical of such ultra-deep gas fields, despite the porosity and permeability of the target sandstones in the Lower Cretaceous Bashijiqike Formation being less than 10% and 0.5 md, respectively. The main gas reservoirs had been buried previously to a depth of 7000 m, with the maximum fluid temperature approaching 160 °C, in which authigenic quartz cements are extremely common. The heterogeneity of the physical properties and quartz cementation was investigated using core analysis, log interpretation, thin sections and scanning electron microscopy (SEM). The findings indicated that the Bashijiqike Formation could be stratified into upper porous and lower tight zones. The porosity of the sandstones in the upper zone is generally higher than 5% and abundant polycrystalline quartz grains are present. However, the reservoirs in the lower zone with low overall porosity values below 5%, contain high contents of monocrystalline quartz grains. The polycrystalline quartz grains show brown cathodoluminescence that indicates mainly a metamorphic source from the southern Tianshan provenance which is located to the north of Keshen-2. The monocrystalline quartz grains display primarily blue to violet luminescence colours, suggesting an origin from volcanic or plutonic mother rocks of the Wensu and Kuluketage provenance areas, situated to the southwest and southeast, respectively. The monocrystalline quartz grains are surrounded commonly by quartz overgrowths, whereas the polycrystalline quartz grains are cemented slightly. The presence of polycrystalline quartz grains hampers potential quartz overgrowths—the critical reason preserving the intergranular pores in the ultra-deeply buried sandstones of this gas field. Accordingly, we propose that the metamorphic quartz grain content is the main factor inhibiting quartz cementation, which preserves reservoir quality. This knowledge is conducive to determining the growing mechanism of high-quality reservoirs and predicting the sweet spots of gas production in the ultra-deeply buried sandstones.

Lower Paleozoic reservoir zonation into different flow units using turbulence factor and their relations to diagenesis

Surface Lower Paleozoic sandstone samples were collected from southeast central Sinai. These samples subjected to petrophysical measurements which are porosity and permeability. It is known that turbulence factor (β) is a good tool to describe turbulent flow level, hence it was used to detect the flow properties distribution that corresponds to the nature of the pore system, so turbulence factor (β) was correlated with porosity, permeability, and reservoir quality index using many equations, where porosity correlation shows the presence of three groups having same porosity ranges but correspond to different values of turbulence factor, this refers to the presence of different flow zones. Porosity–permeability relation confirmed also the presence of similar three groups, where there are nearly same porosity ranges but with different permeability values. Consequently, samples with nearly same porosity values and representing the three groups were selected for capillary pressure by mercury injection to reveal the flow properties that characterize each group. Capillary pressure results confirmed that each group has their own pore system and flow regime. Petrography was done by optical polarizing microscope (OPM) through thin sections. The results indicated that the studied sandstone is composed mainly of quartz arenite microfacies of fine, angular to subrounded, moderately well sorted monocrystalline quartz grains. There are several features indicating that the investigated sandstones have been subjected to diagenesis processes. Diagenetic events identified in these sandstones include considerable compaction during burial diagenesis at higher temperatures and low flow rates, cementation by clay minerals and iron oxides, dissolution and alteration of unstable clastic grains, and tectonically induced grain fracturing. Unstable clastic grains like feldspars suffered considerable alteration to kaolinite when exposed to meteoric water of low ionic strength near the surface. The distribution of this kaolinite rather than the post-depositional iron oxides in pores of the studied sandstone leaded to differentiating these sandstones into three different flow units. This zonation indicates that the turbulence properties are proportional to the diagenetic effects inside the pores.

Petrography and geochemistry of sandstone samples of Vischkuil formation, Karoo Supergroup, South Africa

Petrography and geochemistry of sandstones of Vischkuil formation in the Ecca Group of the Karoo Supergroup of South Africa was investigated to evaluate the petroleum potential of its reservoir rock. The petrographic analysis showed that the sandstones were poorly to moderately sorted with evidence of angular to sub-angular grains. The sandstones are lithic arenite. Diagenetic processes on the sandstone include physical and chemical compaction as seen from the straight grain contacts and dissolution of the quartz grains. There is an evidence of pore space reduction by the rearrangement and cementation by silica, calcite and clay minerals. The petrographic analysis also revealed that there is dominance of monocrystalline quartz grains and evidence of cratonic setting derivation. The chemical alteration index ranged from 52.96 to 65.5 %, an indication of a moderate weathering at the source area before deposition. The samples are texturally immature, which indicate poor storage capacity for fluids.

Mineralogy and grain morphology of the aeolian dune sand of Toshka area, southeastern Western Desert, Egypt

Abstract This work investigates the mineralogical properties and the morphology of aeolian quartz sand in the Toshka dune area, southeastern Western Desert of Egypt. The dunes are composed mostly of subangular to subrounded fine to medium quartz sands together with minor proportions of feldspars and lithic fragments. Significant roundness variations are observed both between different dune types and within the dune sites. Barchan sands are the most rounded, whilst sand shadows are angular and fine. Barchans are also relatively enriched in polycrystalline quartz, where most of these grains are more rounded and more durable than monocrystalline quartz. Roundness characteristics of the Toshka sands are considerably managed by their grain size as medium quartz grains are more rounded than the finer ones. Angularity is a characteristic property of most monocrystalline quartz grains that exhibit undulose extinction. This maintenance of undulose extinction in quartz perhaps as a result of less stability and minimal transport from the source in the vicinity of the dune fields, as shown by the increase of angularity of quartz and short-distance transfer of these grains. These Toshka sand grains also show signs of a fluvial transportation signature. The analysis of grain surface features by scanning electron microscope (SEM) performed on dune sand grains from the Toshka area showed that quartz grains demonstrate a variety of surface textures indicating mechanical and chemical processes developed during transportation of these grains in subaqueous and aeolian environments, respectively, reflecting the mixed mode of formation of these dunes.

Petrography and geochemistry of lower Paleozoic sandstones, East Sinai, Egypt: Implications for provenance and tectonic setting

Petrography, mineralogy and chemical analyses were combined to investigate the lower Paleozoic sandstones at Wadi El-Quseiyeb area, East Sinai. They are mainly classified texturally as silty sandstones, sandstones and clayey siltstone. Their average modal composition (QFL, 87:11:2), classifies them as quartz arenite and arkosic arenite, with high proportions of quartz, monocrystalline quartz grains, more potash feldspar than plagioclase and a low plagioclase/total feldspar ratio ( P/ F < 0.2). High SiO 2, K 2O > Na 2O, and low Fe 2O 3 + MgO values revealed by chemical analyses are consistent with the modal data. Other criteria include elevated Ba and Sr contents and depletion in the ferromagnesian elements. The petrography and geochemistry suggest a stable continental (passive) margin or intracratonic basin, analogous to that of an Atlantic-type continental shelf. Also, they reflect a stable craton interior source, devoid, to a large extent, of basic debris and ultimately derived from a low-lying granite-rich Precambrian craton. Chemical index of alteration (CIA) and the Plagioclase index of Alteration (PIA) values range from 57.2 to 93.0 and from 79.7 to 94.6, respectively. However, most samples have values more than 60, suggesting a moderate to relatively high degree of alteration (weathering) in the source area.

Age of Initiation of the India‐Asia Collision in the East‐Central Himalaya

Abstract We document the stratigraphy and provenance of the lower Tertiary terrigenous sections in the Zhepure Shan region of the Tethyan Himalaya, southern Tibet, using petrographic and geochemical whole‐rock and single‐grain techniques. The Cretaceous–early Tertiary shelf deposits of shallow marine carbonates and siliciclastics of the former Indian passive margin near the western end of the Zhepure Shan are conformably overlain by lower Tertiary clastic rocks. Sandstones in the Jidula Formation (Paleocene) mostly contain monocrystalline quartz grains of cratonic origin. In contrast, significant amounts of immature framework grains with a distinct ophiolitic and volcanic arc influence are present in the Youxia (Early Eocene) and Shenkeza (post–Early Eocene) formations. Major, trace, and rare earth element concentrations in both sandstones and shales complement the petrographic data and indicate that the source of the Jidula Formation consisted primarily of quartzose basement rocks, probably of Indian con...

Early Cretaceous stratigraphy, depositional environments, sandstone provenance, and tectonic setting of central Tibet, western China

Research Article| September 01, 2004 Early Cretaceous stratigraphy, depositional environments, sandstone provenance, and tectonic setting of central Tibet, western China Kai-Jun Zhang; Kai-Jun Zhang 1Guangzhou Institute of Geochemistry, Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510640, China2State Key Laboratory of Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China Search for other works by this author on: GSW Google Scholar Bang-Dong Xia; Bang-Dong Xia 3Department of Earth Sciences, Nanjing University, Nanjing 210093, China Search for other works by this author on: GSW Google Scholar Guan-Min Wang; Guan-Min Wang 4Department of Resources, University of Petroleum, Dongying, Shandong 257062, China Search for other works by this author on: GSW Google Scholar Yong-Tie Li; Yong-Tie Li 5Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Beijing 100083, China Search for other works by this author on: GSW Google Scholar He-Fei Ye He-Fei Ye 5Research Institute of Petroleum Exploration and Development, PetroChina Company Limited, Beijing 100083, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (2004) 116 (9-10): 1202–1222. https://doi.org/10.1130/B25388.1 Article history received: 21 Apr 2003 rev-recd: 27 Nov 2003 accepted: 29 Dec 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kai-Jun Zhang, Bang-Dong Xia, Guan-Min Wang, Yong-Tie Li, He-Fei Ye; Early Cretaceous stratigraphy, depositional environments, sandstone provenance, and tectonic setting of central Tibet, western China. GSA Bulletin 2004;; 116 (9-10): 1202–1222. doi: https://doi.org/10.1130/B25388.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The period following Late Jurassic continental collision but preceding Late Cretaceous–Cenozoic arc magmatism represents a significant, yet poorly understood tectonic transition in central Tibet, western China. The Asa basin (31°00′–32°40′, 84°30′–87°05′) in central Tibet, which crosses the southern margin of the Qiangtang block, the Bangong-Nujiang suture zone, and the northern half of the Lhasa block, is characterized by up to 5000 m of continental-marine clastic-carbonate sediments and is ideally positioned to provide constraints on this transition. Sedimentary and volcanic data from recent field studies suggest that contraction controlled Berriasian-Valanginian tectonics, whereas back-arc extension may have controlled Hauterivian–Early Cenomanian basin evolution.Berriasian-Valanginian strata occur over the northern half of the Asa basin (approximately north of 31°40′) and unconformably overlie a varied basement. Sediment transport and fining directions are generally toward the south. The sandstones (Q78F11L11, Qm72F11Lt17, Qp38Lvm8Lsm54) in the central Bangong-Nujiang suture zone are dominated by monocrystalline quartz grains with undulose extinction but also contain abundant chert grains and some ultrabasic lithic fragments and radiolarian fragments. Hauterivian–Lower Barremian strata are characterized by siliciclastic rocks deposited in high-energy tidal environments, and barrier-bank skeletal bioclastic grainstone and wackestone. Intraformational limestone breccia or conglomerate and bimodal volcanic rocks are in places found within the sedimentary sequences in the southern margin of the basin (approximately south of 31°35′). Sandstones (Q54F20L26, Qm45F20Lt35, Qp20Lvm59Lsm21) are characterized by complex derivations from both recycled orogen and volcanic arc provenances. Widespread thick carbonate is a characteristic feature of Upper Barremian–Lower Cenomanian lithofacies, possibly formed in both restricted platform and platform interior environments. Lithic fragments in the sandstones (Q34F24L42, interbedded Qm33F24Lt43, Qp3Lvm87Lsm10) with the carbonates predominantly reflect volcanic source areas (65%).The Berriasian-Valanginian sequence is interpreted to represent molasse sediments from a northern orogen and indicates that the collision between the Qiangtang and Lhasa blocks could have extended into the Valanginian. The change from orogenic to magmatic arc source areas for sandstones during the beginning of the Hauterivian, along with a coeval extensive marine transgression in central-southern Tibet, normal faulting, and rich intercalations of bimodal volcanic rocks, are interpreted to be related to back-arc extension of the Gangdese arc during the Middle Cretaceous (ca. 120–95 Ma). This may have occurred in response to a rollback of the Tethyan oceanic slab. During the Middle Cretaceous, the entire southern Eurasian margin could have been characterized by a series of back-arc rift basins (including those in Kohistan and Ladakh). Some basins may have been floored by oceanic crust whereas others remained underlain by continental or transitional basement, much like the present western Pacific margin. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Cenozoic history of the Himalayan-Bengal system: Sand composition in the Bengal basin, Bangladesh

Stratigraphic sequences preserved in the Bengal basin provide detrital information that documents a significantly older history of the eastern Himalaya than that available from Ocean Drilling Program and Deep Sea Drilling Project cores recovered from the Bengal fan. The Bengal basin, formed as a result of the Himalayan collision, is located at the juncture of the Indian craton to the west, the Shillong massif and the Himalayan belt to the north, and the Indo-Burman ranges to the east. Modal analyses of Eocene and Oligocene sandstones of the Cherra, Kopili, and Barail Formations document compositions that are dominated by subangular monocrystalline quartz grains with scarce to no feldspar grains, and few lithic fragments (Cherra and Kopili: Qt 99 F 1 L 0 ; Barail: Qt 90 F 3 L 7 ; Qt—total quartz, F—feldspar, L—lithic fragments). These compositions are similar to sands derived from the Indian craton, suggesting that they underwent intense chemical weathering, likely in a source with low relief and considerable transport. Himalayan tectonism during this time was probably significantly more distant from the Bengal basin than at present. Sandstones of the Miocene Surma Group (Bhuban and Boka Bil Formations) are rich in feldspar grains, argillite, and very low-grade metamorphic lithic fragments (Bhuban: Qt 66 F 15 L 19 ; Boka Bil: Qt 57 F 23 L 20 ) relative to older sandstones, suggesting onset of uplift and erosional unroofing in the eastern Himalaya, and initiation of stream systems supplying orogenic detritus to the Bengal basin. Sands of the upper Miocene to Pliocene Tipam Group and the Pliocene–Pleistocene Dupi Tila Sandstone contain abundant argillitic and low- to medium-grade metamorphic lithic fragments and feldspar grains (Tipam: Qt 61 F 19 L 19 ; Dupi Tila: Qt 70 F 13 L 17 ), suggesting continued orogenic unroofing. These younger sands are rich in potassium feldspar (P/F=0.30, 0.20) relative to plagioclase (P)-rich Bhuban and Boka Bil sandstones (P/F=0.66 and 0.48), suggesting a granitic source, probably the Miocene leucogranites of the High Himalayan Crystalline terrane. These results document for the first time contrasts in orogenic history recorded in the Bengal system vs. western Himalayan foreland basins. Sands deposited in the Bengal basin are generally more quartzose and less lithic than those from the western Himalayan foreland basins, and pre-Miocene strata in the Bengal system show little to no evidence of orogenic activity. In part, this probably reflects west to east progression of the Himalayan collision, but it probably also results from sedimentary systems propagating southward, ahead of the advancing mountain belt as it has been consuming the remnant ocean basin trapped between the Indian craton and the Burmese block.

Marine and Nonmarine Gas-Bearing Rocks in Upper Cretaceous Blackhawk and Neslen Formations, Eastern Uinta Basin, Utah: Sedimentology, Diagenesis, and Source Rock Potential

The Upper Cretaceous Blackhawk and Neslen Formations in the eastern Uinta basin contain large amounts of thermogenic gas that was generated from interbedded humic-rich source rocks. The geometry and distribution of hydrocarbon source and reservoir rocks are controlled by depositional environment. The Blackhawk, composed of laterally extensive sandstone and locally interbedded carbonaceous siltstone and minor coal, reflects deposition in nearshore marine and backshore environments. The Neslen contains organic-rich siltstone and mudstone with lesser amounts of carbonaceous shale, coal, and lenticular sandstone that formed in coastal and lower alluvial-plain depositional settings. Potential reservoir sandstones are composed dominantly of monocrystalline quartz grains and sedimentary lithic fragments. Mechanical compaction during early burial was followed by the precipitation of quartz, carbonate, and barite later in the burial history. Variations in porosity and permeability (2-10%; < 1 md) reflects the presence of authigenic clay, mineral cements, and dissolved lithic grains. Natural fractures, cemented with carbonate, barite, and kaolinite, occur locally. Active hydrocarbon generation occurred in the Neslen and Blackhawk during the Oligocene and Miocene when these units were near their maximum burial depth and temperature. The rate of hydrocarbon generation decreased from the late Miocene to the present, owing to widespread cooling that occurred in response to regional uplift and erosion associated with the development of the Colorado Plateau. Temporally equivalent rocks in other areas of the basin may have experienced similar diagenetic and hydrocarbon generation histories.

Quantitative Petrographic Analysis of Cretaceous Sandstones from Southwest Montana: ABSTRACT

The Albian Blackleaf Formation and the Cenomanian lower Frontier Formation in southwest Montana lie within or east of the fold and thrust belt in the Cretaceous foreland basin complex. Petrography of these strata record a complex interaction between source-area tectonism, basin subsidence, and sedimentation patterns associated with a cyclic sequence of transgressions and regressions. Because the petrographic data set was large (127 thin sections) and difficult to interpret subjectively, statistical techniques were used to establish sample and variable relationships. Theta-mode cluster and correspondence analysis were used to determine the contributing effect (total variance) of key framework grains. Monocrystalline quartz, plagioclase, potassium feldspar, and sandstone-, limestone-, and volcanic-lithic grain content contribute most to the variation in the framework-grain population. Theta-mode cluster and correspondence analysis were used to identify six petrofacies. Lower Blackleaf petrofacies (I-III) contain abundant monocrystalline quartz (55-90%) and sedimentary lithic grains (10-50%), which are distributed throughout the study area. Petrofacies I-III are differentiated by variable monocrystalline quartz and sedimentary lithic grain content. Upper Blackleaf and lower Frontier petrofacies (IV-VI) exhibit highly variable, sedimentary and volcanic lithic ratios, and contain less monocrystalline quartz (20-50%) than lower Blackleaf petrofacies. Information from quantitative analyses combined with available paleocurrent data indicates that Blackleafmore » and lower Frontier detritus was derived from variable source areas through time. Lower Blackleaf detritus was derived from Precambrian through Paleozoic sedimentary terranes to the west, north, and east; whereas, upper Blackleaf and lower Frontier detritus was derived from both sedimentary and volcanic terranes to the south.« less

Textural and Compositional Controls on Silica Diagenesis--A Case Study from Nugget Sandstone, Washakie Basin, Wyoming: ABSTRACT

Grain-size laminated quartzose sandstones (Q93F5R2) illustrate well-defined relations among framework grain size (GS), quartz type, silica cement (SC), and pressure solution (PS). The percentage of monocrystalline quartz grains with well-developed overgrowths (greater than 50% of grain not in contact with adjacent grains containing overgrowth) is related to grain size (71% coarse, 20% medium, 8% fine sand). Regardless of grain size, less than 10% of the polycrystalline quartz population exhibits well-developed overgrowths. For medium sand-size nonundulose, undulose, and polycrystalline quartz, the portion of grains with well-developed overgrowth is 29%, 8%, and 2%, respectively. All other factors being equal, first-cycle quartzose sandstones derived from metamorphic source rocks will lose porosity and permeability, due to silica cementation, at a slower rate than those sandstones (nonundulose quartz rich) derived from other sources. The silica cement present in the Nugget Sandstone is largely the result of pressure solution. Over the average grain size range of 0.22-0.35 mm, the volume represented by pressure solution can be depicted by the equation PS = -54(GS) + 26 (r = -0.85). SC = 99(GS) - 19 (r = +0.80) defines the relation between grain size and silica cement abundance. Sandstone intervals with an average grain size less than about 0.29 mm are characterized by an excess of silica, whereas for an average grain size above 0.29 mm the opposite is the case. Pressure-solution-produced silica mainly originated in finer grained units and migrated to coarser grained zones. When all grain sizes are considered, the volume of silica generated by pressure solution exceeds the amount of silica precipitated by overgrowth . End_of_Article - Last_Page 491------------

Granite Disintegration, Panola Mountain, Georgia

Biotite-induced disintegration of granite fragments in the soils of plant communities on the slopes of Panola Mountain proceeds rapidly during the early stages of plant succession. Complete disintegration of some fragments may take over 670 years. The grain size of the minerals in the plant community soils is strongly influenced by the size distributions of the minerals in the parent rock, taking into account fracturing of polycrystalline quartz into monocrystalline grains. The grain size distribution of these monocrystalline quartz grains is bimodal in the Panola granite and in the plant community soils during the later stages of plant succession.