Transparent Heavy Minerals Research Articles

OS MINERAIS PESADOS E IDADES DE ZIRCÕES DOS SEDIMENTOS DE PRAIAS (BARRAS EM PONTAL) DOS RIOS PURUS E ACRE NO ESTADO DO ACRE (BRASIL)

The Purus River and its largest tributary, the Acre River, originate in Peru and constitute the main drainage system for the northeast and southeast portions of the State of Acre. These rivers and their smaller tributaries develop their beds over the Solimões Formation (Miocene to Pliocene-Late) and form a broad dendritic drainage pattern. During the rainy season, due to the high rainfall in the region and the low resistance of the drained rocks, these rivers mobilize a large volume of sediment, which is deposited mainly during the dry season, forming beaches (pointed bars), predominantly composed of fine sand, silt and clay. To investigate the probable primary sources of these sediments and their possible geographic locations, a mineralogical and morphological study of their heavy minerals and a geochronological analysis of their detrital zircons were used. Heavy minerals were extracted from fractions between 0.062-0.125 and 0.125-0.250. The transparent ones were investigated using a petrographic microscope and the opaque non-magnetic ones, together with the lithic fragments using a Scanning Electron Microscope (SEM/SED). In descending order, the main transparent heavy minerals of the Purus River are epidote (19%), kyanite (17%), zircon (14.5%), andalusite (8%), tourmaline (7.4%) and sillimanite (5 .5%), in addition to these, in amounts less than 5%, staurolite, garnet, apatite, amphibole, chlorite, muscovite, biotite, anatase, pyroxene and cassiterite occur. With similar content and different proportions, the assemblage of heavy minerals from the Acre River consists of andalusite (22.5%), kyanite (22.5%), zircon (12%), epidote (8%), sillimanite (5%) and tourmaline (5%), its accessories are: garnet muscovite, chlorite, apatite, amphibole, biotite, staurolite, titanite, anatase, serpentine and rutile. The non-magnetic opaque minerals of both rivers were shown to be predominantly formed by ilmenite, and the ages obtained in the zircons varied from 180 Ma to 3000 Ma, with great frequency in the intervals between 200-400 Ma and 900-1200 Ma.

Mineralogy and Selenium Speciation Analysis of Early Cambrian Selenium-Rich Black Shale in Southern Shaanxi Province, China

Selenium (Se) is an essential trace element for humans and animals, and an excess of or deficiency in Se is harmful to health. Research on the selenium enrichment zone began in the late 1970s in Shuang’an, Ziyang, southern Shaanxi Province. Naore village is only one selenosis area in Shuang’an, Ziyang, China. Different scholars have conducted systematic studies on the occurrence of selenium, its organic geochemistry and biomarkers, and its content and enrichment patterns in this area. This study applied the TIMA (TESCAN integrated mineral analyzer) for the first time to conduct detailed mineralogical work. The minerals included quartz, carbonate minerals (calcite and dolomite), feldspar (plagioclase, albite, and orthoclase), biotite and muscovite, clay minerals (chlorite and kaolinite), hematite, pyrite, and accessory minerals (almandine, olivine, zircon, and apatite) in Naore village, Ziyang, Shaanxi Province. The ATi index (100 × apatite/(apatite + tourmaline)) is used to determine the source of heavy minerals and the degree of heavy minerals’ weathering. The content POS (100 × (pyroxene + olivine + spinel)/transparent heavy mineral) of olivine, pyroxene, and spinel in heavy minerals can reflect the contribution of basic and ultrabasic rocks in the source area. The ATi and POS indexes for the heavy minerals in the research area were 91.83~99.96 and 0.01~18.75, respectively, reflecting the abundance of volcanic rock material in their source. In addition, the migration, transformation, bioavailability, and toxicity of selenium in the environment are closely related to its species. The species of selenium in various selenium-rich areas (Naore, Wamiao, and Guanquan) mainly include unusable residues and organic forms, followed by humic-acid-bound selenium. The proportions of water-soluble, exchangeable, and carbonate-bound selenium are relatively small, and the proportion of Fe-Mn oxide-bound selenium is the lowest.

Provenance history of the eastern Pearl River Mouth Basin: Implications for the evolution of the South China margin

The provenance history of the Pearl River Mouth Basin is of great significance for understanding how the South China margin evolved from a Mesozoic Andean-type subduction margin into the present-day rifted passive margin. However, the long-term provenance history of continental margin basins in the northern South China Sea is poorly understood. Newly identified Mesozoic−Cenozoic successions from the Lufeng Sag in the eastern Pearl River Mouth Basin provide valuable records of the provenance history and related evolution of the South China margin. Here, we trace the provenance of the eastern Pearl River Mouth Basin using U-Pb ages of zircon and ZTR values (proportions of zircon, tourmaline, and rutile in all transparent heavy minerals) of heavy minerals, and determine the tectonic setting and crustal thickness using trace element ratios and Eu anomalies in zircon. The results show that from the middle Eocene strata—which have a U-Pb age spectrum similar to strata of the Upper Cretaceous—to the Miocene strata, the proportion of Mesozoic age populations gradually increases, while the proportion of Paleozoic age populations decreases. In addition, following the middle Eocene high values, the ZTR values decreased during the late Eocene and then increased during the early Oligocene. Based on the variations in zircon age populations and ZTR values, the middle Eocene sediment is interpreted to have been recycled from Upper Cretaceous to middle Eocene successions, followed by an early Oligocene provenance change from intrabasinal to extrabasinal sources. Moreover, the zircon trace element ratios and Eu anomalies indicate that a widespread Mesozoic continental magmatic arc formed before ca. 90 Ma along the South China margin, and the crust simultaneously thickened during this time. In accordance with the provenance history, the evolution of the South China margin is divided into three tectonic phases: the Paleo-Pacific, Proto-South China Sea, and South China Sea. During the transition from the Paleo-Pacific to the Proto-South China Sea tectonic phase, sediment was recycled from Upper Cretaceous to middle Eocene successions in the eastern Pearl River Mouth Basin. During the transition from the Proto-South China Sea to the South China Sea tectonic phases, the provenance changed from intrabasinal to extrabasinal sources.

Mechanical transport revealed by optical textures of heavy minerals in aeolian sand: A case study in the Badain Jaran Desert, Northwestern China

Determining whether and to what extent the relative abundance of heavy minerals in original detrital assemblage has been modified by mechanical transport is beneficial for understanding regional historical climate changes and acquiring modern sediment provenance information. Utilizing the frequency of surface mechanical optical textures of heavy minerals may be an effective approach to address this question. However, the connection between the frequency surface mechanical optical textures of heavy minerals and the variations in the relative abundance of these minerals remains uncertain. In this study, 12 modern aeolian sand samples were collected from the Badain Jaran Desert in hyper arid region of northwestern China, characterized by weak weathering to analyze their relative contents of five major heavy minerals. Then, 3796 transparent heavy mineral grains were photographed under the parallel light of a polarizing microscope, and the frequency of 13 surface mechanical optical textures were calculated. The results reveal that the variations in the relative abundance of heavy minerals are substantially influenced by mechanical transport. The decrease in the relative abundance of heavy minerals with weak mechanical stability primarily attributed to mechanical collision. Conversely, the variations in the relative abundance of heavy minerals with strong mechanical stability are primarily influenced by mechanical abrasion. Therefore, mechanical transport impact on the relative abundance of heavy minerals in regions with weak chemical weathering. Establishing heavy mineral characteristic indices for provenance studies using the relative abundance of mechanically unstable minerals may not directly indicate transport distance but rather the strength of wind forces, which have significant potential in palaeo wind regime studies. This study expands the research field of sediment surface micromorphology and has potential applications in inferring past climate changes and determining modern sediment provenance.

Provenance and Origin of the Sand Dunes Sediments in the Na’ama Area / Southeast Tikrit City Northern Iraq

Study of three Barchan sand dunes in Na'ama area southeast Tikrit city have been carried out for (10) samples, the investigation included petrographical, mineralogical and geochemical aspects of the sand dunes from grain size point, the sand grains are commonly sub-rounded to sub-angular forming about (98.8%) with (1.2%) of mud. Petrographically, the sand are sub-litharenite to lithic arenite and mineralogical analysis indicated that most of sand dunes are mainly consist of quartz and carbonate rock fragments in addition to rare feldspar and mica where quartz prevail the mineralogy of all sand dunes due to the selective wind sorting which concentrates more quartz grains, and to the aeolian weathering activity which has depleted the feldspar grains through subaerial collisions. Fine grained mean grain size, very well to moderately sorted, near symmetrical skewness with leptokurtic distribution are characterized the sand dunes in the study area. These statistical parameters show that the sand dunes are extremely controlled by sedimentary sources (Injana Formation sediments). Also, the rarities of organic materials within the sand dunes indicate to the rarity of coverage plant within the seasonably moved sand dunes.
 Several transparent heavy minerals are identified in the sand dunes such as Tourmaline, Hornblende, Olivine, Chlorite, Ankerite and Zircon with well rounded edges due to the transportation, in addition to opaque heavy minerals of iron oxide like Magnetite, Hematite and Chromite concentrated within sand fraction. Atomic absorption analysis distinguished many types of major and trace elements in the sand dunes too. These heavy minerals and trace elements refer to that the sand dunes were derived from ancient igneous and metamorphic rocks which eroded and deposited later within Injana Formation

No major temporal provenance variation on the Chinese Loess Plateau since the late Miocene — insight from stable heavy mineral ratios

Heavy mineral assemblages have been demonstrated effective in tracking the dust provenance younger than 500 ka on the Chinese Loess Plateau (CLP). However, prior to 500 ka, diagenetic alternation has proven to affect the validity of heavy mineral assemblage in indicating loess provenance. In order to circumvent this caveat, here we use several previously-proposed ratios of stable heavy minerals to study the dust provenance on the CLP since the late Miocene. These provenance tracers reveal that dust on the CLP is dominantly sourced from the Northeastern Tibetan Plateau with some input from the North China Craton, without significant changes across the late Miocene-Pliocene to Pliocene-Quaternary boundaries. This result is different from previous results based on Sr, Pb isotopes, and transparent heavy mineral composition, but is consistent with Nd and Hf isotopes and detrital zircon U-Pb age results. We argue that the changes based on Sr, Pb isotopes, and heavy mineral assemblages are caused by factors other than provenance changes. We conclude that the CLP has been sourcing dominantly from the Northeastern Tibetan Plateau since the late Miocene and formation of the CLP is genetically linked with existence of a high plateau near its western margin.

Tracing erosion patterns in South Tibet: Balancing sediment supply to the Yarlung Tsangpo from the Himalaya versus Lhasa Block

AbstractThe Yarlung Tsangpo, draining the Himalayan‐Tibetan orogen along the Indus‐Yarlung suture zone, receives detritus from the deformed remnants of both Indian margin to the south and Asian margin to the north. High resolution petrographic, heavy‐mineral and geochemical datasets, combined with published geochronological data, allow us to monitor compositional changes, estimate erosion rates and investigate lithologic, climatic and anthropic controls on sediment fluxes along this large sediment‐routing system entirely developed within high mountain areas. Sediment generated from the Lhasa Block along the southern margin of Asia is characterized by abundant feldspar and volcanic rock fragments, amphibole‐dominated transparent heavy mineral suite and high concentrations of K, Rb, Be, Th and Pb. Himalayan‐derived sand, instead, is characterized by sedimentary to low‐rank metasedimentary rock fragments, poor transparent heavy mineral suite dominated by durable recycled (zircon, tourmaline) or metamorphic minerals (chloritoid, garnet) and high Ca concentration. Sand from the ophiolitic suture is distinguished by serpentinite grains and mafic volcanic or metavolcanic detritus, transparent heavy mineral suite including olivine, Cr‐spinel, enstatite and clinopyroxene, and high Mg, Cr, Ni and low rare earth elements. Himalayan detritus is prominent in Yarlung Tsangpo upper reaches, whereas detritus from the Lhasa Block becomes progressively predominant in the middle and lower reaches. Provenance budgets based on integrated petrographic, heavy‐mineral and geochemical datasets indicate that ca. 83% of the detritus is supplied by the Lhasa Block and the rest mostly from the Himalaya (ca. 12%) and subordinately from the ophiolitic suture (5%). A low average erosion rate of ca. 0.06 mm/a was estimated for the Yarlung Tsangpo catchment upstream of the Namche Barwa syntaxis, which resulted from dry climate, relatively mild average relief and sediment storage in wide valley tracts of the middle and lower reaches. The decrease in sediment flux recorded in recent decades is mainly ascribed to growing human activities, which are becoming a prominent control on sediment generation and transportation even in the high‐mountain area of South Tibet.

Multi-Proxy Provenance Analyses of the Kingriali and Datta Formations (Triassic–Jurassic Transition): Evidence for Westward Extension of the Neo-Tethys Passive Margin from the Salt Range (Pakistan)

The Salt Range, in Pakistan, preserves an insightful sedimentary record of passive margin dynamics along the NW margin of the Indian Plate during the Mesozoic. This study develops provenance analyses of the Upper Triassic (Kingriali Formation) to Lower Jurassic (Datta Formation) siliciclastics from the Salt and Trans Indus ranges based on outcrop analysis, petrography, bulk sediment elemental geochemistry, and heavy-mineral data. The sandstones are texturally and compositionally mature quartz arenites and the conglomerates are quartz rich oligomictic conglomerates. Geochemical proxies support sediment derivation from acidic sources and deposition under a passive margin setting. The transparent heavy mineral suite consists of zircon, tourmaline, and rutile (ZTR) with minor staurolite in the Triassic strata that diminishes in the Jurassic strata. Together, these data indicate that the sediments were supplied by erosion of the older siliciclastics of the eastern Salt Range and adjoining areas of the Indian Plate. The proportion of recycled component exceeds the previous literature estimates for direct sediment derivation from the Indian Shield. A possible increase in detritus supply from the Salt Range itself indicates notably different conditions of sediment generation, during the Triassic–Jurassic transition. The present results suggest that, during the Triassic–Jurassic transition in the Salt Range, direct sediment supply from the Indian Shield was probably reduced and the Triassic and older siliciclastics were exhumed on an elevated passive margin and reworked by a locally established fluvio-deltaic system. The sediment transport had a north-northwestward trend parallel to the northwestern Tethyan margin of the Indian Plate and normal to its opening axis. During the Late Triassic, hot and arid hot-house palaeoclimate prevailed in the area that gave way to a hot and humid greenhouse palaeoclimate across the Triassic–Jurassic Boundary. Sedimentological similarity between the Salt Range succession and the Neo-Tethyan succession exposed to the east on the northern Indian passive Neo-Tethyan margin suggests a possible westward extension of this margin.

A Comparative Heavy Mineral Study of the Cenozoic Sediments of Assam and Siwalik Foreland Basins, Northeast Himalaya

Heavy mineral assemblages of sedimentary units are used as an essential provenance constraint. The sedimentary successions of the southern Assam and Siwalik foreland basins were analyzed for their heavy mineral suits and provenance determination. Heavy minerals were identified using the petrological microscope, X-ray Diffraction (XRD) and Electron Probe Micro Analyzer (EPMA) analyses. The study demonstrates that heavy minerals weight percentage in the southern Assam basin is lower than that of the northeast (NE) Siwalik basin. In the Assam basin, the weight percentage of dense minerals varies from 0.08% to 1.31%; however, in the Siwalik sediments, it varies from 2.27% to 5.78%. The relative dominance of opaque minerals over transparent heavy minerals is observed throughout the Cenozoic rocks of Assam basin, except for the Tipam unit. At the same time, the Siwalik basin successions show a low percentage of opaque minerals and high amount of non-opaque heavies. Detritus in the Assam basin reveals a distinct change in the occurrence of heavy mineral assemblages (amphibole, aluminosilicates, staurolite and a high percentage of epidote, pyroxene and sphene) in the Mio-Pliocene unit (Tipam sandstone) compared to Barail and Surma older units, implying involvement of an additional orogenic source. This study suggests that NE Siwalik sediments were primarily derived from Himalayan rocks of the Siang window, while heavies in the detritus of the southern Assam basin exhibits a mixed provenance both from the eastern Himalaya, chiefly from Dibang and Lohit valley and Indo-Burman-Ranges (IBR).

Provenance and tectonic setting of Paleogene sandstone in the center of the northern Qaidam Basin, China

The average thickness of Paleogene sandstones reaches about 3000 m or even 4000 m at the northern margin of the Qaidam Basin. However, the provenance of these sandstones has been uncertain; thus, more comprehensive research is needed. Integrated research was conducted on the provenance based on petrological characteristics, heavy mineral analysis, and U–Pb dating in the center of the northern Qaidam Basin. The results of lithofacies analysis show that the Paleogene sandstones were mainly derived from an active continental magmatic arc, subduction-accretionary or fold-thrust belt; The results of heavy mineral analysis show that the heavy mineral combinations in the Lenghu seventh area and Mabei area are consistent, mainly composed of zircon, garnet, magnetite, and leucosphenite. Moreover, GZi [garnet/garnet + zircon] and RZi [leucosphenite/(leucosphenite + zircon)] have good correlation with ZTR (the ZRT index refers to the proportions of three kinds of transparent heavy minerals in clastic rocks: zircon, rutile, and tourmaline). The zircon U–Pb results for the Paleogene sandstone in the northern Mabei area are consistent with the results of U–Pb dating in the middle of the South Qilian Mountains, which yielded the same results as river sand in the modern Yuka River. Based on three types of data, it is confirmed that the two areas, Lenghu seventh and Mabei, had the same sediment sources in the Paleogene, mainly from the middle of the South Qilian Mountains. The source rocks are mainly neutral - basic magmatic rocks and metamorphic rocks and the structure background is dominated by the magmatic island arc and the collision-thrust suture zone at the active continental margin.

Selective sediment transport during Hurricane Sandy on Fire Island (New York, USA): Inferences from heavy-mineral assemblages

ABSTRACT In October 2012, Hurricane Sandy caused severe erosion on beaches and dunes of Fire Island (New York, USA). Major shoreline changes occurred with erosional dominance in the upper shoreline and aggradation in the lowermost section of the beach due to the deposition of eroded upper-beach and dune sediment. Sand laminae with a high concentration of heavy minerals (“black sand laminae”) were observed in three excavated trenches located on a washover terrace and fan on the east side of Fire Island. The mineral composition of these laminae reveals the presence of high quantities of magnetite, ilmenite (as opaque minerals), and garnet (as the main translucent mineral). These heavy-mineral-enriched laminae were formed as waves eroded and transported sand from the primary dune and smaller relict dunes under specific hydrodynamic conditions that promoted grain sorting according to differences in size and specific gravity. Based on the concentrations of certain heavy minerals, the threshold for primarily density-driven sorting probably lies between the specific gravity of less dense opaque mineral (ilmenite, 4.7) and almandine (4.3), the most common transparent heavy mineral. The number of laminae and concentrations of heavy minerals vary between trenches on the overwash terrace and appear to be controlled by their distance from sediment sources. The trench with the greatest number of laminae and higher heavy-mineral concentrations is located farthest from the main dune but is just 10 m inland of a relict dune that acts as the primary source of sediment of the washover deposit in this trench. A conceptual model for deposition of heavy-mineral layers is presented based on geomorphological and sedimentological evidence allowing the definition of a density threshold.

Mineralogy of Sand Fraction in Selective Soil Sections in Baghdad City

This study has been undertaken to investigate the mineralogical properties and morphological features of sand fraction in some soils of Baghdad / Iraq.The morphological features of sand fractions were studied by Polarized optical microscope. Results have shown that the grains of these minerals from samples of sands have different colors, those from the surface horizons have dark brownish spots, due to staining by organic matter, and have a yellowish– to yellowish brown spots due to accumulation of Iron oxides.Results of light minerals indicated that quartz is dominant due to effect of parent material of these soils. Two types of opaque minerals (black and brown) are found, whereas the brown opaque minerals were obvious in heavy minerals.Three groups of transparent heavy minerals are found, stable minerals (Pyroxen and Amphibole), metastable minerals (Epidote and Garnet), and Ultra stable minerals (Zircon and Tourmaline).

The Chemical Composition and Surface Texture of Transparent Heavy Minerals from Core LQ24 in the Changjiang Delta

The assessment of textural and compositional modifications of detrital sediments is required to reconstruct past source to sink dynamics. The Changjiang Delta is an ideal location to study the sedimentary environment from the Pliocene to Quaternary transition. In the present study, we aim to decipher the response of heavy minerals to mechanical wear and chemical weathering since the Pliocene. With the application of a scanning electron microscope and an electron probe, the geochemistry and surface texture of different heavy minerals (amphibole, epidote, and tourmaline groups) with grain-size fractions of 32–63 µm and 63–125 µm were studied. The result shows that the surface texture of unstable minerals (amphibole, epidote) changed under strong chemical weathering in the Pliocene sediments. By contrast, unstable minerals of the Pleistocene sediments are relatively fresh and similar to those of the modern Changjiang sediment. The stable mineral tourmaline does not exhibit morphology changes in different chemical weathering conditions. No effect of grain size on geochemical composition is noticed. The single minerals of very fine sand and coarse silt show similar geochemical and morphological features. The integration of mineralogy, geochemical data, and grain size parameters yield a more precise understanding of the physical and chemical response of heavy minerals to different weathering conditions. The outcome of the study is also helpful in deciphering sediment provenance changes and environmental changes in the Changjiang basin.

Provenance of Heavy Minerals: A Case Study from the WNW Portuguese Continental Margin

This work describes and interprets the presence of heavy minerals in the WNW Portuguese continental margin using a set of 78 bottom samples collected from three distinct areas of this margin: the Porto, Aveiro, and Nazaré canyon head areas. The main transparent heavy mineral assemblage (mineral grains with frequencies ≥1% identified under a petrographic microscope) is composed of amphibole, andalusite, tourmaline, biotite, garnet, staurolite, pyroxene, zircon, and apatite. The felsic igneous and metamorphic rock outcrops in the main Northern Portuguese river basins and the relict sedimentary continental shelf deposits explained the presence of most of these mineral grains (both considered as distal sources). However, the presence of pargasite, augite, diopside-hedenbergite, enstatite-ferrosilite, and forsterite in the Porto and Aveiro areas (minerals identified by electronic microprobe analysis) is probably related to the presence of an igneous basic source next to dolomitic limestones affected by thermal metamorphism. These geological formations are considered as local sources. The high concentration of biotite observed in the Nazaré area is the result of the selective transport of the most lamellar sand particles of this mineral.

Transparent heavy minerals and magnetite geochemical composition of the Yangtze River sediments: Implication for provenance evolution of the Yangtze Delta

Heavy mineral and detrital magnetite geochemistry were analyzed to extract sediment provenance indexes from different reaches of the modern Yangtze River which were used to trace sediment source of the Yangtze Delta and to speculate its geomorphology change since the Pliocene. Our results show that diagnostic heavy minerals of the upper Yangtze sediment are characterized by clinopyroxene (12% on average) and magnetite (7% on average); the middle reaches by ilmenite, zircon and tourmaline; and the local small rivers by fluorite. Detrital magnetite composition of Ti, Mg, V and Cr is high in the upper Yangtze from the underlying basalt. These diagnostic indexes are then used in the Pliocene sediment core to extract provenance signal of different Yangtze reaches. Analysis of core sediment of the Yangtze Delta reveals that sediment provenance of the Pliocene was from local small rivers. Since the beginning of the Pleistocene, core sediments provenance was similar to that of the middle Yangtze tributaries. After 1.2Ma, high content of pyroxene and magnetite grains that are rich in Ti, Mg, V, Cr imply sediment provenance signals from the upper Yangtze. Sediment provenance shift from short-distance sources to more distant sources indicates that the geomorphology of the Yangtze Delta region has undergone a great transformation since the Pliocene. This dramatic landform change is likely in response to continuous uplift of the Tibetan plateau and accelerated subsidence of the east China coast since the Pliocene.

Heavy mineral compositions and zircon U-Pb ages of Cenozoic sandstones in the SW Qaidam basin, northern Tibetan Plateau: Implications for provenance and tectonic setting

The Qaidam basin is the largest intermountain basin within the Tibetan Plateau. The spatio-temporal evolution of the basin and the provenances of the deposits in the SW Qaidam basin were greatly influenced by the boundary ranges. Comprehensive research is needed to identify the relationships between the basin and the surrounding ranges. Therefore, 4682 heavy mineral data from 70 wells and 720 detrital zircon ages from 8 samples were used to investigate the provenances of the deposits in the SW Qaidam basin and to further constrain the tectonic evolution of the boundary ranges. The heavy mineral data, zircon U-Pb ages, and paleocurrent data indicate that the Qimen Tagh Range and the Altyn Tagh Range were two provenances of the sediments deposited in the SW Qaidam basin during the Cenozoic. The variations of heavy mineral assemblages and ZTR index (100∗(zircon+tourmaline+rutile)/total transparent heavy minerals) on the northern flank of the Qimen Tagh Range suggest that the Qimen Tagh Range experienced rapid uplift in the Early to Middle Miocene. Furthermore, according to the greatly increased quantities of epidote and hornblende sourced from the Altyn Tagh Range and the obvious decrease in the ZTR index values, the Altyn Tagh Range underwent fast uplift in the Late Oligocene to Early Miocene. In addition, based on the ages of the granitic plutons in the Altyn Tagh Range and the zircon ages in the Ganchaigou and Qigequan sections, the strike-slip movement of the Altyn Tagh Fault (ATF) initiated during or no later than the Middle Eocene, resulting in the ATF offsets of ca. 200km between the Middle Eocene and the Miocene and of ca. 345km between the Middle Eocene and the present.

Provenance of bar-top Sediments at Tons River near Allahabad

ABSTRACT The bar-top sediments at the Tons river deposited mainly from the suspension current during waning stage condition of river are collected to study their provenance on the basis of clay mineralogy, heavy minerals and magnetic properties. The clay mineral assemblages in samples predominantly consist of illite, with minor amounts of kaolinite, smectite and chlorite. The clay minerals are contributed due to (i) weathering and decomposition of shales, argillaceous limestones and pyroclastic deposits of upper Vindhyan Groups and (ii) weathering and erosion of Banda plain of Gangetic alluvium. The low ZTR index for the studied samples indicates poor sediment maturity, rapid erosion in the source region and short transportation of detritus. The transparent heavy mineral assemblages in the sediment samples predominantly consist of garnet, with minor amounts of tourmaline, zircon, hornblende, enstatite, hypersthene, rutile, tremolite, kyanite, sillimanite, andalusite, chlorite, epidote, wollastonite, and staurolite. The heavy minerals are dominantly angular to sub-angular with some rounded to sub-rounded grains. The rounded grains indicate multicyclicity and derivation from Vindhyan sandstones. The angular grains are either contributed due to erosion of primary rocks of Bundelkhand gneissic complex and or various Gangetic alluviums. The magnetic properties from sediment samples indicate that the antiferro-magnetic minerals (illite, chlorite and smectite) are more concentrated in clay sized particles and it also indicated mixed source rocks for the bar-top sediment of Tons river.

Heavy mineral concentrations in the sandstones of Amij Formation with particular emphasis on the mineral chemistry and petrographic characteristics of monazite, western desert of Iraq

The heavy minerals in the clastic unit of the Lower Jurassic Amij Formation exposed in the western desert of Iraq were studied. The uppermost part of the clastic unit contains thin, placer-like black sandstone horizons that are radioactive and abnormally rich in heavy minerals (0.6–56%), dominated by opaque (65%) and transparent (35%) heavy minerals. The minerals, in the order of decreasing abundance are pseudorutile, goethite, zircon, hematite, magnetite, monazite, rutile, leucoxene, tourmaline, ilmenite, chromite, and few others. Electron probe microanalysis (EPMA), microscopic and autoradiographic observations and analysis showed that the monazite is monazite-(Ce) type with an average composition of (Ce0.39Nd0.16La0.19Pr0.04Sm0.02Gd0.02Eu0.01Y0·04Th0·06U0·01Ca0·05Fe0.01)(P0·98Si0.03)O4.Monazite consists predominantly of REE-oxides (57.93%) and P2O5 (29.31%), with minor amounts of ThO2 (6.60%), Y2O3 (1.92%), UO2 (0.76%), CaO (1.14%), SiO2 (0.69%), and FeOt (0.17%). The dominant compositional substitution operating between REE and P were a mixture of the complex cheralite type substitution ([REE]−2 [Th][Ca]) and the coupled huttonite type substitution ([REE]−1 [P]−1 [Th][Si]). The chondrite-normalized REE distribution patterns of monazite show enrichment in LREE with positive Eu- and Pr-anomalies of 1.46 and 9.13, respectively. The median values of (La/Sm)CN and (La/Nd)CN ratios are 4.35 and 1.97, respectively. Zircon which is the dominant transparent mineral is Hf-rich that is composed of 30.61% SiO2, 57.58% ZrO2, 7.03% HfO2, 2.04% Y2O3, 0.56% ThO2, 0.19% UO2, and 0.19% Al2O3 corresponding to a formula (Zr0.909Hf0.065Th0·004U0·001Y0.031)Σ1.011(Si3·966Al0.028)Σ0.999O4. Rutile and tourmaline form 7% and 4% of the heavy minerals. Ilmenite which is one of the predominant heavy minerals forms 2.5% of the opaques because it is pervasively altered to Ti-Fe oxides. In addition of zircon and monazite, the chemical compositions of most of the other heavy minerals are also given in this study. The expected dominant source of heavy minerals and their host sandstones are most probably the felsic igneous and metamorphic complexes of the Arabian Shield, currently located ∼600 kms to the south of the studied area. The heavy minerals were carried from the source area by northward moving rivers and sorted out by ocean waves as black sand concentrations at the delta mouth along the southern beaches of the Neo-Tethys Ocean under passive margin tectonic setting. This border was apparently bordering the current western part of Iraq during Upper Jurassic period.

Provenance of sandstone on the western flank of Anambra Basin, Southwestern Nigeria

Petrographic and heavy mineral studies were carried out on clastic deposits that crop out in Ikpeshi, Auchi and Fugar localities in order to determine the provenance of the sediments and the tectonic setting of the source area. The localities are in the western flank of the Anambra basin, southwestern Nigeria. Petrographic study shows that the sandstone deposits are composed of variable amounts of quartz, feldspars and lithic fragments with minor occurrence of authigenic silica and chlorite cements. Quartz is the predominant detrital mineral in all the samples accounting for over 87 % of the total framework composition. The representative samples from all the localities contain 88-94 % quartz, 1-8 % lithic fragment, 1-4 % cement and 0-4 % matrix. Feldspar is present in small amount only in samples from Fugar locality. The sandstones each classify as quartz arenites and sublitharenites. Both opaque and transparent heavy minerals occur in the sandstones. The opaques are magnetite, ilmenite and leucoxene. Together, they account for 35 – 55 % of the total heavy mineral abundance. The transparent heavy minerals are zircon, tourmaline, rutile, staurolite, and apatite listed in order of decreasing abundance. The heavy mineral assemblages in the localities are similar except for the absence of rutile from the sediments of Ikpeshi locality. The heavy mineral grains are subangular to rounded. The zircon-tourmaline-rutile (ZTR) index for the sediments from the three localities are generally high and range from 90.5 to 100% indicating high degree of mineralogical maturity of the sandstones. The heavy mineral suites and the petrographic signatures of the sandstones suggest derivation mainly from acid igneous rocks, gneisses and older sandstones in both stable tectonic and recycled orogenic settings. However, the absence of rutile in sandstone from Ikpeshi may suggest derivation from lithologically more restricted provenance.

Heavy mineral assemblages of the Storegga tsunami deposit

This study applies heavy mineral analysis to the Storegga tsunami deposit across a range of locations (Whale Firth, Maggie's Kettle Loch and Scatsta Voe) in Shetland (Scotland). The usefulness of this proxy is tested in the identification and characterization of these palaeotsunami units. Furthermore, provenance relationships are established based on the mineralogical content of tsunami deposits and their potential source. Finally, the capability of identifying different phases of tsunami inundation in an 8200years old tsunami deposit is attempted.Our results show that, overall, tsunamigenic samples presented a clear dominance of garnets and amphiboles. While Whale Firth presented a more balanced distribution between these two mineral groups, in Maggie's Kettle Loch and Scatsta Voe the tsunamigenic samples are dominated by amphiboles (>90% of transparent heavy minerals).Focusing on the two dominant heavy minerals (garnets and amphiboles) and their vertical variation, one could observe that garnets mimic the heavy mineral concentration variability — higher values at the base and decreasing values to the top. This effect of concentration of the heaviest of the heavy minerals assemblage presents similarities with the formation of beach placer deposits. In fact, based on the heavy mineral vertical variation of the tsunami deposits in Maggie's Kettle Loch, Scatsta Voe and Whale Firth it is possible to conclude that hornblende (most likely amphibole of the assemblage) has the lowest concentration factor indicating that its transport process is more efficient and consequently most of its particles eventually may have moved offshore in the backwash phase of the tsunami. Furthermore, the more platy shape of amphiboles also favours a slower deposition. The opposite can be observed for garnets, which require more energy to be transported (i.e. they are more difficult to entrain by the tsunami waves) and tend to be more easily preserved in the formation of a tsunamigenic (placer) deposit.The work presented here is of particular relevance for future high resolution sedimentological studies aiming to distinguish different inundation phases of the Storegga tsunami, and assess the degree of preservation of these deposits, especially considering the specific geomorphological and stratigraphic depositional setting of Scotland.