Heavy Mineral Provenance Research Articles

Heavy mineral provenance and paleomagnetic studies of Mesozoic rocks in the Gold Beach terrane, southwestern Oregon, USA

Heavy mineral provenance and paleomagnetic studies of Mesozoic rocks in the Gold Beach terrane, southwestern Oregon, USA

Distribution and provenance of heavy minerals from recent sediments of Green Lake, North Brazil, revisited

Geostatistical and multivariate statistical analyses were applied to heavy mineral data from an Amazonian fluvial-lake system near the Tapajós River mouth to investigate the spatial distribution and source-area of sediments. Twenty-one points were investigated, and the physical characteristics of the Green Lake deepest point were determined. Sand accumulates in the lake margins and mud quantity increases towards the lake center. Heavy mineral assemblage is composed of zircon, tourmaline, kyanite, rutile, staurolite, anatase, sillimanite, garnet, and spinel. Tourmaline, staurolite, and spinel are more abundant in the southeast area of the lake, while kyanite is dominant in the north area and zircon is in the whole lake except in its southeast area. Zircon - tourmaline and zircon - staurolite pairs are negatively correlated (r= -0.947 and -0.775, respectively), while tourmaline - staurolite and sillimanite - anatase pairs have a positive correlation (r= 0.628 and 0.675, respectively) which indicate different source rock types. Geostatistical analysis grouped the heavy minerals in three grups: Group 1 (tourmaline – staurolite – spinel - kyanite) and Group 2 (garnet – rutile – sillimanite - anatase) related to metamorphic source rocks ranging from medium to high grade, and Group 3 (zircon) related to acid igneous source rocks. The heavy mineral assemblage of Green Lake is analogous to the assemblage of the Alter do Chão Formation, indicating that this formation is the source of sediments of Green Lake.

Interplay of Multiple Sediment Routing Systems Revealed by Combined Sandstone Petrography and Heavy Mineral Analysis (HMA) in the South Pyrenean Foreland Basin

Combined sandstone petrography and heavy mineral analysis allow to decipher different sediment routing systems that could not be resolved by one method alone in the South Pyrenean foreland basin. We apply this approach to deltaic and alluvial deposits of the southern part of the Jaca basin, and in the time equivalent systems of the nearby Ainsa and Ebro basins, in order to unravel the evolution of source areas and the fluvial drainage from the Eocene to the Miocene. Our study allows the identification of four petrofacies and five heavy-mineral suites, which evidence the interplay of distinct routing systems, controlled by the emergence of tectonic structures. Two distinct axially-fed systems from the east coexisted in the fluvial Campodarbe Formation of the southern Jaca basin that were progressively replaced from east to west by transverse-fed systems sourced from northern source areas. In the late stages of evolution, the Ebro autochthonous basin and the Jaca piggy-back basin received detritus from source areas directly north of the basin from the Axial Zone and from the Basque Pyrenees. Coupling sandstone petrography with heavy mineral provenance analysis allows challenging the existing model of the South Pyrenean sediment dispersal, highlighting the relevance of this approach in source-to-sink studies.

Provenance of heavy minerals to the Middle and Upper Jurassic epicontinental deposits of NW Poland

The source of clastic material supplied to the epicontinental sea during the Middle and Late Jurassic in the Pomeranian Segment of the northern part of the Mid-Polish Trough is analysed, using deposits from the Rzeczyn PIG-1 borehole that represent the Łyna, Chociwel, Brda, Pałuki, Kcynia and Rogoźno formations. Heavy mineral analysis, including weathering indices (ZTR, GZI, RZI and Q) and standardised scores for each mineral species, shows that each formation is characterized by a different heavy minerals association. In each association, transparent minerals include both ultrastable minerals (zircon, tourmaline and rutile), occurring in various proportions, and unstable minerals. This indicates that deposits subject to earlier multiple reworking were eroded from the surrounding landmasses. Most probably these deposits represented Triassic rocks, although fresh weathering covers were also eroded. The main direction of clastic material supply was from the N and NW, and to a lesser degree from the NE. The main reasons for changes in the source areas were probably sea level oscillations, while during regressions, exposed parts of the seabed became source areas of clastic material. Conversely, during transgressions, parts of the seabed became cut off from the supply of clastic material from eroded landmasses.

Deciphering the Late Paleozoic to Mesozoic tectono sedimentary evolution of the northern Bohemian Massif from detrital zircon geochronology and heavy mineral provenance

From Permian to Late Cretaceous, the northern Bohemian Massif experienced a complex intra-plate tectono sedimentary evolution involving development of at least four generations of sedimentary basins in different settings. We examine this protracted evolution using stratigraphic changes in sediment provenance, analyzed through heavy mineral assemblages and U–Pb detrital zircon geochronology (by laser-ablation ICP–MS) in Permian, Jurassic, and Late Cretaceous successions. The provenance data point to multiple, temporally evolving sources ranging from local (e.g., the ʽWest Sudetic Islandʼ) through more distant from elsewhere in the Bohemian Massif to exotic, likely derived from Baltica. The latter is interpreted as a trace of now completely eroded Late Jurassic to Early Cretaceous basin that once covered the Lusatian (Lausitz) Block and received the Baltica-derived detritus from northerly fluvial and deltaic depositional systems. We suggest that fill of this basin was recycled into the Bohemian Cretaceous Basin during progressive unroofing of the West Sudetic Island. A time-slice reconstruction of the paleogeographic and tectono sedimentary evolution of the northern Bohemian Massif is then developed to show that periods of basin development and deposition (early Permian, late early Permian to Early Triassic, Middle Jurassic–Early Cretaceous, and Late Cretaceous) were interrupted by major depositional gaps (Middle Triassic–Early Jurassic, mid-Cretaceous, and post-early Campanian). The Mesozoic depositional episodes resulted from reactivation of major NW–SE strike-slip fault zones due to stress transfer from the North Atlantic Rift during Jurassic to Early Cretaceous, overridden by the far-field effect of convergence of Iberia, Africa, and Europe during Late Cretaceous.

Competing sediment sources during Paleozoic closure of the Marathon-Ouachita remnant ocean basin

AbstractThe Paleozoic construction of Pangea advanced southwestward from the Appalachian system to the Marathon fold-and-thrust belt in west Texas and progressively closed a remnant ocean basin between Laurentia and Gondwana. The resulting collisional orogen was a potential driver of Ancestral Rocky Mountain tectonism and impacted continental-scale sediment routing. New detrital zircon U-Pb geochronologic and heavy mineral provenance data from Ordovician–Pennsylvanian strata in the Marathon fold-and-thrust belt, and Permian strata in the Guadalupe Mountains of west Texas record changes in sediment provenance during the tectonic development of southwestern Laurentia and the Delaware Basin. In the Marathon fold-and-thrust belt, Ordovician rocks (Woods Hollow and Marathon Formations) record peri-Gondwanan sediment sources prior to continent collision. Syncollisional Mississippian and Pennsylvanian rocks (Tesnus, Haymond, Gaptank Formations) record contributions from distal Appalachian sources, recycled material from the active continental suture, and volcanic arc material from Gondwana. Near the Guadalupe Mountains, postcollisional Permian strata (Delaware Mountain Group) from the northern Delaware Basin margin suggest a dominantly southern catchment that was sourced from the deforming suture and Gondwanan arc. The results demonstrate that both plates and the active suture zone were sources for the siliciclastic wedge, but their proportions differed through time. These results also suggest that the delay between initial late Mississippian suturing in the Marathon region and increased mid-Permian siliciclastic deposition into the northern Delaware Basin may have been linked to a southward catchment expansion that integrated the collisional belt and southern volcanic arc into a broadly north-directed sediment dispersal system.

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.

Provenance of Heavy Minerals for the Quaternary Coastal Plain of Southernmost Brazil (Rio Grande do Sul State)

Carassai, J.J.; Lavina, E.L.C; Chemale, F., Jr., and Girelli, T.J., 2019. Provenance of heavy minerals for the Quaternary coastal plain of southernmost Brazil (Rio Grande do Sul State). Journal of Coastal Research, 35(2), 295–304. Coconut Creek (Florida), ISSN 0749-0208.During the Quaternary, an extensive barrier system was developed in southern Brazil and northern Uruguay. The patterns of variation in the distribution and behavior of heavy minerals present in the aeolian and marine (upper shoreface-foreshore) facies of the four barriers formed in the Rio Grande do Sul costal plain were identified. Minerals were analyzed by scanning electron microscopy, including epidote, tourmaline, zircon, magnetite/ilmenite, polymorphs of aluminum silicates (andalusite, kyanite, and sillimanite), staurolite, rutile, amphibole, pyroxene, corundum, perovskite, chromite, garnet, apatite, monazite, xenotime, spinel, and titanite. In all of the barriers, zircon, magnetite, and ilmenite are the most important, followed by chromite, garnet, rutile, tourmaline, staurolite, and epidote. In total, heavy minerals indicate two primary sources in the coastal plain: (a) direct feeding from the rocks of Uruguay and Rio Grande do Sul Shield and Parana Basin, drained by Rio Camaqua and Rio Jacui; and (b) indirect feeding from rocks of the Andean province, drained by Rio Parana and Rio La Plata estuary in northern Argentina. During low sea level, rivers flowed directly into the continental shelf, and their deposits were reworked during subsequent transgressive stages. Throughout this region, the atmospheric circulation pattern forms a NW oceanic swell, generating a longshore current with dominant northward direction. Thus, several transgressive-recessive pulses associated with Pleistocene glacial events pushed large volumes of sediments northward, giving rise to the present southern Brazil coastal plain.

Provenance of heavy minerals in the Quaternary deposits of the Lemme outcrop, Estonia, based on optical microscopy, X-ray diffractometry and scanning electron microscope microanalysis

Provenance of heavy minerals in the Quaternary deposits of the Lemme outcrop, Estonia, based on optical microscopy, X-ray diffractometry and scanning electron microscope microanalysis

Correlation of Hydrocarbon Reservoir Sandstones Using Heavy Mineral Provenance Signatures: Examples from the North Sea and Adjacent Areas

Correlation of hydrocarbon reservoir sandstones is one of the most important economic applications for heavy mineral analysis. In this paper, we review the fundamental principles required for establishing correlation frameworks using heavy mineral data, and illustrate the applications of a wide variety of heavy mineral techniques using a number of case studies from hydrocarbon reservoirs in the North Sea and adjacent areas. The examples cover Triassic red-bed successions in the central North Sea and west of Shetland, which have been subdivided and correlated using provenance-sensitive ratio data and mineral morphologies; Middle Jurassic paralic sandstones in the northern North Sea, correlated using garnet geochemistry; Upper Jurassic deep water sandstones in the northern North Sea, discriminated using rutile geochemistry and detrital zircon age data; and the “real-time” application of the technique at well site in Devonian-Carboniferous fluvio-lacustrine sandstones of the Clair Field, west of Shetland.

Single grain heavy mineral provenance of garnet and amphibole in the Surveyor fan and precursor sediments on the Gulf of Alaska abyssal plain — Implications for climate-tectonic interactions in the St. Elias orogen

The St. Elias orogen formed as a result of the northwestward drift of the Yakutat terrane along and final collision with the Alaska margin in the Miocene. Its exhumation coincided with changing glacial conditions that are considered to have strongly interacted with mountain building processes. A significant part of the record of these tectonic-climatic interactions is stored in sediments on the Gulf of Alaska abyssal plain including the Surveyor fan. Our study examines temporal provenance changes of Miocene through Pleistocene sediments of the Surveyor fan, Gulf of Alaska, to constrain the dynamics of exhumation and mass transfer from the evolving St. Elias orogen to the adjacent Surveyor deep sea fan. We present single grain geochemical data of amphibole and garnet and 40Ar/39Ar cooling ages of biotite and amphibole together with point counting data of heavy minerals from sands and silts from two sites in the distal and proximal fan, drilled by IODP expedition 341 in 2013 (sites U1417 and U1418, respectively).A shift in heavy mineral composition during the Miocene, predating the onset of glaciation, points to a tectonically-induced change in erosion centers and sediment transport, probably caused by the rise of the St. Elias Mountains. Garnet and amphibole data suggest the Chugach metamorphic complex is the main sediment source, implying input to the Surveyor fan from sources relatively far in the north during the Miocene. Changing provenance signals from the Miocene to Pliocene suggest rising input from the lower grade metamorphic areas at the southern flanks of the orogen, indicating the advance of glaciers to the tidewater line, providing material from this flanking region. Higher input from the Chugach metamorphic complex in all Pleistocene sediments suggests the Northern Hemisphere glaciation at the Plio-Pleistocene boundary caused erosion and sediment yield from the interior of the orogen. Climatic changes at the mid-Pleistocene transition did not cause significant changes in the provenance signal.

Provenance of heavy minerals from recent sediments of Balakyan River, Kurdistan Region, Iraq

Heavy mineral assemblages of the sediments in Balakyan River have been studied to determine their concentrations and provenance. Twelve sediment samples were analyzed for heavy mineral assemblage determination. The unstable heavy minerals (pyroxene and amphibole) represent more than 50%. The mineral chemistry and petrographic studies refer to the predominant clinopyroxene mineral is diopside. Actinolite, tremolite, and magnesiohornblende are common calc-amphibole in the sediments. The ultrastable heavy minerals are present in trace amounts. According to the mineral chemistry the clinopyroxene is derived from basic igneous rocks crystallized at 1150-1220⁰C and low pressure. Amphibole and epidote crystallized under low temperature and/or formed under low grade metamorphism. The detrital chromian spinel is derived from basic and ultrabasic igneous rocks of Alpine type peridotite formed in fore-arc. The probable source of these assemblages is Ophiolite Complex to the north of the studied area (north Iraq) and igneous parts of Walash Series and Red Bed Series also the sedimentary rocks of Shiranish and Tanjero formations.

Distribuição espacial de minerais pesados nos sedimentos superficiais da Plataforma Continental Oeste do Ceará, Nordeste do Brasil

Os sedimentos da plataforma continental oeste cearense foram investigados com relação à sua textura, conteúdo de carbonato de cálcio e minerais pesados com a geração do modelo digital de fundo desta plataforma. A estatística multivariada foi aplicada aos dados mineralógicos para auxiliar na interpretação da proveniência dos minerais pesados. A plataforma continental oeste cearense, apesar da predominância da sedimentação carbonática, apresenta concentrações importantes de minerais pesados (4,54 %), originando depósitos do tipo plácer nas areias litoclásticas e litobioclásticas situadas mais a leste da área estudada (Folha Fortaleza). Foram identificadas irregularidades indicativas de paleocanais e antigas linhas de praia que favorecem a concentração de minerais pesados. A assembleia mineral (ilmenita, turmalina, epídoto, hornblenda, monazita, estaurolita, sillimanita, rutilo, magnetita, zircão, andaluzita, cianita, granada, leucoxênio, diopsídio, apatita, espinélio e cassiterita) sugere contribuições regionais do retrabalhamento dos sedimentos da Formação Barreiras e contribuição local das rochas metamórficas do Complexo Ceará. Afloramentos do embasamento cristalino na plataforma continental próximos ao Porto do Pecém (São Gonçalo do Amarante) contribuem diretamente no aporte de sedimentos terrígenos e são nesses locais que os minerais pesados se concentram. A estatística multivariada discriminou os dois tipos de proveniências anteriormente descritos, contudo devem-se levar em consideração outras contribuições como das areias pretas costeiras, aporte fluvial atual (continental) e pretérito (vales fluviais afogados) e sedimentos marinhos de deriva litorânea.

The provenance of Borneo's enigmatic alluvial diamonds: A case study from Cempaka, SE Kalimantan

Gem-quality diamonds have been found in several alluvial deposits across central and southern Borneo. Borneo has been a known source of diamonds for centuries, but the location of their primary igneous source remains enigmatic. Many geological models have been proposed to explain their distribution, including: the diamonds were derived from a local diatreme; they were brought to the surface through ophiolite obduction or exhumation of UHP metamorphic rocks; they were transported long distances southward via major Asian river systems; or, they were transported from the Australian continent before Borneo was rifted from its northwestern margin in the Late Jurassic. To assess these models, we conducted a study of the provenance of heavy minerals from Kalimantan's Cempaka alluvial diamond deposit. This involved collecting U–Pb isotopic data, fission track and trace element geochemistry of zircon as well as major element geochemical data of spinels and morphological descriptions of zircon and diamond. The results indicate that the Cempaka diamonds were likely derived from at least two sources, one which was relatively local and/or involved little reworking, and the other more distal which records several periods of reworking. The distal diamond source is interpreted to be diamond-bearing pipes that intruded the basement of a block that: (1) rifted from northwest Australia (East Java or SW Borneo) and the diamonds were recycled into its sedimentary cover, or: (2) were emplaced elsewhere (e.g. NW Australia) and transported to a block (e.g. East Java or SW Borneo). Both of these scenarios require the diamonds to be transported with the block when it rifted from NW Australia in the Late Jurassic. The local source could be diamondiferous diatremes associated with eroded Miocene high-K alkaline intrusions north of the Barito Basin, which would indicate that the lithosphere beneath SW Borneo is thick (~150km or greater). The ‘local’ diamonds could also be associated with ophiolitic rocks that are exposed in the nearby Meratus Mountains.

Constraining the origin of reservoirs formed by sandstone intrusions: Insights from heavy mineral studies of the Eocene in the Forties area, United Kingdom central North Sea

The presence of hydrocarbon-bearing sandstones within the Eocene of the Forties area was first documented in 1985, when a Forties field (Paleocene) development well discovered the Brimmond field. Further hydrocarbons in the Eocene were discovered in the adjacent Maule field in 2009. Reservoir geometry derived from three-dimensional seismic data has provided evidence for both a depositional and a sand injectite origin for the Eocene sandstones. The Brimmond field is located in a deep-water channel complex that extends to the southeast, whereas the Maule field sandstones have the geometry of an injection sheet on the updip margin of the Brimmond channel system with a cone-shape feature emanating from the top of the Forties Sandstone Member (Paleocene). The geometry of the Eocene sandstones in the Maule field indicates that they are intrusive and originated by the fluidization and injection of sand during burial. From seismic and borehole data, it is unclear whether the sand that was injected to form the Maule reservoir was derived from depositional Eocene sandstones or from the underlying Forties Sandstone Member. These two alternatives are tested by comparing the heavy mineral and garnet geochemical characteristics of the injectite sandstones in the Maule field with the depositional sandstones of the Brimmond field and the Forties sandstones of the Forties field. The study revealed significant differences between the sandstones in the Forties field and those of the Maule and Brimmond fields), both in terms of heavy mineral and garnet geochemical data. The Brimmond-Maule and Forties sandstones therefore have different provenances and are genetically unrelated, indicating that the sandstones in the Maule field did not originate by the fluidization of Forties sandstones. By contrast, the provenance characteristics of the depositional Brimmond sandstones are closely comparable with sandstone intrusions in the Maule field. We conclude that the injectites in the Maule field formed by the fluidization of depositional Brimmond sandstones but do not exclude the important function of water from the huge underlying Forties Sandstone Member aquifer as the agent for developing the fluid supply and elevating pore pressure to fluidize and inject the Eocene sand. The study has demonstrated that heavy mineral provenance studies are an effective method of tracing the origin of injected sandstones, which are increasingly being recognized as an important hydrocarbon play.

Heavy mineral provenance of the Mesozoic succession in Andøya, northern Norway: implications for sand transport in the Vøring Basin

Abstract A heavy mineral, mineral chemical and detrital zircon study of Jurassic–Cretaceous (Bathonian–Valanginian) sandstones of the Andøya B borehole, Lofoten–Vesterålen, northern Norway, has revealed the existence of significant differences within the succession. These are related partly to changes in source and partly to variations in the extent of weathering during alluvial storage. Three mineralogical units have been identified. The main change takes place within the Bathonian, and is interpreted as marking a switch from eastern (West Troms) to western (Andøya–Lofoten High) sourcing, consistent with previously published sedimentological models. U–Pb age data indicate that most of the zircons were derived from Palaeoproterozoic rocks ( c. 1750–1860 Ma), with a subordinate Archaean group ( c. 2600–2800 Ma) and a small early Palaeozoic group (mostly in the 435–446 Ma range). These groups can all be tied back to lithological components of the Lofoten–Vesterålen and West Troms regions, including Palaeozoic rocks hosted in Caledonian allochthons. The provenance characteristics of the Andøya succession have no counterpart in Cretaceous and Paleocene sandstones of the Vøring Basin. This suggests that sediment fed into the basin from Lofoten–Vesterålen was of minor importance, and that prospective Cretaceous–Paleocene hydrocarbon reservoir sandstones in the Vøring Basin were mainly derived from either northern Nordland or northern East Greenland. Supplementary material: Zircon isotopic compositions and ages are available at http://www.geolsoc.org.uk/SUP18616 .

Early–Middle Miocene (17–14 Ma) Antarctic ice dynamics reconstructed from the heavy mineral provenance in the AND-2A drill core, Ross Sea, Antarctica

The Miocene Climatic Optimum (17–15Ma) and the rapid cooling of the Middle Miocene Climate Transition (15–13Ma) together signal a major change in Earth's climate system. Here we examine the sediment provenance in the AND-2A drill core, located 10km from the East Antarctic coastline, to significantly increase our understanding of Antarctic ice development, glacial erosion, and transport in the Ross embayment during this time. Heavy minerals are very diagnostic of source rock types and assemblages can be used to track changes in the areas of maximum erosion under the margin of an ice sheet. We used a combination of optical mineralogy and SEM-EDS analysis to characterize the heavy mineral fractions of diamictites and sandstones in the upper 650m of AND-2A, which includes an expanded section dated between ~17 and 14Ma. We find four diagnostic heavy mineral assemblages distributed in intervals throughout the core: I. (650–552mbsf) elevated orthopyroxene, titanaugite, and carbonate contents; II. (552–308mbsf) abundant diopside, pigeonite, and orthopyroxene, with sillimanite and kyanite; III. (308–250mbsf) increasing contents of garnet and green hornblende; and IV. (250–20mbsf) abundant green hornblende, titanaugite, green augite, and carbonate. Based on the heavy mineral analysis we demonstrate that (1) the ice sheet was grounded on the shelf at ~17.7–17.1Ma, and it was eroding Cenozoic volcanic rocks to the south of the drillsite; (2) during the early part of the Miocene Climatic Optimum (~17.1–15.5Ma) the East Antarctic Ice Sheet retreated landward into upland regions of the Transantarctic Mountains, where it eroded dolerite sills and high-grade metamorphic rocks; (3) immediately prior to the Middle Miocene Climate Transition (15.5–14.3Ma), the East Antarctic ice advanced and eroded granitic and low-medium grade metamorphic basement rocks in the coastal sections of the Transantarctic Mountains; and (4) following this initial phase of ice growth, the West Antarctic Ice Sheet and the East Antarctic Ice Sheet coalesced into a larger than modern (interglacial) Antarctic Ice Sheet prior to 14.3Ma and eroded Cenozoic volcanic and low- to medium-grade metamorphic basement rocks to the south of the drillsite. Our results suggest that, although East Antarctica may have remained glaciated during the Miocene Climatic Optimum, ice extent was reduced to a configuration within the present interglacial extent, even during orbital-scale glacial maxima. Ice growth during the Middle Miocene Climate Transition commenced at ca. 15.5Ma in the Ross Sea basin, which is slightly earlier than inferred from deep-sea stable isotope records, but in agreement with low-latitude sea-level reconstructions.

Jurassic to Palaeogene tectono‐magmatic evolution of northern Chile and adjacent Bolivia from detrital zircon U‐Pb geochronology and heavy mineral provenance

Terra Nova, 23, 399–406, 2011AbstractHeavy mineral provenance data presented in this article reinforce evidence for significant late Palaeogene deformation and relief formation along the western margin of the Central Andean Plateau. Late Eocene–Oligocene onset of molasse‐type sedimentation records initial range uplift. Strikingly different basement sources of sediments deposited to the east and west of the Late Palaeogene range indicate that initial relief development was governed by a bivergent thrust system. Significantly higher sediment accumulation rates to the east of the range compared to the west suggest that the generated relief acted already as an effective orographic barrier at that time. Higher precipitation and denudation along the eastern slope facilitated deeper erosion of the trust belt.

Textural characteristics, distribution pattern and provenance of heavy minerals in glacial sediments of Schirmacher Oasis, east Antarctica

Heavy minerals of twenty sediment samples, belonging to polar ice sheet, lake, mainland area and shelf region of Schirmacher Oasis, east Antarctica, have been studied for their textural characteristics, abundance and provenance determination. The heavy crop is represented by zircon, tourmaline, rutile, garnet, hypersthene, hornblende, chlorite, enstatite, lawsonite, kyanite, sillimanite, zoisite, andalusite, spinel, topaz and opaques. The assemblage, in general, is dominated by hornblende-hypersthene-garnet assemblage, followed by kyanite-sillimanite-andalusite and zircontourmaline-rutile. The high concentration of specific minerals of metamorphic origin reveals high-grade metamorphic terrain as the primary source. The ZTR ratio is low showing low mineralogical maturity. An attempt has also been made to compare the trends of heavy minerals of various sub glacial regions with those of the average values of entire area.

Provenance of heavy-minerals in the Piranhas-Acu River, Northeastern Brazil

Clino-amphibole, epidote, garnet, sillimanite, tourmaline, staurolite, andalusite, zircon, rutile, augite, ilmenite, hematite and magnetite are the heavy-minerals recorded in the Piranhas-Acu River. Six assemblages were identified: (i) Garnet-hornblende-tourmaline with sillimanite, when cutting rocks of the Serido Formation; (ii) Hornblende-garnet-zircon, when crossing rocks of the Caico gneiss-migmatite Complex; (Hi) Hornblende-zircon-epidote-staurolite, when in rocks of the Jucurutu Formation; (iv) Hornblende-zircon-epidote, when rocks of the Acu Formation; (v) Hornblende-zircon-staurolite, when the lowermost Agu River channel cuts limestones of the Jandaira Formation, and (vi) Zircon-tourmaline-staurolite in the Acu River mouth (Cenozoic rocks) where coastal dynamics dominate. Mineral ratios that reflect differences in grain shape, density, and selective chemical decomposition were used to isolate the effects of source and as controls of mineral variability. The reworking of the sediments was regionally effective in selective sorting; the more equant minerals (e.g. epidote) and heavier minerals (e.g. opaques) had a higher probability of being selected for permanent deposition during reworking. The process of selective decomposition dominates at the river mouth.