Abundance Of Heavy Minerals Research Articles

Synergistic Application of Geoelectrical Methods for Mapping Placers along the Coastal Periphery of Southern Odisha, India

ABSTRACT This study examines the distribution and amount of placer deposits enriched with heavy minerals along the coastal region of Odisha, India utilizing a combination of geoelectrical techniques. Abundant heavy mineral placers have been identified along the southern coast of Odisha. However, while geological investigations have been conducted, there is a notable absence of geophysical analyses in this specific area. To ascertain both the horizontal and vertical extensions of heavy mineral placer deposits, a comprehensive investigation was undertaken, involving the execution of 23 ERT (Electrical Resistivity Tomography) and TDIP (Time-Domain Induced Polarization) profiles within the designated study zone. These profiles unveiled substantial heavy-mineral zones spanning from shallow layers to depths of approximately 10-15 m. Two primary patterns of mineralization were discerned: firstly, dispersed occurrences which manifested closer to the surface, characterized by irregular black patches of minerals; secondly, concentrated mineralization found at moderate to significant depths, hinting at concealed or buried deposits. Considering the presence of conductive minerals (ilmenite, magnetite) within the beach placers of the study locale, the application of ERT and IP methods proved to be viable. Additionally, the mineralization trends exhibited variance as one traversed from the southwest to the northeast within the study area. Notably, the resistivity of the heavy minerals ranged from 0.1 to 1.1 Ωm, coupled with chargeabilities surpassing 20 mV/V. Significantly, the arrangement of alternating heavy mineralization layers within the sand formations implied the potential presence of stratal anisotropy. Consequently, a specialized code was developed and implemented to perform 2D anisotropic inversion of the ERT data. The application of this anisotropic inversion rectified the depth estimations for concealed pockets of heavy mineralization. While conventional isotropic inversion suggested a concealed mineralization pocket at depths of 15-32 m, the anisotropic inversion revealed that the same mineral-bearing strata existed at depths of 16–28 m.

Discrimination of tectonic provinces using zircon U-Pb ages from bedrock and detrital samples in the northern Andes

Abstract The northern Andes of southern Colombia contain a rich geologic history recorded by Proterozoic to Cenozoic metamorphic, igneous, and sedimentary rocks. The region plays a pivotal role in understanding the evolution of topography in northwestern South America and the development of large river systems, such as the Amazon, Orinoco, and Magdalena rivers. However, understanding of the basement framework has been hindered by challenging access, security concerns, tropical climate, and outcrop scarcity. Further, an insufficient geochronologic characterization of Andean basement complicates provenance interpretations of adjacent basins and restricts understanding of the paleogeographic evolution of southern Colombia. To address these issues, this paper presents a zircon U-Pb geochronological dataset derived for 24 bedrock samples and 19 modern river samples. The zircon U-Pb results reveal that the Eastern Cordillera of southern Colombia is underlain by basement rocks that originated in various tectonic events since ca. 1.5 Ga, including the accretion of discrete terranes. The oldest rocks, found in the Garzon Massif, are high-grade metamorphic rocks with contrasting Proterozoic protolith crystallization ages. Whereas the SW part of the massif formed during the Putumayo Orogeny (ca. 1.2–0.9 Ga), we report orthogneisses for the NE segment with protoliths formed at ca. 1.5 Ga, representing the NW continuation of the Rio Negro Jurena province of the Amazonian Craton. In contrast, crystalline rocks of the Central Cordillera primarily consist of Permian–Triassic (ca. 270–250 Ma) and Jurassic–Cretaceous (ca. 180–130 Ma) igneous rocks formed in a magmatic arc. In southernmost Colombia, the Putumayo Mountains mainly consist of Jurassic–Cretaceous (180–130 Ma) plutonic and volcanic rocks. Furthermore, we analyzed the heavy mineral abundances in modern river sands in southern Colombia (spanning 1°N–5°N) and found that key minerals such as garnet and epidote can be utilized to trace high-grade metamorphic and igneous lithologies, respectively, in the river catchments. The differentiation of basement ages for separate tectonic provinces, combined with heavy mineral abundances in modern sands, can serve as unique fingerprints in provenance analyses to trace the topographic and exhumational evolution of different Andean regions through time.

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 of modern sands from Baja California rivers (Mexico): petrographic constraints from light and heavy minerals

ABSTRACT We used high-resolution petrographic and dense-mineral data on modern sand to investigate erosion patterns of the El Rosario, San Fernando, and San Vicente river basins of Baja California (Mexico) to better understand the interrelationships between a complex magmatic arc terrane and surface processes. Modern sand composition of these three rivers reflects the nature of the source region, which lies in the central part of the Alisitos arc (Peninsular Ranges, Baja California, Mexico). The sand detrital modes correspond well with the main structural units drained by the El Rosario, San Fernando, and San Vicente rivers: 1) the Early Cretaceous oceanic arc of the Alisitos Group, 2) the Paleozoic to Mesozoic continental-margin metasedimentary rocks, 3) the Cretaceous plutons, 4) the Upper Cretaceous to Tertiary sedimentary rocks, and 5) the Tertiary volcanics. The modern sand of the San Vicente, San Fernando, and El Rosario rivers is fed chiefly from erosion of a magmatic arc and consists mostly of minor feldspatho-lithic (Fl) to quartzo-litho-feldspathic (qFL) sand and dominant quartzo-feldspatho-lithic (qLF) and litho-feldspatho-quartzose (lQF) sand. Framework petrography also suggests a progressive increase in quartz, K-feldspar, sedimentary and metamorphic lithic fragments, and a decrease in volcanic lithic fragments. Sand, in the Lv field, microlitic (Lvmi), felsitic (Lvf) and lathwork (Lvl) types, and trace amounts of vitric grains (Lvv), such as pumice particles. The andesitic volcanic province of the Alisitos arc sheds quartz-poor sand containing mainly microlitic lithic fragments and plagioclase, whereas sand derived from more felsic rhyolites and rhyodacitic and trachyandesitic products contains largely felsitic volcanic lithics and minor lathwork lithics are mainly derived from subordinate basalts. The abundance of intrusive rock fragments and volcanic and sedimentary lithics of the sampled river sands faithfully represents the relative abundance of a heterogeneous bedrock exposure consisting of sedimentary and metasedimentary rocks, as well as volcanic, plutonic, and medium- to high-grade metamorphic rocks in each drainage basin. Transparent heavy-mineral assemblages including major amounts of amphibole, pyroxene, epidote, titanite, zircon, and minor amounts of staurolite, rutile, actinolite, tourmaline, garnet, kyanite, andalusite, sillimanite, and apatite are in good agreement with a mixed provenance characterized mainly by magmatic, primarily volcanic (andesite, rhyolite, and basalt) and secondarily plutonic (granitoid rocks) and metamorphic source rocks. Some labile species such as hornblende and pyroxene grains show mainly corroded to etched morphologies due to dissolution processes and by chemical weathering processes occurring in a paleo and current semiarid climate. The Zircon+Tourmaline+Rutile index of the heavy-mineral modes, coupled with their subrounded to rounded grain surface texture, indicates recycling from the sedimentary source rocks. Heavy-mineral abundance and weathering textures in the San Fernando and San Vincente river sands match predominantly volcanic bedrock lithologies, while the El Rosario river sands match sedimentary and metasedimentary source rocks.

Sediment provenance of the Lulehe Formation in the Qaidam basin: Insight to initial Cenozoic deposition and deformation in northern Tibetan plateau

AbstractUnravelling early Cenozoic basin development in northern Tibetan Plateau remains crucial to understanding continental deformation mechanisms and to assessing models of plateau growth. We target coarse‐grained red beds from the Cenozoic basal Lulehe Formation in the Qaidam basin by combining conglomerate clast compositions, paleocurrent determinations, sandstone petrography, heavy mineral analysis and detrital zircon U–Pb geochronology to characterize sediment provenance and the relationship between deformation and deposition. The red beds are dominated by matrix‐supported, poorly sorted clastic rocks, implying low compositional and textural maturity and short transport distances. Although most sandstones have high (meta)sedimentary lithic fragment contents and abundant heavy minerals of metamorphic origin (e.g., garnet, epidote and chlorite), spatiotemporal differences in detrital compositions are evident. Detrital zircon grains mainly have Phanerozoic ages (210–280 Ma and 390–480 Ma), but Proterozoic ages (750–1000 Ma, 1700–2000 Ma and 2300–2500 Ma) are also prominent in some samples. Analysed strata display dissimilar (including south‐, north‐ and west‐directed) paleocurrent orientations. These results demonstrate that the Cenozoic basal deposits were derived from localized, spatially diverse sources with small drainage networks. We advocate that initial sedimentary filling in the northern Qaidam basin was fed by parent‐rocks from the North Qaidam‐South Qilian belts and the pre‐Cenozoic basement within the Qaidam terrane interior, rather than southern distant Eastern Kunlun regions. Seismic and drilling well stratigraphic data indicate the presence of paleohighs and syn‐sedimentary reverse faults and noteworthy diversity in sediment thickness of the Lulehe Formation, revealing that the Qaidam terrane exhibited as several isolated depocenters, rather than a coherent basin, in the early stage of the Cenozoic deposition. We suggest the Cenozoic Qaidam basin to have developed in a contractional deformation regime, which supports models with synchronous deformation throughout most of Tibet shortly after the India‐Eurasia collision.

The Role of Heavy Minerals in Understanding the Provenance of Sandstone: An Example from the Upper Cretaceous Tanjero Formation, Surdash Region, Northeastern Iraq

The Tanjero Formation is the Upper Cretaceous (Campanian-Maastrichtian) crops out in northeastern Iraq at the High-Folded and Imbricate Zones. To study heavy minerals, twenty sandstone samples were obtained from selected sites of the Tanjero Formation exposed at the southwestern limb of the Surdash anticline in the northeast part of Sulaimanyia city. The analyzed data indicates that the most abundant heavy minerals are opaque, followed by pyroxene, epidote, amphibole, chlorite, rutile, and garnet. The significant abundance of unstable and metastable minerals in the heavy mineral suites shows their direct derivation from the adjacent main basic igneous and metamorphic source rocks, which are situated in the High-Folded and Imbricate Zones in the northern and northeastern parts of Iraq. The estimated zircon-tourmaline-rutile index reveals that the majority of the sandstone samples have less than 75% zircon-tourmaline-rutile index, indicating that the sediments are generally immature. Furthermore, the relationship between an ultra-stable and a meta-stable heavy mineral indicated the immaturity of the Tanjero Formation sandstone and its moderate stability, proving that these minerals cannot be transported over extremely long distances close to the source rocks area. The heavy mineral assemblage demonstrated that the studied area is distinguished by high tectonic activity. In addition, according to the MF- MT-GM ternary diagram, the analyzed sandstone samples lie within the active continental margins field, which is distinguished by a higher percentage of MF minerals than GM minerals generated from mafic magmatic source rocks.

Provenance studies on the heavy mineral placers along the coastal deposits of Odisha, eastern India

The coastal deposits along the eastern part of the Indian Peninsula are known for the high abundance of heavy minerals. The present study, as discussed here, has been undertaken along the south-western coastal part of Odisha, India, adjoining the charnockite–migmatite zone of the Eastern Ghat Mobile Belt (EGMB). The composition of the placers along the study area is primarily controlled by the detritus from the proximal hinterland rock type(s). The weathering index has been established based on the grain morphology, major element concentration and radioelement ratios. Petrological characteristics and grain morphology of monazite, zircon, ilmenite and rutile have been presented respectively, and their implications are discussed. The provenance study of these coastal placers is based on the abundance of rare earth elements (REE) and radioactive elements in the placer sands and the rock types in the study area. The tectonic implications are based on the major element abundance of the beach sands.

Jingwenite-(Y) from the Yushui Cu deposit, South China: The first occurrence of a V-HREE-bearing silicate mineral

Abstract Jingwenite-(Y), Y2Al2V24+(SiO4)O4(OH)4, the first V-HREE-bearing silicate mineral discovered in nature, is an abundant component of a sediment-hosted stratiform Cu (SSC) deposit, Yushui, South China. The mineral occurs in bedded/massive sulfide-bearing ore and is associated with bornite, chalcopyrite, galena, xenotime-(Y), nolanite, thortveitite, roscoelite, barite, and quartz. Optically, jingwenite-(Y) is biaxial (+), with α = 1.92(4), β = 1.95(2), γ = 1.99(3) (white light), and 2V (calculated) = 83°. The dispersion is medium with r < v, and the pleochroism is with X = light brown, Y = brown, Z = dark brown. The color, streak, luster, and hardness (Mohs) are light brown, yellowish gray, vitreous, and 4½–5, respectively. Jingwenite-(Y) is monoclinic, with space group I2/a, Z = 4, and unit-cell parameters a = 9.4821(2) Å, b = 5.8781(1) Å, c = 19.3987(4) Å, β = 90.165(2)°, and V = 1081.21(4) Å3. The structure of jingwenite-(Y) has chains of edge-sharing Al(V,Fe)-O octahedra and V(Ti)-O octahedra extending along the b-axis and linked by insular Si-O tetrahedra, leaving open channels occupied by HREEs. Jingwenite-(Y) is a new nesosilicate structural type. Sm-Nd dating and Nd isotope signatures of jingwenite-(Y) reveal an epigenetic origin and suggest that HREEs and V were added to the SSC system via leaching of abundant heavy minerals in the footwall red sandstone by oxidized basinal brines. The abundance of jingwenite-(Y) at Yushui indicates that it could potentially be a valuable resource for HREE and V. Moreover, HREE and V mineralization can also occur in the same sediment-hosted Cu mineral system.

Sedimentary records of the Yangtze Estuary over the past 70 years and their implications for provenance

The Yangtze River is the largest river in southern China. In this study, the two sediment cores (CM-A and NH-C) taken from the Yangtze River Estuary were analyzed for 210Pb and 137Cs dating, major and trace elements, rare earth elements (REEs) and grain size of sediments. The results showed that the sedimentary ages of CM-A and NH-C cores were 37 and 64 years respectively. Then the major and trace elements in the sediments of the Yangtze Estuary were derived from terrigenous clastic materials. The chemical index of alteration (CIA) in the two cores ranged between 57 and 70, 66 and 73, respectively, reflecting the low to intermediate intensity of chemical weathering in the provenance area. The abundance of heavy minerals, grain size in hydrodynamically sorted, and chemical weathering have less effect on REE chemistry in the core CM-A, as well as the source of sediments in the core CM-A can be identified. By comparing the geochemical elements of sediments from the Yangtze River Basin, The provenance of sediments in the upper reaches of the Yangtze River might be similar to those of core CM-A sediments. Combined with A-CN-K and La-Th-Sc ternary diagrams and source discrimination diagrams of REEs parameters, it was presumed that the samples were influenced by K metasomatism, and originated from the same source area, and the granodiorite was the most probably source rock of these samples. Therefore, the upper reaches of the Yangtze River are considered to be the main source area of the sediments core CM-A.

Seasonal variations of textural and heavy minerals of the Karamana river sediments and beach sediments of Trivandrum, Southern Kerala

Kerala, south western state of India is known for its abundant heavy mineral deposits along the coast. Beach placer deposits in Kerala is known for ilmenite, rutile, zircon, monazite, sillimanite and garnet. The grain size study of the sediments from Karamana river, flowing in the southern part of Kerala. Sediments from different parts of the river basin is studied, which enabled to understand the grain size variations with course of the river from the Peppara dam to Thiruvallam, very near to coast. Mineralogy of the river vary from one place to another depending different factors like host rocks in the province, climate conditions of the area, agents of transport and hydraulic condition during deposition, also can predict the actual source area associated with heavy mineral. Textural and heavy mineral studies of the placers of beach and Karamana river basins indicating the river is one of the important contributors of sediments to the western coast of the southern part of Kerala. Samples from various parts of the river indicate that the sediment is medium sand, moderately sorted, fine skewed and platykurtic. The characteristics of grain size distribution are related to the source rocks, process of weathering, and different sorting processes during transportation and deposition. The total heavy mineral percentage shows it is prominently enrichment in fine sand and very fine sands.

Geochemical Characterization and Presence of Rare Earth Elements in the Recent Depositions at the Islands of the Eastern Bay of Bengal, Bangladesh

This study presents geochemical characterization, as well as, quantification of rare earth elements in the recent beach deposition at the two major islands of the eastern Bay of Bengal-Kutubdia and Moheshkhali. Placer sand samples from near surface depositions were analyzed by heavy mineral separation, mineralogical identification, chemical composition and elemental mapping. X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used to obtain these results. The heavy mineral concentration in different raw sand samples resulted by heavy liquid separation technique revealed that the average abundance of heavy minerals is 69.67% in Kutubdia island and 9.32% in Moheshkhali island, respectively. The X-ray patterns of Kutubdia and Moheshkhali sand samples show the presence of zircon, quartz, hematite, magnetite, ilmenite, chromite, kyanite, anatase, rutile and garnet. Chemical composition of heavy mineral sands from Kutubdia and Moheshkhali islands were analyzed using X-ray fluorescence method (XRF) for major oxides and trace elements. The concentration is of Na2O, MgO, Al2O3, SiO2, P, K2O, CaO, TiO2, V2O5, Cr2O3, MnO, Fe2O3, CoO, ZnO, SrO, Y2O3 ZrO2, Nb2O5, MoO3, HfO2, WO3, ThO2, U3O8, CeO2, Nd2O and Er2O3 were determined. A significant amount of various rare earth elements (REEs) in the elemental composition of few samples was also identified. The study is expected to be useful in the baseline and environmental aspects of both the islands.

Detection of mineralogically accentuated biogenic structures with high-resolution geophysics: implications for ichnology and geoecology

Identification and mapping of small-scale physical and biogenic structures in sand has been a challenge to sedimentologists and ichnologists. Under natural conditions, biogenic activity (trampling tracks, burrows) alter primary sedimentary structures, but also serve as important paleoenvironmental indicators of geotechnical properties of sediments, omission surfaces, and ecosystem dynamics. Therefore, the ability to recognize such structures as anomalies in shallow subsurface, especially when using indirect non-invasive methods, such as geophysical imaging, is an important aspect of assessing their relative contribution to the overall erosional-depositional record. This study presents experimental evidence of the viability of two highresolution geophysical methods in detecting sediment deformation that mimics shallow animal traces. High-frequency (800 MHz) ground-penetrating radar (GPR) imaging aided in visualizing a buried depression produced by a deer hoofprint cast indenter, with high-amplitude reflection return enhanced by a heavy-mineral concentration (HMC). Bulk in situ low-frequency (930 Hz), low-field magnetic susceptibility (MS) experiment supported the theoretical pattern of a decrease in MS over the thickest cover sand (maximum indentation depth) to ~0 mSI and the highest values over raised HMC horizon (marginal ridge; >8 mSI). Because both methods are affected by the presence and relative abundance of heavy minerals, the present approach can be applied in most siliciclastic settings. This study demonstrates the promise of extending the 2D visualization of subsurface targets to 3D datasets, with potential implications for sedimentological, ichnological, archaeological, and geoecological research that involves animal-sediment interaction at different scales.

Geochemical Characterization and Presence of Rare Earth Elements in the Recent Depositions at the Islands of the Eastern Bay of Bengal, Bangladesh

This study presents geochemical characterization, as well as, quantification of rare earth elements in the recent beach deposition at the two major islands of the eastern Bay of Bengal-Kutubdia and Moheshkhali. Placer sand samples from near surface depositions were analyzed by heavy mineral separation, mineralogical identification, chemical composition and elemental mapping. X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used to obtain these results. The heavy mineral concentration in different raw sand samples resulted by heavy liquid separation technique revealed that the average abundance of heavy minerals is 69.67% in Kutubdia island and 9.32% in Moheshkhali island, respectively. The X-ray patterns of Kutubdia and Moheshkhali sand samples show the presence of zircon, quartz, hematite, magnetite, ilmenite, chromite, kyanite, anatase, rutile and garnet. Chemical composition of heavy mineral sands from Kutubdia and Moheshkhali islands were analyzed using X-ray fluorescence method (XRF) for major oxides and trace elements. The concentration is of Na2O, MgO, Al2O3, SiO2, P, K2O, CaO, TiO2, V2O5, Cr2O3, MnO, Fe2O3, CoO, ZnO, SrO, Y2O3 ZrO2, Nb2O5, MoO3, HfO2, WO3, ThO2, U3O8, CeO2, Nd2O and Er2O3 were determined. A significant amount of various rare earth elements (REEs) in the elemental composition of few samples was also identified. The study is expected to be useful in the baseline and environmental aspects of both the islands.

Heavy Minerals as Indicators of the Source and Stratigraphic Position of the Loess-Like Deposits in the Orava Basin (Polish Western Carpathians)

This study is focused on the loess-like deposits accumulated on glaciofluvial fans of the Czarny Dunajec River in the Orava Basin (Southern Poland). The deposition of these sediments took place during three cold intervals of the Pleistocene: Würm, Riss, and Günz/Mindel. So far, the provenance and age of the deposits has not been precisely defined, even though the development of each fan is believed to be related to the successive glacial periods in the Tatra Mountains. Heavy minerals were studied to determine the source of the deposits. Heavy mineral analyses revealed that zircon, tourmaline, rutile, garnet, amphibole, epidote, and apatite are the typical constituents of the heavy mineral fraction. Abundances of heavy minerals differ in each of the Pleistocene fans of the Czarny Dunajec River, especially the amphibole content. However, the chemical composition of garnet, amphibole, and tourmaline is rather uniform. This research showed that mainly medium-grade metamorphic rocks with a subordinate share of high-grade metamorphics, and granitic rocks are the dominant source rocks of the deposits studied. Such rocks are exposed in the Western Tatra Mountains, which most probably supplied the Orava Basin with clastic material. Change in abundances of heavy minerals in the succession may reflect the progressive erosion of the source area. Grain-size distribution and textural features of the sampled sediments suggest fluvial and aeolian modes of transportation. Additionally, this study indicated that heavy minerals may be used to correlate the loess covers in the Orava Basin.

Mineralogical Studies of Kerur Formation Badami Group, Kaladgi Basin, Karnataka

Abstract Heavy and clay mineral analysis is a significant tool to interpret the provenance and paleoclimate of sandstone in proterozoic intracratonic Kaladgi-Badami basin, southern India. The distributions of heavy minerals are more in lower conglomerate; at the depth of 162.35m, zircon is 9.01%, magnetite is 74.18% and ilmenite is 24.61%. The ZTR index is 97.02%. The lower part of the upper unit of core quartz arenite, at the depth of 70.55m shows the following distribution of heavy minerals; zircon 2.94%, magnetite 50.84% and ilmenite 35.71%. The ZTR index of the quartz arenite is 65.52%; moderately abundant heavy minerals are tourmaline, rutile, and garnet; less abundant mineral is zircon in the core. The clay deposits in the basal arenite unit starts from 187 to 171.45m. The X-ray diffraction patterns shows 75% of Illite at the depth of 187m and 181.4m, 40% of chlorite at the depth of 181.7m, 36.36% of monmorillonite and 25% of kaolinite at the depth of 183m but 36.36% at the depth of 177.1m. kaolinite peaks are identified only in two samples. The study reveals that intense weathering in humid climate was responsible for alteration of granitic source rocks in the formation of kaolinitic clays in an acidic environment. The ZTR index reflects that the Badami sediments have attained moderate to high mineralogical maturity. The inference made out of the assemblage of heavy minerals point out that the Badami sediments have been sourced mainly from granitic and metamorphic terrain with a broad drainage basin. In most sandstone and conglomerate, the average ZTR index is moderate but varies widely among samples; apparently local lithologic source area variations largely control these relatively unmodified heavy mineral assemblages.

Heavy Minerals for Junior Woodchucks

In the last two centuries, since the dawn of modern geology, heavy minerals have been used to investigate sediment provenance and for many other scientific or practical applications. Not always, however, with the correct approach. Difficulties are diverse, not just technical and related to the identification of tiny grains, but also procedural and conceptual. Even the definition of “heavy minerals” is elusive, and possibly impossible. Sampling is critical. In many environments (e.g., beaches), both absolute and relative heavy mineral abundances invariably increase or decrease locally to different degrees owing to hydraulic-sorting processes, so that samples close to "neutral composition" are hard to obtain. Several widely shared opinions are misleading. Choosing a narrow size-window for analysis leads to increased bias, not to increased accuracy or precision. Only point-counting provides real volume percentages, whereas grain-counting distorts results in favor of smaller minerals. This paper also briefly reviews the heavy mineral associations typically found in diverse plate-tectonic settings. A mineralogical assemblage, however, only reproduces the mineralogy of source rocks, which does not correlate univocally with the geodynamic setting in which those source rocks were formed and assembled. Moreover, it is affected by environmental bias, and by diagenetic bias on top in the case of ancient sandstones. One fruitful way to extract information on both provenance and sedimentological processes is to look for anomalies in mineralogical–textural relationships (e.g., denser minerals bigger than lower-density minerals; harder minerals better rounded than softer minerals; less durable minerals increasing with stratal age and stratigraphic depth). To minimize mistakes, it is necessary to invariably combine heavy mineral investigations with the petrographic analysis of bulk sand. Analysis of thin sections allows us to see also those source rocks that do not shed significant amounts of heavy minerals, such as limestone or granite, and helps us to assess heavy mineral concentration, the “outer” message carrying the key to decipher the “inner message” contained in the heavy mineral suite. The task becomes thorny indeed when dealing with samples with strong diagenetic overprint, which is, unfortunately, the case of most ancient sandstones. Diagenesis is the Moloch that devours all grains that are not chemically resistant, leaving a meager residue difficult or even impossible to interpret when diagenetic effects accumulate through multiple sedimentary cycles. We have conceived this friendly little handbook to help the student facing these problems, hoping that it may serve the purpose.

Trace and Rare Earth Elements chemistry of detrital garnets in the SE Alps and Outer Dinarides flysch basins: An important tool to better define the source areas of sandstones

Abstract Garnet is one of the most abundant heavy minerals present in the Cretaceous – Eocene flysch deposits of the Southeastern Alps and Outer Dinarides (Julian, Brkini and Istrian basins). About 300 detrital garnets from the Cretaceous-Eocene flysch deposits of the Southeastern Alps have been analysed by means of electron microprobe and LA-ICP-MS. In the Julian and Istrian basins, supplies are from amphibolite-facies rocks and mafic and ultramafic metamorphic rocks, while in the Brkini basin the latter are almost missing. Moreover, in the Julian and Istrian basins, supplies from skarns, very low-grade metabasites, or from ultra-high temperature metamorphosed calc-silicate granulites are present. Among these different groups, LA-ICP-MS analyses showed that trace element content can be very different in almandine-rich garnets from the different sources. In particular, the source that supplied the Julian Basin is significantly different from that of the Istrian Basin. From the Cretaceous to the Palaeocene the main supplies of Bi-type garnets derived from an area where feldspar-free garnet-bearing rocks were exposed. Successively, Bi-type garnets were supplied from an area where feldspar-garnet-bearing rocks were exposed. The presence of garnets from feldspar-free garnet-bearing rocks in the Brkini and Istrian basins can be ascribed to both recycling of material from the Julian Basin as well as direct input from the same areas that supplied the Julian Basin.

Studies on Geochemical and Heavy Mineral Characteristics of Sediments of Gosthani River Estuary

The present work deals with the geochemical and heavy mineral characteristics studies of sediments of Gosthani river estuary. The aim of study is to determine the provenance, establish the depositional environment and spatial variability of sediment. From the study it is found that the sediment of Gosthani river contains heavy minerals that consist of Rutile, Garnet, Sillimanite, Staurolite, Monazite, Zercon, Pyroxenes, Epidote, Amphiboles and Opaques minerals. The lesser abundant heavy minerals are amphiboles, zircon, monazite, rutile, staurolite, epidote. These heavy minerals indicate that the sediments were essentially derived from metamorphic provenance varying from medium to high grade and partly from crystalline igneous rocks. Well rounded monazites come from Eastern Ghats. This is based on the occurrence of monazite in pegmatite and charnockites of Eastern Ghats. The various characters of rutile and zircon suggest that each of these minerals has a multisource. According to geochemical studies settling of organic matter is highest in areas where deposition of fine grained sediment takes place. The organic carbon is often a good index for deciphering depositional environment.

Timing of arrival of the Danube to the Black Sea: Provenance of sediments from DSDP site 380/380A

AbstractEstimates for the timing of the arrival of Danube sediment to the Black Sea range from Messinian to Pleistocene; the river is currently the largest sediment contributor, supplying 88 MT/yr. We identify two changes in siltstone provenance‐sensitive heavy mineral abundances at DSDP site 380/380A in the southwest Black Sea. Comparison with modern river sediment compositions indicates that siltstones above 571.5 mbsf (metres below sea floor) were supplied by the Danube, while sediments below 651.0 m were sourced by other supply systems. Palaeo‐magnetic, 40Ar/39Ar and biostratigraphic data reveal that the influx of Danube‐supplied sediment to the southwest Black Sea began between 4.36 ± 0.19 Ma and 1 Ma ago (Zanclean–Calabrian). Our results provide an independent time constraint on palaeogeographic reconstructions of the Pannonian and Dacian basins, which acted as upstream sediment sinks, and suggest that significant volumes of Danube‐supplied sediment only started to reach the Black Sea at least 1 Ma after the Messinian Salinity Crisis (5.971–5.33 Ma) had ended.

Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.