The Witwatersrand pyrites and metamorphism

1983 ◽  
Vol 47 (345) ◽  
pp. 473-479 ◽  
Author(s):  
D. K. Hallbauer ◽  
K. von Gehlen
Keyword(s):  
Trace Element ◽  
Fluid Inclusions ◽  
Depositional Environment ◽  
Volcanic Rocks ◽  
Source Rocks ◽  
Fine Grained ◽  
Mineral Inclusions ◽  
Ore Minerals ◽  
Hand Specimen

AbstractEvidence obtained from morphological and extensive trace element studies, and from the examination of mineral and fluid inclusions in Witwatersrand pyrites, shows three major types of pyrite: (i) detrital pyrite (rounded pyrite crystals transported into the depositional environment); (ii) synsedimentary pyrite (round and rounded aggregates of fine-grained pyrite formed within the depositional environmen); and (iii) authigenic pyrite (newly crystallized and/or recrystallized pyrite formed after deposition). The detrital grains contain mineral inclusions such as biotite, feldspar, apatite, zircon, sphene, and various ore minerals, and fluid inclusions with daughter minerals. Most of the inclusions are incompatible with an origin by sulphidization. Recrystallized authigenic pyrite occurs in large quantities but only in horizons or localities which have been subjected to higher temperatures during the intrusion or extrusion of younger volcanic rocks. Important additional findings are the often substantial amounts of pyrite and small amounts of particles of gold found in Archaean granites (Hallbauer, 1982) as possible source rocks for the Witwatersrand detritus. Large differences in Ag and Hg content between homogeneous single gold grains within a hand specimen indicate a lack of metamorphic homogenization. The influence of metamorphism on the Witwatersrand pyrites can therefore be described as only slight and generally negligible.

Trace Element Geochemistry and Mineral Inclusions Constraints on the Petrogenesis of a Marble–Hosted Ruby Deposit in Yunnan Province, China

2021 ◽  
Author(s):  
Wenqing Huang ◽  
Pei Ni ◽  
Ting Shui ◽  
Junyi Pan ◽  
Mingsen Fan ◽  
...  
Keyword(s):  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Yunnan Province ◽  
Geographic Origin ◽  
Source Rocks ◽  
Trace Element Geochemistry ◽  
Mineral Inclusion ◽  
Element Geochemistry ◽  
Inductively Coupled ◽  
Mineral Inclusions

Abstract Primary rubies in the Ailao Shan of Yunnan Province, China, are found in three layers of marble. However, the origin and source rocks of placer rubies in the Yuanjiang area remains unclear. Trace element geochemistry and inclusion mineralogy within these materials can provide information on their petrogenesis and original source. Zircon, rutile, mica group minerals, titanite, and apatite group minerals were the main solid inclusions identified within the placer Yuanjiang rubies, along with other mineral inclusions such as pyrite, pyrrhotite, plagioclase group minerals, and scapolite group minerals. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) measurements showed that the placer rubies are characterized by average values of Mg (31 ppmw), Ti (97 ppmw), V (77 ppmw), Cr (3326 ppmw), Fe (71 ppmw), and Ga (66ppmw). A trace-element oxide diagram, Fe values (<350 ppmw), and the mineral inclusion assemblage suggest marble sources for the placer ruby. Therefore, the Yuanjiang rubies (both primary and placer) are metamorphic, and this fits well with the observations that skarn and related minerals are mostly absent in this deposit. Yuanjiang rubies can be readily separated from the high-iron rubies of different geological types by their Fe content (<1000 ppmw). The discriminators Mg, Ga, Cr, V, Fe, and Ti have potential in separating Yuanjiang rubies from some other marble-hosted deposits, such as Snezhnoe. Nevertheless, geographic origin determination remains a challenge when considering the similarities in compositional features between the Yuanjiang rubies and rubies from some other marble-hosted deposits worldwide (e.g., Luc Yen). The presence of kaolinite group minerals and clusters of euhedral, prismatic zircon crystals in ruby suggest a Yuanjiang origin.

scholarly journals Pyrite Textures, Trace Elements and Sulfur Isotope Chemistry of Bijaigarh Shales, Vindhyan Basin, India and Their Implications

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 588
Author(s):  
Indrani Mukherjee ◽  
Mihir Deb ◽  
Ross R. Large ◽  
Jacqueline Halpin ◽  
Sebastien Meffre ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Sulfur Isotope ◽  
Volcanic Rocks ◽  
Central India ◽  
High Energy ◽  
Vindhyan Basin ◽  
Mean Values ◽  
Fine Grained ◽  
Sedimentary Pyrite

The Vindhyan Basin in central India preserves a thick (~5 km) sequence of sedimentary and lesser volcanic rocks that provide a valuable archive of a part of the Proterozoic (~1800–900 Ma) in India. Here, we present an analysis of key sedimentary pyrite textures and their trace element and sulfur isotope compositions in the Bijaigarh Shale (1210 ± 52 Ma) in the Vindhyan Supergroup, using reflected light microscopy, LA-ICP-MS and SHRIMP-SI, respectively. A variety of sedimentary pyrite textures (fine-grained disseminated to aggregates, framboids, lags, and possibly microbial pyrite textures) are observed reflecting quiet and strongly anoxic water column conditions punctuated by occasional high-energy events (storm incursions). Key redox sensitive or sensitive to oxidative weathering trace elements (Co, Ni, Zn, Mo, Se) and ratios of (Se/Co, Mo/Co, Zn/Co) measured in sedimentary pyrites from the Bijaigarh Shale are used to infer atmospheric redox conditions during its deposition. Most trace elements are depleted relative to Proterozoic mean values. Sulfur isotope compositions of pyrite, measured using SHRIMP-SI, show an increase in δ34S as we move up stratigraphy with positive δ34S values ranging from 5.9‰ (lower) to 26.08‰ (upper). We propose limited sulphate supply caused the pyrites to incorporate the heavier isotope. Overall, we interpret these low trace element signatures and heavy sulfur isotope compositions to indicate relatively suppressed oxidative weathering on land during the deposition of the Bijaigarh Shale.

scholarly journals Texture, mineralogy and geochemistry of Teri sediments from the Kuthiraimozhi deposit, Southern Tamilnadu, India: implications on provenance, weathering and palaeoclimate

2021 ◽  
Vol 14 (5) ◽  
Author(s):  
Udayanapillai Alagaiah Venu ◽  
Perumal Velmayil
Keyword(s):  
Tamil Nadu ◽  
Depositional Environment ◽  
Sand Dune ◽  
Coastal Region ◽  
Source Area ◽  
Source Rocks ◽  
High Status ◽  
Climate Conditions ◽  
Fine Grained ◽  
High Maturity

AbstractThe study examines about the red sand dune deposit locally designated as teri deposits; it is an omnipresent geomorphologic feature present in the coastal region of Thoothukudi and Ramanathapuram districts of Tamil Nadu, India. One of the inland teri sand dune outcrops is located around the Kuthiraimozhi village of Thoothukudi district in Tamil Nadu, India. Textural, mineralogical and geochemical studies were carried out in the teri sediments and its compact sandstone outcrops. The sediments are moderately sorted to well-sorted and finely skewed nature which indicates that fluvio-marine depositional environment. Geochemical analysis results of major, trace and rare earth elements for teri deposits help to predict the provenance, weathering status, depositional environment and climate. The geochemical study reveals that the sediments were derived from marine and non-marine sources. Teri sediments are geochemically classified as lithic arenite or wacke. Petrography and X-ray diffraction analysis reveal the predominance of quartz and feldspars along with the accessory minerals like ilmenite, rutile, garnet, magnetite, hematite, zircon, diopside, hypersthenes and biotite. Mineralogical observation illustrates that the teri sediments have originated from the weathering of felsic and mafic source rocks. The Chemical Index of Alteration (CIA) values of sediments represent moderate to the high status of weathering conditions in the source area. The depositional environment indicates that the sediments are fine-grained with high maturity index. Despite that the sediments are formed by fluvio-marine sources, the reddening character in the teri deposits is due to oxidation and leaching of iron-bearing minerals by percolating surface water from high rainfall and groundwater fluctuation of the aquifer under arid and semi-arid climate conditions.

scholarly journals Oligocene-Pleistocene Paleogeography within Banyumas Basin and implication to petroleum potential

2018 ◽  
Vol 1 ◽  
pp. 00006 ◽  
Author(s):  
Eko Bayu Purwasatriya ◽  
Sugeng Sapto Surjono ◽  
Donatus Hendra Amijaya
Keyword(s):  
Depositional Environment ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Magmatic Arc ◽  
The North ◽  
Potential Source ◽  
Back Arc ◽  
Exploration Activity

<p>This study attempts to reconstruct paleogeography of Banyumas Basin in association with magmatic arc evolution and its implication to petroleum potential. Based on the volcanic rocks distribution, their association and relatives age, there are three alignments of a magmatic arc, that are: (1) Oligo-Miocene arc in the south (2) Mio-Pliocene arc in the middle (3) Plio-Pleistocene arc in the north. The consequences of the magmatic arc movement were tectonic setting changing during Oligocene to Pleistocene, as well as their paleogeography. During Oligo-Miocene where magmatic arc existed in the southern part, the Banyumas tectonic setting was a back-arc basin. This tectonic setting was changing to intra-arc basin during Mio-Pliocene and subsequently to fore-arc basin since Plio-Pleistocene until today. Back-arc basin is the most suitable paleogeography to create a depositional environment for potential source rocks. Exploration activity to prove the existence of source rocks during Oligo-Miocene is needed to reveal petroleum potential in Banyumas Basin.<br></p>

Provenance and depositional environment of organic-rich calcareous black shale of the Late Ordovician Macasty Formation, western Anticosti Basin, eastern Canada

2019 ◽  
Vol 56 (3) ◽  
pp. 321-334 ◽  
Author(s):  
Keiko Hattori ◽  
André Desrochers ◽  
Janice Pedro
Keyword(s):  
Depositional Environment ◽  
Pore Space ◽  
Bulk Composition ◽  
Explosive Volcanism ◽  
Late Ordovician ◽  
Source Rocks ◽  
Eastern Canada ◽  
Fine Grained ◽  
Taconic Orogeny ◽  
Calcite Cement

The organic-rich Macasty shale in the Gulf of St. Lawrence was deposited in the Late Ordovician during the Taconic orogeny. The orogeny involved explosive volcanism and thrusting of allochthonous rocks in the eastern margin of North America. Neodymium isotope compositions of the shale show that the provenance is predominantly Grenvillian granite–gneissic rocks, which were widely exposed north of the basin, with little contribution from Taconic igneous rocks. The bulk composition and the presence of detrital kaolinite suggest that the Grenvillian source rocks underwent intense weathering before erosion. Fine-grained detritus was deposited in the Anticosti Basin, where abundant organic activity kept the sediment–water interface under anoxic conditions. This proposed interpretation is supported by the enrichment of redox-sensitive elements, such as As, V, and U, and by high δ34S for pyrite. Calcite cement formed in the pore space of sediments during the diagenesis at temperatures below 60 °C. The low-temperature diagenetic conditions are consistent with the preservation of abundant organic matter in the shale.

scholarly journals Depositional environment of Paleogen amber-bearing quartz-glauconite sands from Zdolbuniv (Rivne region, NW Ukraine): mineralogical and petrological evidences

2017 ◽  
Vol 33 (4) ◽  
pp. 45-62
Author(s):  
Lucyna Natkaniec-Nowak ◽  
Magdalena Dumańska-Słowik ◽  
Beata Naglik ◽  
Viktor Melnychuk ◽  
Мariya B. Krynickaya ◽  
...  
Keyword(s):  
Depositional Environment ◽  
Baltic Amber ◽  
Metamorphic Rocks ◽  
Bottom Part ◽  
Fine Grained ◽  
Clastic Rocks ◽  
Sedimentation Basin ◽  
Ore Minerals ◽  
Quartz Grains ◽  
Fossil Resins

Abstract Amber-bearing sands from Zdolbuniv mine are Paleogene fine-grained (0.6-0.12 mm) clastic rocks. The material is poorly rounded and moderately sorted out. It mainly consists of quartz, glauconite, and subordinately, feldspars (K-feldspars and plagioclases), mica, carbonates, zircon, epidote,fossil resins (Baltic amber) and ore minerals such as hematite, rutile, anatase, ilmenite. The presence of glauconite in the sands proves that sedimentation basin had to be marine reservoir. The variable composition of individual glauconite grains suggests the environmental conditions had to change during the sedimentation of clastic rocks. The occurrence of minerals, assembly such as zircon, epidote, ilmenite, rutile, anatase in the sands as well as the brown CL color of quartz grains, may suggest that majority of clastic material originated from metamorphic rocks, most probably coming from the Ukrainian Shield. Together with metamorphic material the fragment of fossil resins, i.e. Baltic amber, from the Paleogene off-shore forests could be transported to the sedimentation basin. Nowadays the bottom part of the analyzed profile is the most promising for the recovery of glauconite, whereas the exploration of Baltic amber may be initiated from the top of the profile.

scholarly journals The Niederschlag fluorite-(barite) deposit, Erzgebirge/Germany—a fluid inclusion and trace element study

2021 ◽  
Author(s):  
Sebastian Haschke ◽  
Jens Gutzmer ◽  
Cora C. Wohlgemuth-Ueberwasser ◽  
Dennis Kraemer ◽  
Mathias Burisch
Keyword(s):  
Fluid Inclusion ◽  
Trace Element ◽  
Fluid Inclusions ◽  
Open Space ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Fine Grained ◽  
Trace Element Study ◽  
Northern Atlantic ◽  
Homogenization Temperatures

AbstractThe Niederschlag fluorite-barite vein deposit in the Western Erzgebirge, Germany, has been actively mined since 2013. We present the results of a first comprehensive study of the mineralogy, petrography, fluid inclusions, and trace element geochemistry of fluorite related to the Niederschlag deposit. Two different stages of fluorite mineralization are recognized. Stage I fluorite is older, fine-grained, associated with quartz, and forms complex breccia and replacement textures. Conversely, the younger Stage II fluorite is accompanied by barite and often occurs as banded and coarse crystalline open-space infill. Fluid inclusion and REY systematics are distinctly different for these two fluorite stages. Fluid inclusions in fluorite I reveal the presence of a low to medium saline (7–20% eq. w (NaCl+CaCl2)) fluid with homogenization temperatures of 140–180 °C, whereas fluorite II inclusions yield distinctly lower (80–120 °C) homogenization temperatures with at least two high salinity fluids involved (18–27% eq. w (NaCl+CaCl2)). In the absence of geochronological data, the genesis of the earlier generation of fluorite-quartz mineralization remains enigmatic but is tentatively related to Permian magmatism in the Erzgebirge. The younger fluorite-barite mineralization, on the other hand, has similarities to many fluorite-barite-Pb-Zn-Cu vein deposits in Europe that are widely accepted to be related to the Mesozoic opening of the northern Atlantic Ocean.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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