scholarly journals Kivilompolo Mo mineralization in the Peräpohja belt revisited: Trace element geochemistry and Re-Os dating of molybdenite

2020 ◽  
Vol 92 (2) ◽  
pp. 131-150
Author(s):  
Jukka-Pekka Ranta ◽  
◽  
Eero Hanski ◽  
Holly Stein ◽  
Matthew Goode ◽  
...  
Keyword(s):  
Uranium Mineralization ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Zircon Age ◽  
Porphyritic Granite ◽  
Quartz Veins ◽  
Nappe Complex ◽  
Magmatic Fluids

The Kivilompolo molybdenite occurrence is located in the northern part of the Peräpoh jabelt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The minerali-zation occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.

Mineralogy, geochemistry and petrogenesis of the V-Ti-bearing and chromiferous magnetite deposits hosted by Neoarchaean Channagiri Mafic-Ultramafic Complex, Western Dharwar Craton, India: Implications for emplacement in differentiated pulses

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Tadasore Devaraju ◽  
Kallada Jayaraj ◽  
Thavaraghatta Sudhakara ◽  
Tuomo Alapieti ◽  
Beate Spiering ◽  
...  
Keyword(s):  
Dharwar Craton ◽  
Coarse Grained ◽  
Trace Element Geochemistry ◽  
Second Phase ◽  
Element Geochemistry ◽  
Silicate Mineral ◽  
Interface Zone ◽  
Fine Grained ◽  
Ultramafic Complex ◽  
Late Stages

AbstractThe Channagiri Mafic-Ultramafic Complex occupies lowermost section of the Neoarchaean Shimoga supracrustal group in the Western Dharwar Craton. It is a segmented body occupying the interdomal troughs of granitoids. The magnetite deposits occur in the northeastern portion; typically occupying the interface zone between gabbro and anorthositic. Mineralogically, the deposits are simple with abundant magnetite and ilmenite. Hogbomite is a consistent minor mineral. Magnetites are typically vanadiferous (0.7–1.25% V2O5). Ilmenite consistently analyses more MgO and MnO than coexisting magnetite. Chlorite, almost the only silicate present; lies in the range of ripidolite, corundophilite and sheridanite. The chromiferous suit occupying eastern side of Hanumalapur block (HPB) contains Fe-Cr-oxide analysing 37.8–11.9% Cr2O3 and 40.5–80% FeOt. In these too, chlorite, typically chromiferous (0.6–1.2% Cr2O3), is the most dominant silicate mineral. Geochemistry of V-Ti-magnetite is dominated by Fe, Ti and V with Al, Si, Mg and Mn contributing most of the remaining. Cr, Ni, Zn, Co, Cu, Ga and Sc dominate trace element geochemistry. The Cr-magnetite is high in Cr2O3 and PGE. Two separate cycles of mafic magmatism are distinguished in the CMUC. The first phase of first cycle, viz., melagabbro-gabbro, emplaced in the southeastern portion, is devoid of magnetite deposits. The second phase, an evolved ferrogabbroic magma emplaced in differentiated pulses, occupying northeastern portion of the complex, consists of melagabbro→gabbro-anorthosite→V-Ti magnetite→ferrogabbro sequence. Increase in oxygen fugacity facilitated deposition of V-Ti magnetite from ferrogabbroic magma pulse emplaced in late stages. The second cycle of chromiferous PGE mineralized suite comprises fine-grained ultramafite→alternation of pyroxinite-picrite→Crmagnetite sequence formed from fractionation of ferropicritic magma. HPB also includes >65m thick sill-like dioritic phase at the base of the ferriferous suit and a sinuous band of coarse-grained ultramafite enclosed within the chromiferous suit; both unrelated to the two mafic magmatic cycles.

The Hudesheng mafic–ultramafic intrusions in the Oulongbuluke Block, Qinghai Province, NW China: chronology, geochemistry, isotopic systematics and tectonic implications

2018 ◽  
Vol 156 (9) ◽  
pp. 1527-1546 ◽  
Author(s):  
Haoran Li ◽  
Fengyue Sun ◽  
Liang Li ◽  
Jiaming Yan
Keyword(s):  
Crustal Contamination ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Field Observations ◽  
Element Geochemistry ◽  
Qinghai Province ◽  
Nw China ◽  
The North ◽  
Depleted Mantle ◽  
Regional Tectonic

AbstractThe Hudesheng mafic–ultramafic intrusions are located in the Oulongbuluke Block, north of the Qaidam Block in Qinghai Province, NW China. We carried out a detailed study of the intrusions, including field observations, petrology, zircon U–Pb geochronology, Lu–Hf isotopes, bulk-rock major- and trace-element geochemistry, and mineral compositions, to provide a better understanding of their properties and the regional tectonic evolution. Zircon U–Pb dating on gabbro and pyroxenite samples yielded ages of 465 and 455 Ma, respectively. Geochemical data, in conjunction with the field observations and petrological features, suggest that the complex is Alaskan-type and the magma was derived from a depleted mantle source that was hydrous picritic basalt in composition and influenced by crustal contamination and slab-derived fluid metasomatism. Based on all the chronological, petrological, mineralogical and geochemical and regional geological data, we conclude that the palaeo-ocean closed diachronously from west to east between the Qaidam and Oulongbuluke blocks, and that the ocean in the east of the North Qaidam region closed after ∼455 Ma.

Oxygen, carbon and strontium isotope study of the carbonatitic dolomite host of the Bayan Obo Fe-Nb-REE deposit, Inner Mongolia, N China

1997 ◽  
Vol 61 (407) ◽  
pp. 531-541 ◽  
Author(s):  
M. J. Le Bas ◽  
B. Spiro ◽  
Yang Xueming
Keyword(s):  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Fine Grained ◽  
Dolomite Marble ◽  
Ore Body ◽  
Ore Bodies ◽  
Isotope Study ◽  
Bayan Obo

AbstractThe large Fe-Nb-REE deposit at Bayan Obo is hosted by a dolomite marble within the thrust complex of marbles, quartzites and slates that belongs to the Bayan Obo Formation of mid-Proterozoic age. The dolomite is either a dolomitized sedimentary limestone subsequently mineralized and tectonically thrust and folded, or a dolomite (or dolomitized) carbonatite intrusion with late-stage recrystallization and mineralization that has been subsequently tectonically deformed.O and C isotope data indicate that the sedimentary limestones and dolomites of the Bayan Obo Formation, which occur in the thrust stack together with quartzites and slates, have values of δO c. +20 per mil (SMOW) and δC c. zero. In contrast, the coarser grained facies of the large (0.5 × 10 km) dolomite marble which hosts the REE ore body has δO per mil values between +8 and +12 and δC values between −5 and −3, whereas the finer-grained recrystallized and REE-mineralized dolomite marble which occurs close to the ore bodies has δO between +12 to +16 and δC between −4 and zero. 87Sr/86Sr data confirm this distinction: >0.710 for the sedimentary rocks and <0.704 for the coarse- and fine-grained dolomite marbles.These data are taken to indicate that the large and coarse-grained dolomite was an igneous carbonatite (as borne out by its fenitic contact rocks and trace element geochemistry), and that the finer grained dolomite recrystallized under the influence of mineralizing solutions which entrained groundwater. The stratiform features in the coarse-grained dolomite that are evident in the field are interpreted as tectonic layering.

scholarly journals Tectonochemistry of the Brooks Range Ophiolite, Alaska

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Joseph Biasi ◽  
Paul Asimow ◽  
Ronald Harris
Keyword(s):  
Continental Margin ◽  
Mineral Chemistry ◽  
The Arctic ◽  
Geochemical Data ◽  
New Mineral ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Brooks Range ◽  
Arctic Alaska ◽  
Intrusive Rocks

Abstract We present new whole-rock geochemical data from the Brooks Range ophiolite (BRO) together with new mineral chemistry data from the BRO, South Sandwich forearc, Izu-Bonin forearc, and Hess Deep. The analyses reveal that the Brooks Range ophiolite (BRO) was most likely created in a forearc setting. We show that this tectonic classification requires the Brookian orogeny to begin at ~163-169 Ma. The middle-Jurassic BRO contains abundant gabbros and other intrusive rocks that are geochemically similar to lithologies found in other forearc settings. Based on major, minor, and trace element geochemistry, we conclude that the BRO has clear signals of a subduction-related origin. High-precision olivine data from the BRO have a forearc signature, with possible geochemical input from a nearby arc. The Koyukuk terrane lies to the south of the Brooks Range; previous studies have concluded that the BRO is the forearc remnant of this arc-related terrane. These studies also conclude that collision between the Koyukuk Arc and the Arctic Alaska continental margin marks the beginning of the Brookian orogeny. Since the BRO is a forearc ophiolite, the collision between the Koyukuk Arc and the continental margin must have coincided with obduction of the BRO. Previously determined 40Ar/39Ar ages from the BRO’s metamorphic sole yield an obduction age of 163-169 Ma. Since the same collisional event that obducts the BRO also is responsible for the Brookian orogeny, we conclude that the BRO’s obduction age of ~163-169 Ma marks the beginning of this orogenic event.

scholarly journals Hydrotermálny bastnäsit-(Ce) zo štôlne Elisabeth pri Gemerskej Polome (Slovenská republika)

2020 ◽  
Vol 28 (1) ◽  
pp. 1-8
Author(s):  
Martin Števko ◽  
Jiří Sejkora ◽  
Zdeněk Dolníček
Keyword(s):  
Infrared Spectra ◽  
Rare Metal ◽  
Coarse Grained ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Quartz Veins ◽  
Hydrothermal Quartz ◽  
Magmatic Fluids ◽  
Type Granite ◽  
Pale Green

Bastnäsite-(Ce), ideally CeCO3F, was recently found at the dumps of the Elisabeth adit near Gemerská Poloma, Rožňava Co., Košice Region, eastern Slovakia. It forms orange-brown aggregates up to 2 × 1 cm with vitreous to greasy lustre, which occur in the hydrothermal quartz veins crosscutting the coarse-grained, porphyritic rare metal S-type granite. Bastnäsite-(Ce) is closely associated with white, pale-green to purple fluorite, siderite and minor pyrite. It is hexagonal, space group P-62c with refined unit-cell parameters: a 7.1354(1) Å, c 9.7954(2) Å and V 431.90(1) Å3. The empirical formula of bastnäsite-(Ce) from the Gemerská Poloma based on sum of all cations = 1 apfu is (Ce0.49 La0.22Nd0.15Pr0.05Sm0.03Th0.02Ca0.02Gd0.01Y0.01)Σ1.00(CO3)1.00F0.83(OH)0.17. The Raman and infrared spectra of bastnäsite-(Ce) as well as tentative assignment of observed bands are given in this paper. Bastnäsite-(Ce) and associated minerals were formed from the early-hydrothermal post-magmatic fluids related to the adjacent granite.

Provenance and depositional characteristics of Lathi Formation in southern part of Jaisalmer Basin: Implications for exploration of sandstone type uranium mineralization

2021 ◽  
Vol 38 (1) ◽  
pp. 41-50
Author(s):  
Shijo Mathew ◽  
Pritam Karmakar ◽  
Rajeev Bidwai ◽  
S K Sharma ◽  
Navin Goyal ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Gravity Data ◽  
Source Area ◽  
Sedimentary Facies ◽  
Climatic Conditions ◽  
Uranium Mineralization ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Carbonaceous Matter ◽  
Jaisalmer Basin

The lower Jurassic Lathi Formation covers about 900 sq. km area and forms the lowermost unit of Jaisalmer Basin of western Rajasthan. Lithologically the Lathi Formation comprises of conglomerate, sandstone, siltstone, shale and mudstone. The sandstones are generally medium- to coarse-grained, moderately sorted and show variation in colour, grain-size and texture. Petrographic studies indicate a mixed provenance for the Lathi sandstone. On the basis of geochemical data, theses sandstones are classified into sub-arkose, litharenite and sub-litharenite. Palaeo-weathering indices such as CIA (80.45), CIW (85.23) and PIA (84.23) suggest moderate to high degree of chemical weathering of the source area, intermediate and felsic igneous provenance, under humid to semi-humid climatic conditions. Further, the geochemical data indicate the sedimentation in a passive continental margin setting. The Bouguer gravity image clearly depicts the north westward slope of the basement. Modelling studies of the gravity data revealed average depth to the basement as 800m, 400m and 250m respectively in northwest, central and southeastern parts of the surveyed area. Exploration activities by Atomic Minerals Directorate for Exploration and Research have resulted in location of several uranium anomalies in the Lathi Formation. Lathi Formation is characterised by many favourable parameters such as fertile provenance, arkosic sandstones intercalated with shale/mudstone, reduced sedimentary facies with carbonaceous matter, lignite and pyrite deposited in continental to marginal marine environment. Malani Igneous Suit and metamorphic rocks constitute the basement for Jaisalmer Basin. Malani rhyolites and granites are fertile source of uranium, containing 6.7 ppm and 9.2 ppm average and intrinsic uranium respectively. Presence of carbonaceous matter and pyrite bearing sandstones, indicative of reducing environment at depth below water table (R.L. 150 m), was reported during subsurface exploration in Lathi sandstone which is a favourable condition for Lathi sediments to host uranium mineralization.

scholarly journals A survey of Sierra Nevada magmatism using Great Valley detrital zircon trace-element geochemistry: View from the forearc

Lithosphere ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 603-619
Author(s):  
Kathleen DeGraaff Surpless ◽  
Diane Clemens-Knott ◽  
Andrew P. Barth ◽  
Michelle Gevedon
Keyword(s):  
Trace Element ◽  
Sierra Nevada ◽  
Detrital Zircon ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Arc Magmatism ◽  
Forearc Basin ◽  
Element Geochemistry ◽  
Continental Arc ◽  
Great Valley

AbstractThe well-characterized Sierra Nevada magmatic arc offers an unparalleled opportunity to improve our understanding of continental arc magmatism, but present bedrock exposure provides an incomplete record that is dominated by Cretaceous plutons, making it challenging to decipher details of older magmatism and the dynamic interplay between plutonism and volcanism. Moreover, the forearc detrital record includes abundant zircon formed during apparent magmatic lulls, suggesting that understanding the long-term history of arc magmatism requires integrating plutonic, volcanic, and detrital records. We present trace-element geochemistry of detrital zircon grains from the Great Valley forearc basin to survey Sierra Nevadan arc magmatism through Mesozoic time. We analyzed 257 previously dated detrital zircon grains from seven sandstone samples of volcanogenic, arkosic, and mixed compositions deposited ca. 145–80 Ma along the length of the forearc basin. Detrital zircon trace-element geochemistry is largely consistent with continental arc derivation and shows similar geochemical ranges between samples, regardless of location along strike of the forearc basin, depositional age, or sandstone composition. Comparison of zircon trace-element data from the forearc, arc, and retroarc regions revealed geochemical asymmetry across the arc that was persistent through time and demonstrated that forearc and retroarc basins sampled different parts of the arc and therefore recorded different magmatic histories. In addition, we identified a minor group of Jurassic detrital zircon grains with oceanic geochemical signatures that may have provenance in the Coast Range ophiolite. Taken together, these results suggest that the forearc detrital zircon data set reveals information different from that gleaned from the arc itself and that zircon compositions can help to identify and differentiate geochemically distinct parts of continental arc systems. Our results highlight the importance of integrating multiple proxies to fully document arc magmatism, demonstrating that detrital zircon geochemical data can enhance understanding of a well-characterized arc, and these data may prove an effective means by which to survey an arc that is inaccessible and therefore poorly characterized.

scholarly journals Paleoproterozoic Adakitic Rocks in Qingchengzi District, Northeastern Jiao-Liao-Ji Belt: Implications for Petrogenesis and Tectonism

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 684
Author(s):  
Jian Li ◽  
Hanlun Liu ◽  
Keyong Wang ◽  
Wenyan Cai
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Biotite Granite ◽  
Granitic Rocks ◽  
Geochemical Data ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Magmatic Rocks

Herein, zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock major and trace element geochemistry are presented for two Palaeoproterozoic granitic rocks in Qingchengzi district, northeastern Jiao-Liao-Ji Belt (JLJB). These new geochronological and geochemical data provide reference clues for exploring the petrogenesis and tectonic setting of Paleoproterozoic magmatic rocks in the Qingchengzi district, which further constrain the tectonic nature of the JLJB. Our zircon U-Pb dating denotes that the Paleoproterozoic magmatic events in the Qingchengzi district were emplaced at ~2163 Ma and ~1854 Ma, represented by granite porphyry and biotite granite, respectively. Geochemically, these Palaeoproterozoic rocks are characterized by high Sr (760–842 ppm), SiO2 (69.72–70.89 wt.%), and Al2O3 (15.53–16.78 wt.%) contents, low Y (2.1–9.0 ppm) and Yb (0.25–0.80 ppm) contents, which indicate an adakite affinity. Combined with Hf isotopic composition (εHf(t) = −1.5~+4.8; TDM2 = 3109~2560 Ma), we believe that the Paleoproterozoic adakitic magma originated from partial melting of the thickened lower crust material in the Meso-Neoarchean. Moreover, these rocks are enriched in light rare earth elements and large ion lithophilic elements (e.g., K, Rb, and Cs), and depleted in heavy rare earth elements and high field strength elements (e.g., Nb and Ta). These features are similar to magmatic rocks formed in an arc environment (either island arc or active continental margin) and are not consistent with an intraplate/intracontinental environment. According to this study and previous research results, we conclude that the arc–continent collision model is conducive to the Paleoproterozoic tectonic attribute of the JLJB, and the oceanic crust subduction between the Namgrim and Longgang blocks may have induced the widespread occurrence of magmatic events in the region.

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