scholarly journals Petrology and mineralogy of the Ulaan Del Zr-Nb-REE deposit, Lake Zone, Western Mongolia

2020 ◽  
Vol 50 ◽  
pp. 45-62
Author(s):  
Sanjsuren Oyunbat
Keyword(s):  
Fine Grained ◽  
Late Cambrian ◽  
Hydrothermal Processes ◽  
Western Mongolia ◽  
Lake Zone ◽  
High K ◽  
Ore Minerals ◽  
Type Granite ◽  
Host Rocks ◽  
Syenite Porphyry

The Ulaan Del deposit is located in the Lake Zone, Western Mongolia. In the area, middle-late Devonian alkali dykes of the Khalzan Complex are hosted in the middle-late Cambrian granodiorite-tonalite of the Togthohiinshil Complex. The alkali dykes of the Khalzan complex comprise medium- to fine-grained syenite, microsyenite, syenite-porphyry and trachyte, trachyrhyolite, and trachyandesite. The dykes are replaced to silica, sericite, albite, fluorite and are brecciated. They crosscut by quartz and quartz-carbonate veinlets. The dykes contain zircon (>0.19% Zr) with a total of rare earth elements oxides >0.1%. The host rocks of the Togtokhiinshil complex are mid-K, metaluminous, I- type granite, depleted in HFSE. Based on geochemical and mineralogical data, economic REE mineralization is concentrated in syenite and syenite porphyry of calc-alkaline high K to shoshonite series of A- type granite, emplaced at within a plate setting. Syenite dykes are enriched in REE. Ore minerals are zircon, apatite, sphene, monazite, xenotime, synchysite, parisite, fluorite and REE complex minerals, pyrite, rutile and limonite. Magmatic, metasomatic and hydrothermal processes significantly contributed to the formation of Zr, Nb, REE and Y mineralization at the Ulaan Del deposit.

scholarly journals Petrographical, petrochemical characteristics of Hòn Rồng massif granitoids, Cam Ranh, Khánh Hòa

2020 ◽  
Vol 3 (3) ◽  
pp. 195-212
Author(s):  
Nguyen Kim Hoang ◽  
Lam Van Phuong
Keyword(s):  
Biotite Granite ◽  
Accessory Mineral ◽  
Chemical Compositions ◽  
Phase 2 ◽  
Phase 3 ◽  
Fine Grained ◽  
South Vietnam ◽  
High K ◽  
Ore Minerals ◽  
Absolute Height

Hòn Rồng massif granitoid has a high mountainous terrain, with an absolute height of 728 m, relatively equal, slightly extended in the Northwest-Southeast direction, occupying an area of ​​about 29 km2. Petrographical composition is mainly medium - grained biotite granite (phase 2), minor is fine- grained biotite granite (phase 3), vein rocks are aplite granite and pegmatite and  a little of xenolith of granodiorite in medium - grained biotite granite. Medium-grained biotite granite: major mineral composition (%): plagioclase (oligoclase) 25–35, quartz 30, orthoclas 25, biotite 5 - 8 and few hornblend; fine-grained granite (%): plagioclase (oligoclase) 30 - 35; quartz 30 - 35; feldspar kali (orthoclase, and microclin) 30, biotite 3 - 5; accessory mineral is zircon, orthite, apatite, sphen, and very little ore minerals (about ​​2%); epimagmatic minerals including: chlorite, epidot, kaolinite, sericite, carbonate, sausorite-replaced association. Rocks are altered alkalization strongly (albitization and microlinization), and minor are chloritization, epidotization and sericitization. Averaged chemical compositions (%)SiO2: 69.07–72.07; total alkali(K2O+Na2O) 7.35–7.96. Ratio of K2O/Na2O 1.04, low TiO2 (0.24–0.37). Ratios of A/CNK 1.02–1.09, Rb/Sr: 0.27–1.62; Ba/Sr: 1.82–2.56, Ba/Rb: 1.58–7.13; K/Rb: 0.42–0.62; Ca/Sr: 0.21–0.47; the value of Eu anomalies is low. Granite belongs to calc-alkaline, aluminum content is from medium to high; K-Na alkaline series, I-granite type. Granitoid had been formed in plutonic - volcanic arc of subduction-zone. Compared with the granitoid formations in South Vietnam territory, Hòn Rồng massif granitoid belongs to phase 2 (main) and phase 3 (minor) of Đèo Cả complex with late Kreta age.

scholarly journals Petrography and Geochemical Characterization of a Granite Batholith in Idanre, Southwestern Nigeria

2021 ◽  
Vol 50 (2) ◽  
pp. 315-326
Author(s):  
Oluwatoyin O. Akinola ◽  
Azman A. Ghani ◽  
Elvaene James
Keyword(s):  
Calc Alkaline ◽  
Southwestern Nigeria ◽  
Geochemical Characterization ◽  
Fine Grained ◽  
Rock Types ◽  
Pan African ◽  
High K ◽  
Granite Batholith ◽  
Type Granite

Idanre granite batholith in southwestern Nigeria contain three rock types, namely, Older granite undifferentiated (OGu), Older granite porphyritic (OGp) and Older granite fine-grained (OGf). The granitoids intruded into a basement rock of primarily migmatite gneiss. Petrography indicates that quartz, orthoclase, hornblende, and biotite are common to all members while microcline is more prominent in OGp and plagioclase is poorly represented in OGf. Despite minor differences in petrographic features, the granite units generally have similar geochemical relationships. The average SiO2 contents in OGp (70.49%), OGu (68.7%) and OGf (65.8%) are comparable to similar Pan-African suites located in eastern and northern Nigeria. Na2O+K2O-CaO versus SiO2 diagram shows all the granite members are calcic, K2O vs SiO2 plot classify the granites as high-K calcic alkali to shoshonitic. ANK vs ACNK plot indicatesthey are peraluminous. Plot of A/CNK vs SiO2 and K2O vs Na2O diagrams classified the rock as S-type granite. The granitoids are calc-alkaline with elevated Na2O (>2.6%) and Al/(Na2O+CaO) contents (OGu, 2.1-3.4; OGp, 2.4-3.1 and OGf, 2.2-2.9). The tectonic diagram (Rb vs (Y+Nb) indicatesthatthe batholith is Within Plate Granite (WPG.

scholarly journals Magmatic Evolution and Compositional Characteristics of Tertiary Volcanic Rocks Associated with the Venarch Manganese Mineralization, Sw Qom, Central Iran

2015 ◽  
Vol 19 (2) ◽  
pp. 141-145 ◽  
Author(s):  
Mansoureh Mahdavi ◽  
Rahim Dabiri ◽  
Elham Shah Hosseini
Keyword(s):  
Subduction Zones ◽  
Volcanic Rocks ◽  
Ore Deposits ◽  
Geochemical Data ◽  
Magmatic Arc ◽  
High K ◽  
Ore Minerals ◽  
Manganese Mineralization ◽  
Host Rocks ◽  
Mn Ore

<p>The manganese (Mn) deposits of Iran date from late Proterozoic to Pliocene but the major high-grade Mn ore deposits are associated with tertiary basic to intermediate volcanic rocks. The Venarch Mn deposit is located in the SW Qom city and considered as one of the largest in Iran. The Mn mineralization is mostly hosted by Eocene high-k volcanic and pyroclastic rocks of Urmia-Dokhtar Magmatic Arc (UDMA). The study area mainly consists of basalt, trachybasalt, andesite, and basaltic-andesite that are intruded by Eocene-Oligocene monzodiorite, monzonite, and granodiorite intrusions. The Venarch Mn ore bodies are mostly hosted by shale beds and wrapped by altered mega-porphyritic andesites and spilitic lavas both in the foot and hanging walls. Petrographic studies show that the principal ore minerals are pyrolusite, psilomelane, and other Mn-oxides,and quartz and calcite were determined as the gang minerals. Integration of field geology, petrography, and geochemical results suggest a hydrothermal origin for the Venarch Mn deposit. Our geochemical data furthermore suggest the volcanic host rocks to be comparable to high-K series of subduction zones.</p><p> </p><p><strong>Evolución Magmática y Características de Composición en Rocas Volcánicas Terciarias Asociadas con la Mineralización de Manganeso en la Mina de Venarch, al Suroeste de Qom, en la Región Central de Irán</strong></p><p> </p><p><strong>Resumen</strong></p>Los yacimientos de manganeso (Mn) en Irán datan del Proterozoico tardío hasta el Plioceno, pero el mayor grado de los depósitos de la mena de manganeso se asocian a rocas volcánicas básicas a intermedias de edad Terciaria. El yacimiento de manganeso en la mina de Venarch se localiza al suroeste de la ciudad de Qom y está considerado como uno de los más grandes de Irán. La mineralización de manganeso se presenta en su mayoría en las rocas piroclásticas y volcánicas de alto contenido de K del Eoceno en el Arco Magmático Urmia-Dokhtar (UDMA, en inglés). El área de estudio presenta basaltos, traquibasaltos, andesitas y andesitas basálticas que están intruidas por monzodioritas, monzonitas y granodioritas del Eoceno-Oligoceno. Los cuerpos de mineral de manganeso en Venarch en su mayoría están dentro de capas de pizarra y envueltos por lavas espiliticas y andesitas megaporfiroides tanto en las paredes del piso como en las colgantes. Los estudios petrográficos muestran que los minerales son pirolusitas, silomelanas y otros óxidos de manganeso, mientras que los cuarzos y las calcitas constituyen los minerales de ganga. La integración de los trabajos de geología de campo, petrográficos y geoquímicos sugieren un origen hidrotérmal del yacimiento de manganeso de Venarch. Los datos geoquímicos de este estudio también sugieren que la roca volcánica anfitriona es comparable con las series ricas en K de las zonas de subducción.</p>

Mineralization of the South Pennine Orefield, UK—A Review

2016 ◽  
Vol 61 (1) ◽  
pp. 55-86 ◽  
Author(s):  
T.D. Ford ◽  
N.E. Worley
Keyword(s):  
Wall Rock ◽  
Hydraulic Gradient ◽  
Mississippi Valley ◽  
The South ◽  
The North ◽  
East Midlands ◽  
Ore Minerals ◽  
Placer Deposits ◽  
Fractured Limestone ◽  
Host Rocks

This review of the South Pennine Orefield (SPO) draws together the findings from many years of underground field observations and petrographical study. Mineralization is of the Mississippi Valley-type (MVT) and is concentrated within an area of some 200 km2, mainly along the eastern margins of a large inlier, the Derbyshire High, in Carboniferous platform carbonate host rocks. The inlier covers some 390 km2, forms an up-dip promontory of a larger structure, the East Midlands Shelf, and is surrounded by shales and sandstones of the Millstone Grit and Pennine Coal Measures groups. Mineralization probably began during the late Westphalian (Moscovian, Mid Pennsylvanian), when subsidence due to thermal sag resulted in the limestone being buried to depths of c. 4 km beneath younger strata. A palaeohydraulic reconstruction is presented from analysis of mineralized palaeokarst features, which are interpreted as representing hypogenic or deep-seated karst formed by the interstratal circulation of hydrothermal water in a mostly confined hydrodynamic setting. It is reasoned that Variscan inversion of N–S faults to the east of the SPO resulted in erosion of Namurian and Westphalian (Upper Mississippian–Middle Pennsylvanian) rocks and created a hydraulic gradient inclined towards the south-west. Acidic F-Ba-Pb-Zn enriched fluid evolved in the Namurian basinal rocks and migrated into fractured limestone. The resultant wall-rock dissolution along existing wrench faults led to the formation of a maze of stratiform mineral deposits (flats) and more irregular spongework-shaped structures (pipes). The presence of hydrocarbon accumulations in the limestones and evidence from fluid inclusions indicates that the mineralizing fluids were chloride/fluoride-rich and compositionally typical of oilfield brine. Isotope evidence demonstrates a sulphate evaporite source of sulphur, mainly from the Chadian (Visean, Middle Mississippian) Middleton Anhydrite Formation. By the late Cenozoic, karstification of exposed carbonate rocks began and the current pattern of epigenic karst drainage started to develop as the regional hydraulic gradient reversed, assuming its present eastward inclined attitude. The mineralized hypogenic karst was overprinted by later drainage systems as the hydraulic gradient changed, and placer deposits were formed from the erosion of existing mineralization. This was accompanied by circulation of meteoric water and resulted in the supergene weathering of the sulphide ore minerals. Eastward underflow of meteoric groundwater also exploited the same mineralization flow paths. There is evidence that pre-mineralization hypogenic karst was also significant in the formation of orebodies in the North Pennine Orefield and the Halkyn–Minera Orefield of NE Wales.

scholarly journals Petrogenesis and Metallogenic Implications of Neoproterozoic Granodiorite in the Super-Large Shimensi Tungsten-Copper Deposit in Northern Jiangxi, South China

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 429 ◽  
Author(s):  
Wenfeng Wei ◽  
Chunkit Lai ◽  
Bing Yan ◽  
Xiaoxi Zhu ◽  
Shengqiong Song ◽  
...  
Keyword(s):  
South China ◽  
Copper Deposit ◽  
High Background ◽  
Granite Emplacement ◽  
High K ◽  
P Content ◽  
Continental Arc ◽  
Type Granite ◽  
Ree Patterns ◽  
Type Classification

The newly discovered Shimensi deposit is a super-large tungsten-copper (W–Cu) deposit with a metal reserve of 742.55 thousand tonnes (kt) W and 403.6 kt Cu. The orebodies are hosted in Mesozoic granites, which intruded the poorly documented Shimensi granodiorite belonging to the Jiuling batholith, the largest intrusion (outcrop > 2500 km2) in South China. Our new SHRIMP (Sensitive High Resolution Ion MicroProbe) zircon dating revealed that the granodiorite at Shimensi (ca. 830–827 Ma) was formed coeval (within analytical uncertainty) or slightly earlier than those in many other places (ca. 819–807 Ma) of the Jiuling batholith. The Neoproterozoic Shimensi granodiorite is peraluminous and high-K calc-alkaline, and contains low P content with no S-type trend (positive P2O5 vs. SiO2 correlation) displayed, thus best classified as peraluminous I-type. The I-type classification is also supported by the zircon REE patterns, largely (93%) positive εHf(t) (−0.87 to 6.60) and relatively low δ18O (5.8–7.7‰). The Neoproterozoic Shimensi granodiorite was formed after the continental arc magmatism (ca. 845–835 Ma), but before the post-collisional S-type granite emplacement (ca. 825–815 Ma) in the Jiangnan Orogen. Therefore, we propose that the Shimensi granodiorite was formed in a collisional/early post-collisional setting. The δ18O increase from the Shimensi granodiorite to many younger (ca. 819–807 Ma) granodiorites (6.0–8.5‰) in the Jiuling batholith probably reflects an increase of supracrustal rock-derived melts with the progress of collision. The Shimensi granodiorite contains low zircon Ce4+/Ce3+ and Eu/Eu*, suggesting a relatively reducing magma that does not favor porphyry Cu–Au mineralization. This left a high background Cu concentration (avg. 196 ppm) in the Neoproterozoic granodiorite, which may have contributed to the Mesozoic W–Cu mineralization, when the granodiorite is intruded and assimilated by the Mesozoic granites.

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.

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