Pegmatites and aplites: Their genetic and applied ore geology

Dill, Harald G.

doi:10.1016/j.oregeorev.2015.02.022

Cited by 137 publications

(57 citation statements)

References 266 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Renewed interest in biotite pegmatites has arisen due to their economic U endowment [2][3][4][5]. The most important U hosts in pegmatite-type U deposits are uraninite and coffinite, common minerals containing reduced U 4+ found in nature [6][7][8]. Self-oxidation caused by radioactive decay of U, and valence compensation due to prevalent cationic substitutions have collectively contributed to the coexistence of mixed U 4+ and U 6+ in uraninite and coffinite structure [9,10].…”

Section: Introductionmentioning

confidence: 99%

Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China

et al. 2019

View full text Add to dashboard Cite

The biotite pegmatites in the Shangdan domain of the North Qinling orogenic belt contain economic concentrations of U, constituting a low-grade, large-tonnage pegmatite-hosted uraniferous province. Uraninite is predominant and ubiquitous ore mineral and coffinite is common alteration mineral after initial deposit formation. A comprehensive survey of the uraninite and coffinite assemblage of the Chenjiazhuang, Xiaohuacha, and Guangshigou biotite pegmatites in this uraniferous province reveal the primary magmatic U mineralization and its response during subsequent hydrothermal events. Integrating the ID-TIMS (Isotope Dilution Thermal Ionization Mass Spectrometry) 206 Pb/ 238 U ages and U-Th-Pb chemical ages for the uraninites with those reported from previous studies suggests that the timing of U mineralization in the uraniferous province was constrained at 407-415 Ma, confirming an Early Devonian magmatic ore-forming event. Based on microtextural relationships and compositional variation, three generations of uranium minerals can be identified: uaninite-A (high Th-low U-variable Y group), uranite-B (low Th-high U, Y group), and coffinite (high Si, Ca-low U, Pb group). Petrographic and microanalytical observations support a three-stage evolution model of uranium minerals from primary to subsequent generations as follows: (1) during the Early Devonian (stage 1), U derived from the hydrous silicate melt was mainly concentrated in primary magmatic uaninite-A by high-T (450-607 • C) precipitation; (2) during the Late Devonian (stage 2), U was mobilized and dissolved from pre-existing uraninite-A by U-bearing fluids and in situ reprecipitated as uraninite-B under reduced conditions. The in situ transformation of primary uraninite-A to second uraninite-B represent a local medium-T (250-450 • C) hydrothermal U-event; and (3) during the later low-T (100-140 • C) hydrothermal alteration (stage 3), U was remobilized and derived from the dissolution of pre-existing uraninite by CO 2 -and SiO 2 -rich fluids and interacted with reducing agent (e.g., pyrite) leading to reprecipitation of coffinite. This process represents a regional and extensive low-T hydrothermal U-event. In view of this, U minerals evolved from magmatic uraninite-A though fluid-induced recrystallized uraninite-B to coffinite, revealing three episodes of U circulation in the magmatic-hydrothermal system.

show abstract

Section: Introductionmentioning

confidence: 99%

Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Fractionation of Nb vs. Ta is commonly observed [3,[36][37][38], with Nb usually highly concentrated in peralkaline granites [39] when Ta is mostly concentrated in peraluminous leucogranites and pegmatites [3,4,22,39,40]. The behaviour of the Nb and Ta elements drastically changes depending on melt composition and/or fluxing elements, like F, Li, P, and B [3,11,38,[41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Evidence for Nb-Ta Occurrences in the Syn-Tectonic Pan-African Mayo Salah Leucogranite (Northern Cameroon): Constraints from Nb-Ta Oxide Mineralogy, Geochemistry and U-Pb LA-ICP-MS Geochronology on Columbite and Monazite

et al. 2018

View full text Add to dashboard Cite

The Mayo Salah pluton, which is located in the North-Cameroon domain of Central African Bold Belt (CAFB), is emplaced as a laccolith in volcano-sedimentary schists of Poli series, and displays features of Rare-metal Granite (RMG). It is made of two main rock groups: (1) the metaluminous barren muscovite granite (MsG) and (2) the Nb-Ta bearing peraluminous leucogranite (MsL) which expresses four subtypes. The evolved Rare-element MsL is subalkaline, slightly peraluminous (ASI = 1.01-1.21), and it displays flat REE chondrite-normalized patterns with a strong negative Eu anomaly (Eu/Eu* = 0.02-0.20). It belongs to the peraluminous low phosphorus Rare-element Granites and L-type igneous rocks, as shown by the relatively low Zr/Hf (4.8-14) and Nb/Ta (1.4-9.0) ratios and the positive slope of the Zr-Hf-Nb-Ta profile in spider diagrams. The rare-element-bearing mineral is represented by columbite-group minerals (CGM) and other Nb-Ta-oxides (Nb-rutile and pyrochlore supergroup minerals). The CGM is classified as Mn-columbite, with Ta# and Mn# ratios increasing from core to rim. Two stages of mineralization are identified; the earliest stage (CGM-I) consists in scattered tabular or prismatic euhedral grains that were related to magmatic fractionation. The latest stage (CGM-II) is expressed as a Ta-rich Mn hydrothermal CGM episode represented as rims and/overgrowths around and/or as veinlet crosscutting CGM-I or in cleavage planes of muscovite. The U-Pb dating of columbite and monazite of the Mayo Salah leucogranite indicates a late-Neoproterozoic magmatic-hydrothermal mineralization event from 603.2 ± 5.3 to 581.6 ± 7.2 Ma, as consistent with both late D 2 to D 3 events that were recorded in the CAFB in Cameroon, and the associated continental collision environment. The Nb-Ta mineralization of the Mayo Salah pluton provides evidence for the presence of RMG in Northern Cameroon of CAFB, and its temporal association with the youngest period of metallogenic epoch of Nb-Ta-ore formation in Africa associated to Pan-African times. This paper presents an original geological description of the Mayo Salah leucogranite from the Poli region, North Cameroon ( Figure 2). It provides evidence for the first rare-metal bearing granite that is described in this area through field observations, whole-rock geochemistry, textural features, and Minerals 2018, 8, 188 5 of 36 mineralogy of Nb-Ta oxides-bearing minerals. Combining the geochemical and mineralogical features of the Mayo Salah leucogranite with U-Pb geochronological constraints on associated columbite and monazite minerals will allow for discussing the granite emplacement within the current knowledge of the geodynamic environment in this area during Pan-African times. Geological ContextThe Poli region belongs to the Northern Cameroon domain (NCD) of the Central Africa Fold Belt (CAFB) in Cameroon (Figure 2; [62 -64,67-70,79]). This domain results from the collision between the Sahara metacraton [80,81] and the Adamawa-Yadé domain (AYD). Precambrian terrains of the NCD are made of t...

show abstract

“…The regional zoning is also described in similar mineralogy, composition and texture with the above classification. Simple description as spodumene type for Kenticha rare metal pegmatite would not fit since it also consists of Li-silicates accommodated in lepidolite, spodumene, holmquistite, albite and swinfordite and Li-phosphates existed in the form of amblygonite and lithiophyllite [31]. Numerous veins and dikes in Kenticha show inward mineralogical and textural changes in an increasing in complexity parallel to the degree of pegmatite fractionation [29].…”

Section: Regional and Compositional Zoningsmentioning

confidence: 99%

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

Mohammedyasin¹

2017

IJG

View full text Add to dashboard Cite

This work reviews the geology, geochemistry and geochronology and discusses the spatial and temporal relationship of the granite pegmatite and the rare metal mineralization of the Kenticha granite pegmatite, southern Ethiopia using published and unpublished works to give a comprehensive understanding about the formation of the mineral deposit. The Kenticha rare metal pegmatite belt comprises several groups of pegmatites which show a high magmatic fractionation, regional and compositional zoning, mineralogical assemblage, and secondary alterations. The internal zonation shows high degree of evolution from the border to the core zone during crystallization and solidification of the leucogranitic to pegmatitic melt. Tantalum mineralization at Kenticha includes zoned tantalite-(Mn) and columbite-(Mn), as well as microlite, pyrochlore, uranmicrolite, and rare tapiolite, ixiolite/wodginite and Ta-bearing rutile. The tectonic setting of the Kenticha granite pegmatite in the Within Plate Granite (WPG) to syn-Collisional Granite (syn-COLG) suites and probably sourced from extreme fractionation of syn-to late tectonic granites or anatexis process of the metasedimentary rocks in the area. The emplacement of the Kenticha pegmatite was at ca. 530 Ma and temporally related to the post-collisional phase of granitic magmatism at 570 -520 Ma, after the last tectonic stage of east African orogeny during the late stage of Gondwana assembly.

show abstract

Pegmatites and aplites: Their genetic and applied ore geology

Cited by 137 publications

References 266 publications

Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China

Geochronology and Geochemistry of Uraninite and Coffinite: Insights into Ore-Forming Process in the Pegmatite-Hosted Uraniferous Province, North Qinling, Central China

Evidence for Nb-Ta Occurrences in the Syn-Tectonic Pan-African Mayo Salah Leucogranite (Northern Cameroon): Constraints from Nb-Ta Oxide Mineralogy, Geochemistry and U-Pb LA-ICP-MS Geochronology on Columbite and Monazite

Geology, Geochemistry and Geochronology of the Kenticha Rare Metal Granite Pegmatite, Adola Belt, Southern Ethiopia: A Review

Contact Info

Product

Resources

About