Differentiated rare-element mineralization in an ongonite–topazite composite dike at the Xianghualing tin district, Southern China: An electron-microprobe study on the evolution from niobium–tantalum-oxides to cassiterite

Huang, Fangfang; Wang, Rucheng; Xie, Lie‐Wen; Zhu, Junjiang; Erdmann, Saskia; Che, Xudong; Zhang, Rongqing

doi:10.1016/j.oregeorev.2014.08.008

Cited by 38 publications

(14 citation statements)

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“…In addition, fluids derived from mantle‐derived magmas underplated in the lower crust, which are inferred to have provided most of the heat for generating the crustal melts and Jurassic granites in South China (e.g., Li et al, , ; Zhao et al, ), could have played a role as well, though such fluids would have been CO 2 ‐rich, while we infer low CO 2 contents for the main granite magmas with X H 2 O > 0.7 during most of its crystallization (compare Figures and ). Based on the composition of the natural Bt crystals, melt fluorine contents appear to have been ~0.2 wt % and thus moderately high during Bt crystallization (using a ( D F Bt/melt ) partition coefficient of 3.7 according to Icenhower and London (), but significantly below saturation (at several wt %; Bailey, ; Huang et al, ) until late‐stage crystallization. The fact that experimental Amps also have similar F contents than their natural counterparts further shows that F content in the experiments was similar to that in the magma (Table S7).…”

Section: Discussionmentioning

confidence: 99%

Experimental Constraints on Intensive Crystallization Parameters and Fractionation in A‐Type Granites: A Case Study on the Qitianling Pluton, South China

et al. 2019

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Phase equilibrium experiments are essential for robustly and accurately constraining the intensive parameters of magma systems and their fractionation history, which is particularly true for A-type granites crystallized from H 2 O-rich melts and at reducing conditions. Here, we constrain the crystallization conditions of the ferroan (A-type), Sn-mineralized Qitianling granite of South China, which formed during a major event of crustal formation and reorganization in the Mesozoic. To characterize the magma system conditions and fractionation, we have carried out a series of experiments on three representative, amphibole-bearing samples. The experiments were performed at 100-700 MPa (mainly at 200 and 300 MPa), at an fO 2 of~NNO−1.3 (1.3 log unit below the Ni-NiO buffer) or~NNO+2.4, at 660 to 900°C , and at variable H 2 O melt (~3-9 wt %). They show that the Qitianling magmas last crystallized at ≥300-350 MPa, at a H 2 O melt ≥ 6.5-8.0 wt %, and that magmatic fO 2 was~NNO−1.3 ± 0.5 at above-solidus conditions. Amphibole texture in the rocks suggests an early crystallization of this mineral, hence that water-rich (≥4 wt % H 2 O in melt) conditions prevailed early during the magmatic evolution, prior to amphibole crystallization. At all investigated conditions, amphibole crystallization requires at least 5-6 wt % dissolved H 2 O, being even absent in the more potassic composition. We interpret this as resulting from the elevated K 2 O content of the investigated compositions that inhibits amphibole crystallization in metaluminous granitic systems. The experimental liquid line of descent obtained at 200-300 MPa mimics the geochemical trend expressed by the pluton suggesting that fractionation occurred in the upper crustal reservoir. Key Points: • A-type Qitianling magmas were produced at high temperature (>900°C ) and with initial H 2 O melt ≥ 4 wt % • Crystallization of Qitianling granites occurred at ≥300-350 MPa, NNO −1.3 ± 0.5, and near-solidus H 2 O melt ≥ 6.5-8.0 wt % • Fractionation of the magmas occurred at or close to the level of final emplacement and crystallization Supporting Information: • Supporting Information S1granite evolution, we have carried out phase equilibrium experiments to robustly constrain the intensive parameters of crystallization for the A-type granites. We present (1) a petrological and geochemical overview on the Qitianling pluton; and (2) results from our phase equilibrium experiments; followed by a discussion of (3) the intensive crystallization parameters; and (4) processes underlying the geochemical variation of the pluton. We highlight that phase equilibrium constraints are crucial for deriving reliable estimates for crystallization temperatures, melt H 2 O content, and fO 2 for ferroan A-type granites, and thus for unraveling Mesozoic crust formation and evolution in South China.

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Section: Discussionmentioning

confidence: 99%

Experimental Constraints on Intensive Crystallization Parameters and Fractionation in A‐Type Granites: A Case Study on the Qitianling Pluton, South China

et al. 2019

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“…(1) Processes related to the evolution of the melt Experimental and fluid/melt inclusion studies have demonstrated that during the last stage of magmatic crystallization, an exsolution process can occur, resulting in up to three products, namely, a silicate melt, vapour and a hydrosaline phase, the latter being described either as a fluid (Roedder, 1992;Kamenetsky et al, 2004;Alfonso and Melgarejo, 2008;Tartese and Boulvais, 2010;Chicharro et al, 2015;Webster et al, 2015;Assadzadeh et al, 2017) or as a melt (Badanina et al, 2004;Veksler, 2004;Thomas and Davidson, 2013;Huang et al, 2015).…”

Section: S214mentioning

confidence: 99%

Textural and mineral-chemistry constraints on columbite-group minerals in the Penouta deposit: evidence from magmatic and fluid-related processes

et al. 2018

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The Penouta Sn-Ta deposit, in the northwest of Spain, is a greisenized granitic cupola where Ta minerals occur mainly as disseminations in a leucogranite body intruded in Precambrian–Lower Cambrian gneisses and mica-schists. This leucogranite is a medium- to fine-grained inequigranular rock consisting mainly of quartz, albite, K-feldspar and muscovite. Accessory minerals are mainly of spessartine, zircon, cassiterite, Nb-Ta oxides, monazite, xenotime, native bismuth and pyrite. The alteration processes were mainly albitization, muscovitization and kaolinitization.This leucogranite is peraluminous and P-poor, with 0.03–0.07 wt.% P2O5, 900–1500 ppm Rb, 30–65 ppm Cs, 120–533 ppm Li, 80–140 ppm Ta, 51–81 ppm Nb and up to 569 ppm of Sn.Mineralogical characterization of Nb-Ta oxide minerals was determined by X-ray diffraction, scanning electron microscopy, electron microprobe analysis and mineral liberation analysis. Mn-rich members of the columbite-group minerals (CGM) are the most common Ta-bearing phases, but microlite, wodginite, tapiolite and Ta-rich cassiterite occur also. CGM crystals are commonly zoned concentrically, with a Nb-rich core surrounded by a Ta-rich rim, with a sharp boundary between them. Convoluted zoning occurs also. Dissolution textures resulting from the corrosion of columbite and tantalite rims, in particular, are common. The Mn/(Mn + Fe) ratio varies between 0.33 and 0.97 and the Ta/(Ta + Nb) ratio between 0.07 and 0.93. Wodginite and microlite formed as late replacements of CGM and occur associated with tantalite and cassiterite. Subhedral to anhedral cassiterite crystals, usually up to 200 μm across, occur in two generations: the earlier one is Nb,Ta-poor whereas in the later generation, the Ta content can reach >9 wt.% of Ta2O5 and 1.7 wt.% of Nb. The presence of a fluid phase in the apical zone of the granite, probably related to the separation of a fluid/vapour of the melt, could explain the sponge-like textures, the Ta enrichment associated with these textures, the occurrence of Ta-enriched mineral phases (microlite and wodginite) and their common interstitial character.

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“…The Nb-Ta oxides are hosted by the silicate matrix, and display a simple core-rim normal progressive zoning and less frequently an oscillatory zoning (Figure 7). The presence of these oxides as inclusions within most primary minerals, such as muscovite and albite; as well as the inclusion of some albite within the coltan ( Figure 6), and chemical zoning of these oxides (Figure 7) allow for interpreting these crystals as magmatic in origin, as described in worldwide studies [4,6,9,10,12,28,36,37,105,[125][126][127][128]. CGM-I is characterized by high Mn# (0.52-0.89) and low Ta# (0.04-0.19) typical of earlier magmatic-stage products, and the observed differences in Mn# or Ta# values of the primary columbite minerals in the different facies strongly suggest a high differentiated magmatic environment during crystallization of the Mayo Salah leucogranite magma (Figure 8; [12]).…”

Section: The Mayo Salah Pluton: a Peraluminous Low-phosphorous Rare-mmentioning

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

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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...

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Differentiated rare-element mineralization in an ongonite–topazite composite dike at the Xianghualing tin district, Southern China: An electron-microprobe study on the evolution from niobium–tantalum-oxides to cassiterite

Cited by 38 publications

References 45 publications

Experimental Constraints on Intensive Crystallization Parameters and Fractionation in A‐Type Granites: A Case Study on the Qitianling Pluton, South China

Experimental Constraints on Intensive Crystallization Parameters and Fractionation in A‐Type Granites: A Case Study on the Qitianling Pluton, South China

Textural and mineral-chemistry constraints on columbite-group minerals in the Penouta deposit: evidence from magmatic and fluid-related processes

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

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