scholarly journals Major- and trace-element compositional variation of phlogopite from kimberlites and carbonatites as a petrogenetic indicator

2019 ◽  
Keyword(s):  
Trace Element ◽  
Compositional Variation ◽  
Petrogenetic Indicator

Major- and trace-element compositional variation of phlogopite from kimberlites and carbonatites as a petrogenetic indicator

Lithos ◽  
2009 ◽  
Vol 112 ◽  
pp. 372-384 ◽  
Author(s):  
E.P. Reguir ◽  
A.R. Chakhmouradian ◽  
N.M. Halden ◽  
V.G. Malkovets ◽  
P. Yang
Keyword(s):  
Trace Element ◽  
Compositional Variation ◽  
Petrogenetic Indicator

Dating polymetamorphism using titanite: Linking trace elements, textures, and ages

2021 ◽  
Author(s):  
Jesse Walters ◽  
Alicia Cruz-Uribe ◽  
Won Joon Song ◽  
Joshua Stone ◽  
Hanna Brooks ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Bulk Composition ◽  
Granulite Facies ◽  
Compositional Variation ◽  
Excimer Laser Ablation ◽  
Eu Anomaly ◽  
Fluid Infiltration ◽  
Icp Ms ◽  
The University

<p>Here we present titanite U-Pb dates from two banded calc silicate gneisses (SSP18-1A and 1B) from western Maine. Mineral textures and compositions display multiple phases of metamorphism. The peak lower granulite facies assemblage is Di + Kfs + Pl + Ttn, with little to no calcite present. Late Czo + Tr replaces Di + Pl, suggesting an influx of X<sub>H2O</sub> > 0.90 fluids. Nearby metapelites show the transition from sillimanite-bearing to muscovite-bearing assemblages, indicating that fluid infiltration may be widespread. Compositional maps of clinopyroxene in SSP18-1B show fracturing and rehealing of early Fe-rich diopside with late Mg-rich diopside. Both samples exhibit overprinting of An-rich plagioclase by increasingly Ab-rich plagioclase. Titanite grains in both samples exhibit BSE textures and compositional variation consistent with multiple phases of growth and dissolution-reprecipitation reactions.</p><p>Titanite trace element and U-Pb data were collected by LA-ICP-MS at the University of Maine using an ESI NWR193<sup>UC</sup> excimer laser ablation system coupled to an Agilent 8900 ICP-MS. Single spot ages range from 280 to 400 Ma with 12-20 Ma propagated 2SE. Four composition-date domains are identified in SSP18-1B: A. 400 ± 8 Ma (dark BSE cores), B. 372 ± 4 Ma (bright BSE cores), C. 342 ± 6 Ma (bright BSE cores, no Eu anomaly), and D. 302 ± 3 Ma (dark BSE rims, low LREE). Titanite Fe and Y concentrations increase with decreasing date, whereas Sr concentrations decrease. In clinopyroxene, Fe and Y decrease between high Fe-diopside and late Mg-diopside, placing the fracturing and rehealing events between 400 and 372 Ma. Strontium concentrations in titanite decrease between subsequent generations of plagioclase, diopside, and titanite, suggesting a continual fractionation of Sr from the reactive bulk composition. Low LREE in ca. 300 Ma titanite domains in both samples are consistent with the formation of texturally late allanite and clinozoisite, thus constraining the timing of the high X<sub>H2O</sub> fluid infiltration event. Zr-in-titanite temperatures for rims in the quartz-bearing SSP18-1B give a weighted mean T of 764 °C at 4.5 GPa, consistent with the muscovite-absent sillimanite-bearing assemblage in garnet cores from metapelite samples. However, the 100-150 °C lower Grt-Bt temperatures for metapelites are not consistent with peak metamorphic phase equilibria. Our data demonstrate the utility of linking titanite textures and trace element concentrations with those of other minerals to reveal past metamorphic and deformational events. Additionally, we show that titanite may reliably preserve U and Pb isotopic ratios, trace elements, and textures over subsequent high-T metamorphic events.</p>

Incorporation of REE into leucophanite: a compositional and structural study

2007 ◽  
Vol 71 (06) ◽  
pp. 625-640 ◽  
Author(s):  
H. Friis ◽  
T. Balić-Žunić ◽  
C. T. Williams ◽  
R. Garcia-Sanchez
Keyword(s):  
Trace Element ◽  
Element Concentration ◽  
Trace Element Concentration ◽  
Compositional Variation ◽  
Chemical Compositions ◽  
Charge Balance ◽  
Element Abundances ◽  
Chemical Factors ◽  
Crystallization Conditions ◽  
Compositional Zonation

Abstract The crystal structures of nine, and the chemical compositions of ten, natural samples of leucophanite, ideally NaCaBeSi2O6F, were investigated. The analysed samples display a large compositional variation with trace-element abundances >50,000 ppm, primarily due to rare earth elements (REE). Fromthese data, we propose a substitution scheme for the incorporation of REE for Ca, with additional Na substituting for Ca and the generation of vacancies to ensure charge balance. Compositional zonation was observed in some samples; this zonation correlates with variations in cathodoluminescence. The crystal structure of the nine analysed samples could all be refined in space group P212121. We found no evidence for a reduction of symmetry with increased trace-element concentration. Various twin combinations were observed and these seem related to crystallization conditions rather than structural or chemical factors.

Complementary Textural, Trace Element, and Isotopic Analyses of Sulfides Constrain Ore-Forming Processes for the Slate-Hosted Yuhengtang Au Deposit, South China

2021 ◽  
Vol 116 (8) ◽  
pp. 1825-1848
Author(s):  
Wei Li ◽  
Nigel J. Cook ◽  
Gui-Qing Xie ◽  
Jing-Wen Mao ◽  
Cristiana L. Ciobanu ◽  
...  
Keyword(s):  
Trace Element ◽  
South China ◽  
Sulfur Isotope ◽  
Gold Mineralization ◽  
Oscillatory Zoning ◽  
Compositional Variation ◽  
Rock Interaction ◽  
Icp Ms ◽  
Isotopic Analyses ◽  
Stage 1

Abstract Yuhengtang is a representative slate-hosted Au deposit in the Jiangnan orogenic belt, South China, with a reserve of ~55 t Au and an average grade of ~3.9 g/t. Gold mineralization is characterized by veinlet and disseminated ores comprising native gold, auriferous pyrite, and arsenopyrite. Paragenesis of the Yuhengtang deposit can be divided into three stages. Pre-ore stage 1 is composed of bedding-parallel layers of pyrite in slate of the Neoproterozoic Banxi Group. Main ore stage 2 represents the Au mineralization stage, and two distinct types of mineralization can be distinguished: visible Au-arsenopyrite-pyrite in quartz veinlets and auriferous arsenopyrite-pyrite disseminated within altered slate. Post-ore stage 3 consists of quartz-pyrite-calcite-ankerite veins. In this study, we integrate electron microprobe, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and high-resolution ion microprobe (SHRIMP) analyses to document textural, isotopic, and compositional variation among texturally complex pyrite and arsenopyrite assemblages in veinlet and disseminated ores. Additionally, LA-ICP-MS sulfur isotope mapping of pyrite highlights the covariation behavior between trace elements and sulfur isotopes at the grain scale, thus allowing the factors controlling sulfur isotope fractionation in hydrothermal Au deposits to be constrained. Pyrite, of sedimentary origin (stage 1), hosts negligible Au (<1.6 ppm) but is enriched in δ34S (15.6–25.8‰). Pyrite and arsenopyrite from stage 2 veinlet mineralization both display porous and dissolution-reprecipitation textures, have low Au concentrations (<4 and <78 ppm, respectively), and show a large variation in δ34S (–2.7 to 14.7‰ and –10.3 to 12.1‰, respectively). Pyrite and arsenopyrite from disseminated mineralization are, in contrast, characterized by oscillatory zoning textures and homogeneous appearance in backscattered electron (BSE) images, respectively, and are obvious by their relatively high contents of invisible Au (up to 90 and 263 ppm, respectively) and restricted range of δ34S values (0–5.3‰). These data suggest that magmatic-hydrothermal fluids contribute most of the Au and S budget in the Yuhengtang Au deposit. The major differences between veinlet and disseminated mineralization in terms of texture, trace element concentrations, and δ34S signatures of pyrite and arsenopyrite reflect contrasting mechanisms of Au precipitation and an evolution of physicochemical parameters of the ore-forming processes, particularly fO2 and the intensity of fluid-rock interaction. Pyrite from stage 3 appears homogeneous in BSE images yet displays a wide variation in δ34S values (1.2–31.4‰), further highlighting the controlling role played by physicochemical condition (i.e., pressure) on the δ34S signature of sulfides. Results of the coupled LA-ICP-MS sulfur and trace element mapping reveal that some zoned pyrite grains from stage 2 formed via overgrowth of Au-rich, light δ34S (2.4‰) hydrothermal rims onto Au-poor, heavy δ34S (18.1–18.5‰) sedimentary cores. All results support that multiple depositional mechanisms within a dynamic mineral system were responsible for Au concentration and define the specific textural, compositional, and sulfur isotope signatures of sulfides in coexisting vein/veinlet and disseminated mineralization. The new data highlight the ore-forming processes-based interpretation for ore genesis and underpin the importance of performing complementary in situ mineralogical analyses to elucidate the source and evolution of ore-forming fluids and enable correct interpretation of the architecture of the hydrothermal Au system.

scholarly journals Compositional Variation of Amphiboles During Magma Mixing: A Case Study of Huangyangshan A-Type Granite in Kalamaili Metallogenic Belt, East Junggar, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Chenyang Ye ◽  
Yonggang Feng ◽  
Ruxiong Lei ◽  
Gaoxue Yang
Keyword(s):  
Trace Element ◽  
Magma Mixing ◽  
Compositional Variation ◽  
Chemical Compositions ◽  
Magma Evolution ◽  
Metallogenic Belt ◽  
Trace Element Contents ◽  
Type Granite ◽  
Textural Evidence

The Huangyangshan A-type granitic pluton, distributed along the thrust fault in the Kalamaili region of East Junggar, Xinjiang, China, consists of alkaline granite containing abundant dioritic enclaves that formed via magma mixing. Both the host granite and the enclaves contain sodic amphiboles. The textural evidence indicates that amphiboles crystallized as a magmatic phase in both units. We determined major and trace element contents of amphiboles from both units to investigate the compositional variation of the amphiboles during the magma mixing process. The results show that cations of W- and C-site are influenced by chemical compositions of the magma whereas cations of A-, B- and T-site and Al3+ are controlled by crystal structure. Therefore, the variations of W- and C-site cations can reflect magma evolution. The core and rim of the amphiboles show similar trace element patterns, which also suggests that the amphiboles are late-stage phases. Furthermore, the amphibole-only thermometers yield reasonable estimates that are consistent with petrographic evidence. However, thermometers based on partition coefficients and all the currently available amphibole-based barometers that rely on Al contents or DAl cannot be applied to Fe-rich and Al-poor amphiboles.

scholarly journals Natural compositional variation of the river Meuse (Maas) suspended load: a 13 ka bulk geochemical record from the upper Kreftenheye and Betuwe Formations in northern Limburg

2000 ◽  
Vol 79 (4) ◽  
pp. 391-409 ◽  
Author(s):  
L.A. Tebbens ◽  
A. Veldkamp ◽  
S.B. Kroonenberg
Keyword(s):  
Trace Element ◽  
Industrial Revolution ◽  
Source Area ◽  
Time Frame ◽  
Suspended Load ◽  
Coarse Sand ◽  
Heavy Minerals ◽  
Compositional Variation ◽  
Fine Grained ◽  
Geological Unit

AbstractUnambiguously pristine and largely unpolluted sediments from the Late Weichselian and Holocene infillings of the Meuse residual channels in northern Limburg (the Netherlands) have been sampled to determine the natural compositional variation of the river’s suspended load.Bulk geochemical and granulometric analyses demonstrate that about 70% of the variation can be ascribed to hydrodynamic mineral sorting. Clay- and fine silt-sized phyllosilicates are the most important deterministic features, hosting the bulk of AI2O3, TiO2, K2O, MgO and trace element variability (notably Ba, Cr, Ga, Rb and V). Quartz is abundant in the fine and coarse sand fractions. Na2O and the Zr-Nb-Nd-Y quartet relate to albitic feldspars and heavy minerals, respectively, in the coarse silt fraction. The granulometry should therefore be quantified if geochemical baseline data for a particular geological unit or region are drawn up and for the evaluation of potentially polluted sediments.Although provenance has not changed, the composition of Meuse sediments cannot be considered constant over a time frame of 1000–10,000 years, due to climatic change. Weathering of phyllosilicates in both interstadial and interglacial soil environments and changing relative source-area contributions alter the detrital clay-mineral supply to raise the AI2O3 and lower the K2O and MgO contents in Holocene Meuse sediments. Early diagenetic siderite and vivianite formation in gyttjas causes relative accumulations of Fe2O3, MnO, P2O5, Co, Ni and notably Zn above the phyllosilicate background values. These accumulations are natural and show that sediments with elevated trace metal contents are not necessarily polluted. Very early atmospheric pollution in relation to ore mining and smelting activities in the Roman era, however, probably caused elevated Pb contents in Subatlantic humic clays and peat samples, long before the historic pollution of the Industrial Revolution started.The A12O3, Fe2O3 and CaO contents are used to predict the trace-element values as a function of sample granulometry, siderite/vivianite and lime content, respectively. As such, they can provide a sound basis for environmental researchers to determine baseline values of heavy metals in bulk samples of fine-grained fluvial sediments.

Trace elements in sulfides from the Maozu Pb-Zn deposit, Yunnan Province, China: Implications for trace-element incorporation mechanisms and ore genesis

2020 ◽  
Vol 105 (11) ◽  
pp. 1734-1751
Author(s):  
Zhenli Li ◽  
Lin Ye ◽  
Yusi Hu ◽  
Chen Wei ◽  
Zhilong Huang ◽  
...  
Keyword(s):  
Trace Element ◽  
Solid Solutions ◽  
Lower Layer ◽  
Compositional Variation ◽  
Strong Positive Correlation ◽  
Long Distance ◽  
Metallogenic Province ◽  
Mvt Deposit ◽  
Ore Bodies ◽  
Coupled Substitution

Abstract The Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province (SYGMP) is an important region for Pb-Zn resources in China. However, considerable controversy remains as to whether the Pb-Zn deposits are Mississippi Valley Type (MVT). The Maozu deposit, a typical example of the carbonate-hosted Pb-Zn deposits in the SYGMP, occurs in the late Ediacaran Dengying Formation and its ore bodies are divided into three types: lower layer (LL), vein layer (VL), and upper layer (UL) ore bodies based on their spatial relationship. In this study, laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was used to systematically analyze the trace-element compositions of sphalerite and galena in these three ore bodies. The results show that sphalerite is characterized by Cd and Ge enrichment; Fe, Mn, and Co depletion; and local In and Sn enrichment. Most of these elements likely appear as solid solutions in sphalerite and show a wide compositional variation, which is probably related to the medium- and low-temperature mixing of the ore-forming fluids. The local enrichment of In and Sn is likely attributed to the long-distance migration of ore-forming fluids through In-Sn-bearing volcaniclastic rocks. In vs. Sn and (Cu + Sb) vs. (Ag + Ge) show strong correlations and similar element distribution in the mapped images, indicating that these elements may be incorporated into sphalerite via a coupled substitution for Zn as 2In3+ + Sn4+ + 2☐ ↔ 5Zn2+ (☐ = vacancies) and 4(Cu+ + Sb3+) + (Ge4+ + 2Ag+) + 2☐ ↔ 13Zn2+. Galena is enriched in Ag and Sb with minor Cd and Se and depleted in Bi, and most of the elements may occur as solid solutions. Ag vs. Sb in galena displays a strong positive correlation, implying the coupled substitution of Ag+ + Sb3+ ↔ 2Pb2+. Notably, the majority of the trace-element concentrations gradually decrease in the order LL → UL except Fe, Co, Cu, and Ge, while Fe, In, and Sn in sphalerite and Ag and Sb in galena have the highest concentration in the VL, indicating that the VL is a secondary migration channel for the ore-forming fluids. Furthermore, the trace-element compositions of the sulfides in the Maozu Pb-Zn deposit are consistent with the typical MVT deposit (hosted in the carbonate sequence) but are markedly different from sedimentary exhalative (SEDEX), volcanogenic massive sulfide (VMS) and skarn-type deposits. Based on these results, as well as the geological and geochemical characteristics of the deposit, the Maozu Pb-Zn deposit is an MVT deposit.

Compositional variation in accessory phases: A multi-faceted petrogenetic indicator

Lithos ◽  
2006 ◽  
Vol 88 (1-4) ◽  
pp. vii-ix
Author(s):  
Joseph M. Pyle ◽  
Julia A. Baldwin
Keyword(s):  
Compositional Variation ◽  
Petrogenetic Indicator

Compositional variation of the tennantite–tetrahedrite solid-solution series in the Schwarzwald ore district (SW Germany): The role of mineralization processes and fluid source

2010 ◽  
Vol 74 (2) ◽  
pp. 309-339 ◽  
Author(s):  
S. Staude ◽  
T. Mordhorst ◽  
R. Neumann ◽  
W. Prebeck ◽  
G. Markl
Keyword(s):  
Solid Solution ◽  
Trace Element ◽  
Host Rock ◽  
Trace Element Content ◽  
Element Content ◽  
Compositional Variation ◽  
Solid Solution Series ◽  
Solution Series ◽  
Red Bed ◽  
Ore District

AbstractThe study presents analysis from members of the tennantite–tetrahedrite solid-solution series (‘fahlore’) from 78 locations in the Schwarzwald ore district of SW Germany. Electron microprobe analysis is used to correlate the compositional variations of the fahlores with mineral association, host rock, tectonic history and precipitation mechanisms. Results indicate that most fahlores from gneiss-hosted veins do not have distinctive geochemical characteristics and range from tetrahedrite to tennantite end-member composition with variable trace-element content. However, diagenetically formed fahlore has a near-end-member tennantite composition with very small trace-element content. Red-bed-hosted fahlore formed by fluid mixing is tennantite enriched in Hg that probably has its source in the red-bed sediments. Fahlore formed from granite-related late-magmatic fluids, or from mixing of fluids of which one has equilibrated with granitic basement rocks, is typically As- and Bi-rich (up to 22.2 wt.% Bi). Gneiss-hosted fahlore formed by fluid cooling is Ag-rich near-end-member tetrahedrite. Some fahlores reflect their paragenetic association, e.g. a large Ag content in association with Ag-bearing minerals or a large Co and Ni in association with Co- and Ni-arsenides.Although they have similar compositions, gneiss-hosted fahlores show systematic variations in Ag contents and Fe/Zn ratios between the Central and the Southern Schwarzwald with Fe-rich fahlore in higher stratigraphic levels (North) and Zn- and Ag-rich fahlore in lower stratigraphic levels (South). We show that fahlore composition varies with precipitation mechanism (cooling vs. mixing vs. diagenesis), depth of formation, paragenetic association and host rock. Comparison with fahlores from other European occurrences indicates that these conclusions are consistent with fahlore systematics found elsewhere, and could be used to infer details of ore-forming processes.

Tourmaline growth and evolution in S-type granites and pegmatites: constraints from textural, chemical and B-isotopic study from the Gangpur Schist Belt granitoids, eastern India

2021 ◽  
pp. 1-14
Author(s):  
Tuhin Chakraborty
Keyword(s):  
Trace Element ◽  
Isotope Composition ◽  
Isotopic Signature ◽  
Compositional Variation ◽  
Schist Belt ◽  
Eastern India ◽  
Isotopic Study ◽  
Tectonic Zone ◽  
Type Granite ◽  
Central Indian Tectonic Zone

Abstract An extensive dataset of major- and trace-element and B-isotope composition related to the compositional variation of the tourmalines from the S-type granite and pegmatite from the Upper Bonai and Gangpur Group granitoids, eastern India, is provided. The Gangpur Schist Belt, consisting of the Upper Bonai and Gangpur Group, lies at the eastern end of the Proterozoic Central Indian Tectonic Zone. An attempt to constrain the source of the boron isotope and describe the magmatic–hydrothermal evolution of the granite–pegmatite system is made. The tourmalines record generally low trace-element concentrations, with the exception of some elements such as Zn, Li, Ga, Mn and Ti. The Zn and Li concentration increases from the tourmalines in the granites to the tourmalines in the pegmatite. Trace-element compositions also vary slightly from the core tourmaline to the rim tourmaline. Tourmalines in granites/pegmatites are mostly Fe-rich schorl, and have S-type B-isotopic signature (δ11B = −10‰ to −12‰). Their chemistries reflect changing salinities of the granitic melts as well as vapour exsolution during progressive crystallization. This study indicates that the tourmalines in the pegmatites crystallized from evolved flux-element-rich (F, B, Li) melt, probably after the crystallization of granite-forming melt.

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