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.

Feldspar crystallization under magma-mixing conditions shown by cathodoluminescence and geochemical modelling – a case study from the Karkonosze pluton (SW Poland)

2004 ◽  
Vol 68 (4) ◽  
pp. 561-577 ◽  
Author(s):  
E. Słaby ◽  
J. Götze
Keyword(s):  
Magma Mixing ◽  
Main Tool ◽  
Precise Determination ◽  
Geochemical Modelling ◽  
Magma Evolution ◽  
Sw Poland ◽  
Crystallization Path ◽  
Geochemical Mass Balance

AbstractFeldspars from the Karkonosze pluton (SW Poland) display many features compatible with magma mixing. The mixing hypothesis has been tested using a geochemical mass balance law resulting in two possible paths of magma hybridization. Based on the results of the geochemical calculation, feldspar samples have been chosen along both mixing lines for cathodoluminescence (CL) investigation which was used as the main tool for the reconstruction of their crystallization path. Changes in the conditions of nucleation and crystallization of the feldspars as well as their movement within the magma chamber have been recognized due to different luminescence characteristics. These changes in the conditions of crystallization obtained by CL allow a precise determination of the genetic affinity of the samples to more mafic or more felsic environments.The results of the present study proved CL to be a valuable tool for the study of crystal-growth morphologies in a dynamic, turbulent environment and also as a geochemical tool for the reconstruction of various petrogenetic mechanisms (e.g. magma hybridization). Accordingly, the combination of CL with geochemical modelling provides corresponding information about magma evolution in an open system.

Techniques and methodology used in a mineralogical and osmium isotope study of platinum group minerals from alluvial deposits in Colombia, California, Oregon and Alaska

1997 ◽  
Vol 61 (406) ◽  
pp. 367-375 ◽  
Author(s):  
I. C. Lyon ◽  
H. Tamana ◽  
D. J. Vaughan ◽  
A. J. Criddle ◽  
J. M. Saxton ◽  
...  
Keyword(s):  
Trace Element ◽  
Alluvial Deposits ◽  
Ion Probe ◽  
Platinum Group Minerals ◽  
Placer Deposits ◽  
Trace Element Contents ◽  
Isotope Study ◽  
Platinum Group ◽  
Textural Evidence ◽  
Rhenium Content

AbstractPlatinum-group minerals (PGM) from placer deposits in Colombia, California, Oregon and Alaska were investigated with the electron microprobe, proton microprobe (μ-PIXE) and ion probe to analyse their major and trace element contents and 187Os/186Os isotopic ratios. Most of the grains in the samples investigated proved to be essentially homogeneous alloys of Pt-Fe and Os-Ir-Ru although a few of them contained inclusions of other PGM such as cooperite and laurite. Detailed analyses were undertaken on the Os-Ir-Ru alloy phases.The 187Os/186Os isotope ratios fell into a range from 1.005 to 1.156 and are consistent with data published on PGM from other placer deposits from these regions. The ratios, together with the trace element data (and in particular the low rhenium content) determined by ion probe and μ-PIXE, indicate that crustal osmium was not incorporated in the grains and that no significant evolution of the 187Os/186Os ratios occurred during their history. These data, along with mineralogical and textural evidence, are consistent with a mantle origin for the grains through ultramafic intrusions, although the data do not entirely rule out alternative interpretations.

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.

scholarly journals Uranium Mineralogical and Chemical Features of the Na-Metasomatic Type Uranium Deposit in the Longshoushan Metallogenic Belt, Northwestern China

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 335 ◽  
Author(s):  
Chi-Da Yu ◽  
Kai-Xing Wang ◽  
Xiao-Dong Liu ◽  
Michel Cuney ◽  
Jia-Yong Pan ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Hydrothermal Fluid ◽  
Uranium Deposit ◽  
Northwestern China ◽  
Compositional Variation ◽  
Chemical Compositions ◽  
Metallogenic Belt ◽  
Uranium Minerals ◽  
Chemical Dating

The Longshoushan Metallogenic Belt (northwestern China) is known for its word-class Jinchuan Ni-Cu sulfide (Pt) deposit and is also an important uranium metallogenic belt. The Jiling uranium deposit in this belt is a typical Na-metasomatic uranium deposit, which rarely occurs in China. Mineralization in the Jiling uranium deposit is hosted in granitoids that have suffered a Na-metasomatic alteration. There are three kinds of uranium minerals, including uraninite, pitchblende, and coffinite in the Jiling uranium deposit. Pitchblende is the predominant uranium mineral. Integrating the mineralogy and geochemistry of uranium minerals, and in situ electron microprobe analyzer (EMPA) U-Th-Pb chemical dating, we aimed to unravel the age and nature of the mineralization, to decipher the characteristics of the hydrothermal alteration and the U mineralization process. Based on the microtextural features and compositional variations, primary uraninite was altered to uraninite A and B, and fresh pitchblende was altered to pitchblende A and B. The best-preserved uraninite crystals displayed a euhedral-shape with high Pb and low SiO2, CaO, FeO, and Al2O3 contents, and was interpreted as primary uraninite. The EMPA U-Th-Pb chemical ages revealed that uraninite may have formed at 435.9 ± 3.3 Ma. High ThO2 + ΣREE2O3 + Y2O3 contents illustrated that the best preserved uraninite crystallized at a high temperature. Altered pitchblende A showed a relatively brighter gray color in backscattered electron (BSE) images and with a lower SiO2 content than B. Three analysis spots of the fresh pitchblende showed low contents of ΣSiO2 + CaO, indicating no obvious alteration. EMPA U-Th-Pb chemical dating gave a mean chemical age of 361 Ma. The low Th + ΣREE2O3 contents indicated that this pitchblende formed at a relatively low temperature. According to the different characteristics of occurrence and chemical composition, the coffinite in the Jiling uranium deposit can be divided into coffinite A and B, respectively. The compositional variation of the fresh and altered uraninite and pitchblende indicated that both uraninite and pitchblende underwent at least two discrete hydrothermal fluid alterations. The U mineralization was divided into two stages; uraninite was formed at a high temperature and possibly from a magmatic-hydrothermal fluid during ore stage I. Then, pitchblende was formed at a low temperature, during ore stage II. According to the petrographic observations and their chemical compositions, coffinite A and B resulted from the alterations of uraninite and pitchblende, respectively.

Geochemistry and mineralogy as indicators of parental affinity for Cenozoic bentonites: a case study from S. Croce di Magliano (southern Apennines, Italy)

Clay Minerals ◽  
1996 ◽  
Vol 31 (3) ◽  
pp. 391-401 ◽  
Author(s):  
R. Laviano ◽  
G. Mongelli
Keyword(s):  
Trace Element ◽  
Mineralogical Composition ◽  
Southern Apennines ◽  
Elemental Ratios ◽  
Size Fractions ◽  
Diagenetic Alteration ◽  
Volcanic Events ◽  
Trace Element Contents ◽  
The Eu

AbstractThe major and trace element contents and mineralogical composition of Cenozoic bentonites from the southern Apennines (Italy) have been determined, for the whole-rocks and the <2 µm size-fractions, in order to constrain parental affinities. The main mineralogical and chemical differences have been recognized in eleven samples allowing them to be grouped into two distinct subsets. The differences are based on smectite abundance, occurrence or lack of detrital clay phases, different contents of Ti, Fe, Mn, K, P, Rb, Sc, V, Cr and Ni and differences in the Eu/Eu* and Ti/Al elemental ratios. These ratios indicate an affinity for felsic volcanics for the subset showing high smectite contents. The low smectite subset shows, instead, an affinity for Cretaceous-Oligocene southern Apennine shales. A similar result is obtained using the La-Th-Sc and Th-Sc-Zr/10 diagrams. We suggest that during the deposition of the southern Apennine shales, episodic volcanic events took place. These were associated with the suture stage of the Tethyan ocean that promoted accumulation of felsic ash in the related basin and the diagenetic alteration of these materials produced bentonitic layers interbedded with shales.

The geochemistry of carbonate cements in the Avalon Sand, Grand Banks of Newfoundland

1985 ◽  
Vol 49 (352) ◽  
pp. 457-467 ◽  
Author(s):  
Ian Hutcheon ◽  
Cynthia Nahnybida ◽  
H. R. Krouse
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Meteoric Water ◽  
Trace Element Data ◽  
Isotopic Data ◽  
Grand Banks ◽  
Carbonate Cements ◽  
Trace Element Contents ◽  
Oxygen Isotopic ◽  
Textural Evidence

AbstractCalcite cements from the Lower Cretaceous Avalon zone of the Hibernia field are, in places, extensively recrystallized, which complicates interpretation of the chemical and isotopic data. The oxygen isotopic data are widely scattered with δ18O ranging between +1.6 and −9.2 for calcite and siderite. Siderite has lower δ13C values (−6.6 to −13.2) than calcite +12.4 to −9.8. Typical trace element contents determined by ICP on acid-leached samples, range from 270 to 2100 ppm Sr and 180 to 2200 ppm Zn in calcite.The trace element data indicate that some of the calcite has been precipitated from, or recrystallized by meteoric water. The trace elements show trends related to variations in δ18O in such a way as to imply that not all the spread to low δ18O values can be attributed to meteoric water influence alone. The data are not well enough constrained to calculate meaningful temperatures, but the range of °18O values probably represents an elevated range of temperatures of precipitation or recrystallization.Microprobe analyses show that non-recrystallized fossils have a composition distinctly different from veins, cements, and recrystallized fossils, all of which are similar. The compositions of calcite cements are highly variable, with FeO (for example) ranging from 0.15 to 4.39 wt. %, but show no consistent patterns of zonation. Fossil fragments which show no textural evidence of recrystallization have low FeO contents (0.2 wt. %). Meteoric water, believed to be responsible for at least some of the cementation and recrystallization observed, probably entered the Avalon during and after formation of the mid-Cretaceous unconformity.

scholarly journals Evolution of Nb–Ta Oxide Minerals and Their Relationship to the Magmatic-Hydrothermal Processes of the Nb–Ta Mineralized Syenitic Dikes in the Panxi Region, SW China

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1204
Author(s):  
Yuan Xue ◽  
Ningyue Sun ◽  
Guowu Li
Keyword(s):  
Alkaline Rock ◽  
Hydrothermal Fluids ◽  
Chemical Compositions ◽  
Magma Evolution ◽  
Compositional Zoning ◽  
Metallogenic Belt ◽  
Pyrochlore Group ◽  
Texture Characteristics ◽  
Mineralization Processes ◽  
Oxide Minerals

Previous geochemical and petrological studies have concluded that initially magmatic Nb–Ta mineralization is often modified by post-magmatic hydrothermal fluids; however, there is still a lack of mineralogical evidence for the syenite-related Nb–Ta deposit. From the perspective of Nb–Ta minerals, the pyrochlore supergroup minerals have significance for indicating the fluid evolution of alkaline rock or related carbonatite type Nb–Ta deposits. The Panzhihua–Xichang (Panxi) region is a famous polymetallic metallogenic belt in southwestern China, abound with a huge amount of Nb–Ta mineralized syenitic dikes. This study focuses on the mineral textures and chemical compositions of the main Nb–Ta oxide minerals (including columbite-(Fe), fersmite, fergusonite-(Y), and especially pyrochlore group minerals) in samples from the Baicao and Xiaoheiqing deposits, in the Huili area, Panxi region, to reveal the magma evolution process of syenitic-dike-related Nb–Ta deposits. The Nb–Ta oxides in the Huili syenites are commonly characterized by a specific two-stage texture on the crystal scale, exhibiting a complex metasomatic structure and compositional zoning. Four types of pyrochlore group minerals (pyrochlores I, II, III, and IV) formed in different stages were identified. The euhedral columbite-(Fe), fersmite, and pyrochlores I and II minerals formed in the magmatic fractional crystallization stage. Anhedral pyrochlore III minerals are linked to the activity of magma-derived hydrothermal fluids at the late stages of magma evolution. The pyrochlore IV minerals and fergusonite-(Y) tend to be more concentrated in areas that have undergone strong albitization, which is a typical phenomenon of hydrothermal alteration. These mineralogical phenomena provide strong evidences that the magmatic-hydrothermal transitional stage is the favored model for explaining the Nb–Ta mineralization process. It is also concluded that the changes in chemical composition and texture characteristics for pyrochlore group minerals could serve as a proxy for syenite-related Nb–Ta mineralization processes.

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