Generation of Cretaceous high-silica granite by complementary crystal accumulation and silicic melt extraction in the coastal region of southeastern China

2021 ◽  
Author(s):  
Jing-Yuan Chen ◽  
Jin-Hui Yang ◽  
Ji-Heng Zhang ◽  
Jin-Feng Sun ◽  
Yu-Sheng Zhu ◽  
...  
Keyword(s):  
Coastal Region ◽  
Parental Magma ◽  
Mafic Magma ◽  
Alkali Feldspar ◽  
Southeastern China ◽  
Upward Migration ◽  
Porphyritic Granite ◽  
Melt Extraction ◽  
Isotopic Compositions ◽  
High Silica

It is generally hypothesized that high-silica (SiO2 > 75 wt%) granite (HSG) originates from crystal fractionation in the shallow crust. Yet, identifying the complementary cumulate residue of HSG within plutons remains difficult. In this work, we examine the genetic links between the porphyritic monzogranite and HSG (including porphyritic granite, monzogranite, and alkali feldspar granite) from the coastal area of southeastern China using detailed zircon U-Pb ages, trace elements, Hf-O isotopes, and whole-rock geochemistry and Nd-Hf isotopic compositions. Zircon U-Pb ages indicate that the porphyritic monzogranite and HSG are coeval (ca. 96−99 Ma). The HSG and porphyritic monzogranite have similar formation ages within analytic error, identical mineral assemblages, similar Nd-Hf isotopic compositions, and consistent variations in their zircon compositions (i.e., Eu/Eu*, Zr/Hf, and Sm/Yb), which suggests that their parental magma came from a common silicic magma reservoir and that the lithological differences are the result of melt extraction processes. The porphyritic monzogranite has relatively high SiO2 (70.0−73.4 wt%), Ba (718−1070 ppm), and Sr (493−657 ppm) contents, low K2O and Rb concentrations and low Rb/Sr ratios (0.1−0.2), and it displays weak Eu anomalies (Eu/Eu* = 0.57−0.90). Together with the petrographic features of the porphyritic monzogranite, these geochemical variations indicate that the porphyritic monzongranite is the residual silicic cumulate of the crystal mush column. The HSG (SiO2 = 75.0−78.4) has variable Rb/Sr ratios (2−490) and very low Sr (1−109 ppm) and Ba (9−323 ppm) contents. Zircon from the HSG and porphyritic monzogranite overlap in Eu/Eu*, Zr/Hf, and Sm/Yb ratios and Hf contents; however, some zircon from the HSG show very low Eu/Eu* (<0.1) and Zr/Hf ratios. These features suggest that the HSG represents the high-silica melt that was extracted from a crystal-rich mush. The injection of mantle-derived hotter mafic magma into the mush column and the exsolution of F/Cl−-enriched volatiles (or fluids) from the interstitial melt rejuvenated the pre-existing highly crystalline mush. Subsequent extraction and upward migration of silicic melt resulting from compaction of the mush column formed the HSG at shallow crustal levels, which left the complementary crystal residue solidified as porphyritic monzogranite at the bottom.

scholarly journals Supplemental Material: Generation of Cretaceous high-silica granite by complementary crystal accumulation and silicic melt extraction in the coastal region of southeastern China

2021 ◽  
Author(s):  
Jing-Yuan Chen ◽  
et al.
Keyword(s):  
Coastal Area ◽  
Coastal Region ◽  
Major And Trace Elements ◽  
Granitic Rocks ◽  
Isotopic Data ◽  
Southeastern China ◽  
Melt Extraction ◽  
High Silica ◽  
Crystal Accumulation ◽  
Se China

Table S1: Zircon Cameca 1280 U-Pb data for the granitic rocks from SE Fujian, coastal area of SE China; Table S2: LA-ICPMS zircon U-Pb data for the granitic rocks from SE Fujian, coastal area of SE China; Table S3: Major and trace elements of the granitic rocks from SE Fujian, coastal area of SE China; Table S4: Whole-rock Sm-Nd isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S5: Whole-rock Lu-Hf isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S6: Zircon Hf-O isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S7: Zircon trace element of the granitic rocks from SE Fujian, coastal area of SE China.

scholarly journals Supplemental Material: Generation of Cretaceous high-silica granite by complementary crystal accumulation and silicic melt extraction in the coastal region of southeastern China

2021 ◽  
Author(s):  
Jing-Yuan Chen ◽  
et al.
Keyword(s):  
Coastal Area ◽  
Coastal Region ◽  
Major And Trace Elements ◽  
Granitic Rocks ◽  
Isotopic Data ◽  
Southeastern China ◽  
Melt Extraction ◽  
High Silica ◽  
Crystal Accumulation ◽  
Se China

Table S1: Zircon Cameca 1280 U-Pb data for the granitic rocks from SE Fujian, coastal area of SE China; Table S2: LA-ICPMS zircon U-Pb data for the granitic rocks from SE Fujian, coastal area of SE China; Table S3: Major and trace elements of the granitic rocks from SE Fujian, coastal area of SE China; Table S4: Whole-rock Sm-Nd isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S5: Whole-rock Lu-Hf isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S6: Zircon Hf-O isotopic data of the granitic rocks from SE Fujian, coastal area of SE China; Table S7: Zircon trace element of the granitic rocks from SE Fujian, coastal area of SE China.

scholarly journals Transient rhyolite melt extraction to produce a shallow granitic pluton

2021 ◽  
Vol 7 (21) ◽  
pp. eabf0604
Author(s):  
Allen J. Schaen ◽  
Blair Schoene ◽  
Josef Dufek ◽  
Brad S. Singer ◽  
Michael P. Eddy ◽  
...  
Keyword(s):  
Time Scales ◽  
Explosive Eruptions ◽  
Upper Crust ◽  
Saturation Model ◽  
Granitic Pluton ◽  
Melt Extraction ◽  
High Silica ◽  
Melt Segregation ◽  
Zircon Saturation

Rhyolitic melt that fuels explosive eruptions often originates in the upper crust via extraction from crystal-rich sources, implying an evolutionary link between volcanism and residual plutonism. However, the time scales over which these systems evolve are mainly understood through erupted deposits, limiting confirmation of this connection. Exhumed plutons that preserve a record of high-silica melt segregation provide a critical subvolcanic perspective on rhyolite generation, permitting comparison between time scales of long-term assembly and transient melt extraction events. Here, U-Pb zircon petrochronology and 40Ar/39Ar thermochronology constrain silicic melt segregation and residual cumulate formation in a ~7 to 6 Ma, shallow (3 to 7 km depth) Andean pluton. Thermo-petrological simulations linked to a zircon saturation model map spatiotemporal melt flux distributions. Our findings suggest that ~50 km3 of rhyolitic melt was extracted in ~130 ka, transient pluton assembly that indicates the thermal viability of advanced magma differentiation in the upper crust.

A Study of Fenitization in Mafic Rocks, with Special Reference to the Callander Bay Complex

1972 ◽  
Vol 9 (10) ◽  
pp. 1254-1261 ◽  
Author(s):  
K. L. Currie ◽  
J. Ferguson
Keyword(s):  
Close Association ◽  
Parental Magma ◽  
Alkali Feldspar ◽  
High Water ◽  
High Water Content ◽  
Ionic Exchange ◽  
Exchange Reactions ◽  
Carbonatite Complex ◽  
Alkali Chloride ◽  
Mafic Rocks

Garnet amphibolite lenses around the Callander Bay alkaline carbonatite complex are transformed by fenitization into alkali feldspar – hastingsite rocks, partly by ionic exchange reactions, and partly by replacement of mafic minerals. The chemical composition of the mafic rocks converges with fenitization towards that of salic fenites. Literature data suggest that these observations are typical of mafic fenites. The fenitizing solutions at Callander Bay were alkali chloride brines 10–25 molar in strength with K/Na + K ratios of 0.23, and a K/H+ ratio of 30. These brines arose from the silicate portion of the complex, and the close association of carbonatite and fenite stems from a factor common to both carbonatite and alkaline silicate rocks, probably a high water content in the parental magma.

scholarly journals Supplemental Material: A model involving amphibolite lower crust melting and subsequent melt extraction for leucogranite generation

2021 ◽  
Author(s):  
Liqiang Wang ◽  
et. al
Keyword(s):  
Trace Element ◽  
Lower Crust ◽  
Partition Coefficients ◽  
Geochemical Modeling ◽  
Magma Source ◽  
Isotopic Data ◽  
Melt Extraction ◽  
Isotopic Compositions ◽  
Age Determinations

Table S1: Isotopic data of U-Pb age determinations on zircons of the Anglonggangri biotite-muscovite and garnet-muscovite granites; Table S2: 40Ar-39Ar dating results for muscovite from the pegmatite in the Anglonggangri area; Table S3: Whole-rock major and trace element compositions of the Anglonggangri biotite-muscovite and garnet-muscovite granites; Table S4: Whole-rock Pb isotopic compositions of the Anglonggangri biotite-muscovite and garnet-muscovite granites; Table S5: Zircon in situ Lu-Hf isotopic compositions of the Anglonggangri biotite-muscovite granite; Table S6: Partition coefficients and assumed magma source compositions used in geochemical modeling; Table S7: Partition coefficients and assumed compositions used in geochemical modeling and the calculated results.

scholarly journals Accessory minerals and evolution of tin-bearing S-type granites in the western segment of the Gemeric Unit (Western Carpathians)

2018 ◽  
Vol 69 (5) ◽  
pp. 483-497 ◽  
Author(s):  
Igor Broska ◽  
Michal Kubiš
Keyword(s):  
Mineral Assemblage ◽  
Alkali Feldspar ◽  
Rare Metal ◽  
Tectonic Activity ◽  
Accessory Mineral ◽  
Porphyritic Granite ◽  
Western Segment ◽  
Gemeric Unit ◽  
Highly Evolved

Abstract The S-type accessory mineral assemblage of zircon, monazite-(Ce), fluorapatite and tourmaline in the cupolas of Permian granites of the Gemeric Unit underwent compositional changes and increased variability and volume due to intensive volatile flux. The extended S-type accessory mineral assemblage in the apical parts of the granite resulted in the formation of rare-metal granites from in-situ differentiation and includes abundant tourmaline, zircon, fluorapatite, monazite-(Ce), Nb–Ta–W minerals (Nb–Ta rutile, ferrocolumbite, manganocolumbite, ixiolite, Nb–Ta ferberite, hübnerite), cassiterite, topaz, molybdenite, arsenopyrite and aluminophosphates. The rare-metal granites from cupolas in the western segment of the Gemeric Unit represent the topaz–zinnwaldite granites, albitites and greisens. Zircon in these evolved rare-metal Li–F granite cupolas shows a larger xenotime-(Y) component and heterogeneous morphology compared to zircons from deeper porphyritic biotite granites. The zircon Zr/Hfwt ratio in deeper rooted porphyritic granite varies from 29 to 45, where in the differentiated upper granites an increase in Hf content results in a Zr/Hfwt ratio of 5. The cheralite component in monazite from porphyritic granites usually does not exceed 12 mol. %, however, highly evolved upper rare-metal granites have monazites with 14 to 20 mol. % and sometimes > 40 mol. % of cheralite. In granite cupolas, pure secondary fluorapatite is generated by exsolution of P from P-rich alkali feldspar and high P and F contents may stabilize aluminophosphates. The biotite granites contain scattered schorlitic tourmaline, while textural late-magmatic tourmaline is more alkali deficient with lower Ca content. The differentiated granites contain also nodular and dendritic tourmaline aggregations. The product of crystallization of volatile-enriched granite cupolas are not only variable in their accessory mineral assemblage that captures high field strength elements, but also in numerous veins in country rocks that often contain cassiterite and tourmaline. Volatile flux is documented by the tetrad effect via patterns of chondrite normalized REEs (T1,3 value 1.46). In situ differentiation and tectonic activity caused multiple intrusive events of fluid-rich magmas rich in incompatible elements, resulting in the formation of rare-metal phases in granite roofs. The emplacement of volatile-enriched magmas into upper crustal conditions was followed by deeper rooted porphyritic magma portion undergoing second boiling and re-melting to form porphyritic granite or granite-porphyry during its ascent.

scholarly journals Architecture of a Super-sized Magma Chamber and Remobilization of its Basal Cumulate (Peach Spring Tuff, USA)

2020 ◽  
Vol 61 (1) ◽  
Author(s):  
Michelle L Foley ◽  
Calvin F Miller ◽  
Guilherme A R Gualda
Keyword(s):  
Trace Element ◽  
Chemical Interaction ◽  
Mafic Magma ◽  
Heating Event ◽  
Peach Spring Tuff ◽  
Crystal Fraction ◽  
High Silica ◽  
Compositional Gradients ◽  
Crystal Accumulation ◽  
Phase Chemistry

Abstract Using a combination of petrological and geochemical approaches, we investigate processes prior to and during eruption of the Miocene supereruption of the Peach Spring Tuff (PST; Arizona–California–Nevada), including those leading to assembly and destruction of its reservoir(s). We compare the dominant high-silica rhyolite outflow of the PST with the sparsely exposed but distinctive crystal-rich trachyte capping unit, which matches intracaldera trachyte in composition, texture, and phenocryst content. The details of the diverse glass chemistry in fiamme and pumice in the capping unit, coupled with glass compositions in the rhyolite outflow and phase chemistry in general, illuminate critical aspects of chamber geometry, conditions, and processes at the onset of the supereruption. Our results are consistent with a relatively simple single-chamber reservoir for the PST where the crystal-poor, high-silica rhyolite portion directly overlies a mushy, cumulate base. Rhyolite-MELTS phase-equilibria and amphibole geobarometers indicate that the high-silica rhyolite was extracted from its cumulate mush at a depth of ∼9·5–11 km (∼260–300 MPa) and subsequently stored and crystallized at ∼7·0–8·5 km (190–230 MPa). Three types of glass are distinguishable in PST pumice: trachyte (Trg; ∼68 wt% SiO2), low-silica rhyolite (LSRg; ∼72), and high-silica rhyolite (HSRg; ∼76·5). As many as three discrete, complexly mingled glasses are present in single trachyte fiamme. Trace element concentration profiles in sanidine and plagioclase phenocrysts from both the trachyte and HSR support growth from multiple distinct melts (Trg, LSRg, and HSRg). Glasses in trachyte fiamme have zircon saturation temperatures ≥100 °C higher than HSR glasses (850–920 vs ∼770 °C) and compositions indicating dissolution of cumulate phases: very high Zr and Zr/Hf (zircon), REE (chevkinite and titanite), Ba and Sr (feldspars), and P (apatite). Dominant processes of crystal accumulation in the formation of a mushy base, followed by efficient melt extraction, led to the formation of the voluminous high-silica rhyolite melt-rich body overlying a residual cumulate of trachytic composition. This was followed by heating, partial dissolution, and remobilization of the basal cumulate. This history is reflected in the contrasts that are evident in the PST (elemental compositions of pumice, phenocrysts, and glasses; crystal-fraction; temperatures). Reheating was presumably a result of injection of hot mafic magma, but isotopic uniformity of trachyte and rhyolite indicates minimal chemical interaction with this magma. Variability in dissolution textures in phenocrysts in the trachyte, revealed by resorbed and embayed shapes, and the large range of glass trace element concentrations, together with variable temperatures recorded in glasses by zircon and apatite saturation thermometry, suggest that heat transfer from the hotter rejuvenating magma was unevenly distributed. The late-stage heating event probably contributed to the onset of eruption, providing the thermal energy necessary to reduce the crystal fraction within the cumulate below the mechanical lock point. We estimate ∼50 % of the original cumulate phenocrysts dissolved before eruption, using Rhyolite-MELTS and trace element modeling. Sharp contacts with micron-scale compositional gradients between contrasting glass types in individual trachyte fiamme suggest that juxtaposition of contrasting magmas from different parts of the reservoir occurred during eruption.

Concentration Mechanisms of Rare Earth Element-Nb-Zr-Be Mineralization in the Baerzhe Deposit, Northeast China: Insights from Textural and Chemical Features of Amphibole and Rare Metal Minerals

2020 ◽  
Author(s):  
Mingqian Wu ◽  
Iain M. Samson ◽  
Kunfeng Qiu ◽  
Dehui Zhang
Keyword(s):  
Rare Earth ◽  
Northeast China ◽  
Stage Iv ◽  
Alkali Feldspar ◽  
Rare Metal ◽  
Stage Ii ◽  
Stage Iii ◽  
Partial Replacement ◽  
Porphyritic Granite ◽  
Rare Metal Mineralization

Abstract The Early Cretaceous Baerzhe deposit in Inner Mongolia, Northeast China, hosts a world-class resource of rare earth elements (REEs), niobium, zirconium, and beryllium. In contrast to previous interpretations of the deposit as a multiphase, miaskitic alkaline granite, our observations of the relationships of various rock phases, the textural features and chemical evolution of amphibole, and the distribution of primary and secondary mineral assemblages suggest that the igneous phases evolved from a hypersolvus porphyritic granite, through a variably altered transsolvus granite, both of which are miaskitic, to a strongly altered, agpaitic, transsolvus granite that contained primary elpidite. All of these phases share a common igneous lineage. The Baerzhe deposit is characterized by five stages of rare metal mineralization, starting with the magmatic crystallization of elpidite (stage I). Elpidite was subsequently hydrothermally replaced by zircon and quartz to form pseudomorphs in stage II. Stage II is also characterized by Na metasomatism (albite and aegirine alteration of alkali feldspar and amphibole, respectively) and by snowball quartz that contains inclusions of albite, aegirine, and zircon. Sodium metasomatism, Zr mineralization, and snowball quartz are restricted to the agpaitic rocks. REEs, Nb, and Be occur as a variety of minerals that are disseminated through all the altered rocks and were precipitated in three sequential stages (stages III-V), with the formation of heavy REE-dominant phases generally preceding light REE-dominant phases. Moderate to pervasive hematization, which altered much of the transsolvus miaskitic granite and all the agpaitic granite, initiated late in stage II and accompanied most of the REE-Nb-Be mineralization in stage III. The stage-III mineralization, represented by hingganite-(Y), hingganite-(Ce), aeschynite-(Y), and columbite-(Fe), developed in two substages, with hingganite-(Y) preceding hingganite-(Ce); these REE-Nb-Be minerals are mainly contained in quartz-rich pseudomorphs (REE-Nb-Be–rich pseudomorphs) but also occur as partial replacement of earlier minerals. Stages IV and V represent a transition from F-absent assemblages that are characterized by euxenite-group minerals and monazite-(Ce) in stage IV-A, to light REE and F-rich minerals: bastnäsite-(Ce) in stage IV-B and fluocerite-(Ce) and synchysite-(Ce) in stage V. The low REE, Nb, and Be concentrations in amphibole and the fact that REE-Nb-Be assemblages never contain zircon as a constituent preclude leaching of preexisting amphibole or zirconosilicates as significant sources of REEs, Nb, or Be. Rather, these elements may have inherently been present in magmatic-hydrothermal fluids or have been leached from crystallized fluoride melts.

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