Open-System Magma Chamber Evolution: an Energy-constrained Geochemical Model Incorporating the Effects of Concurrent Eruption, Recharge, Variable Assimilation and Fractional Crystallization (EC-E'RA FC)

The Flavrian pluton is a sill-shaped intrusion in the Blake River Group (BRG) volcanic rocks in the Noranda region of the Abitibi greenstone belt. The pluton is dominated by trondhjemites and tonalites, with minor peripheral quartz gabbro and hybrid phases. The BRG volcanic rocks consist of a bimodal suite of basalt–andesite and rhyolite. The Flavrian trondhjemites are geochemically identical to the rhyolitic lavas of the BRG (SiO2 ≥ 72%, La/Sm = 3.4, La/Yb = 3.6, Zr/Y = 3.9, Y/Nb = 3.1), and the Flavrian gabbroic and dioritic rocks are identical to the BRG basalts and andesites (SiO2 < 58%, La/Sm = 3.0, La/Yb = 5.5, Zr/Y = 4.2, Y/Nb = 3.3). However, the tonalitic rocks of the Flavrian pluton have no extrusive equivalents in the BRG. The different compositional spectra of the extrusive and intrusive rocks are interpreted as being a result of a transition in magma-chamber evolution from a zoned open system that was active during the evolution of the volcanic rocks to closed-system plutonic crystallization. The latter destroyed the compositional bimodality of the magma chamber and resulted in the evolution of intermediate compositions (tonalites) generated by both fractional crystallization and magma mixing.

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Energy-Constrained Open-System Magmatic Processes I: General Model and Energy-Constrained Assimilation and Fractional Crystallization (EC-AFC) Formulation

Journal of Petrology ◽

10.1093/petrology/42.5.999 ◽

2001 ◽

Vol 42 (5) ◽

pp. 999-1018 ◽

Cited By ~ 257

Author(s):

F. J. SPERA

Keyword(s):

Fractional Crystallization ◽

Open System ◽

General Model ◽

Magmatic Processes ◽

Energy Constrained

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The role of shallow open system processes in the evolution of South Tepeldag Pluton (NW Turkey): insights and constraints from thermodynamic modelling

10.5194/egusphere-egu21-13662 ◽

2021 ◽

Author(s):

Tunahan Arık ◽

Ömer Kamacı ◽

Işıl Nur Güraslan ◽

Şafak Altunkaynak

Keyword(s):

Fractional Crystallization ◽

Open System ◽

Suture Zone ◽

Thermodynamic Simulations ◽

Nw Turkey ◽

Microgranular Enclaves ◽

Mafic Microgranular Enclaves ◽

Ophiolitic Rocks ◽

Compositional Variations ◽

Spider Diagrams

Eocene granitoids in NW Anatolia occurred following the continental collision between Sakarya Continent and Tauride-Anatolide Platform and mark the onset of post-collisional magmatism in the region. One of the representative members of the Eocene granitoids, the Tepelda&#287; pluton crops out as two isolated granitic bodies and is intruded into the Cretaceous blueschist assemblages (Kocasu formation) and ophiolitic rocks within the Izmir-Ankara-Erzincan suture zone (IAESZ). South Tepelda&#287; pluton (STP) is composed mainly of granodiorite with subordinate quartz diorite, which show transitional contacts. Aplitic dykes crosscut the pluton as well as the country rocks. STP includes a number of mafic microgranular enclaves (MME) of gabbro/diorite composition.Geochemically, STP shows distinct I-type affinity with a metaluminous to slightly peraluminous (ASI &#8804;1.02) nature. The samples are medium-K to high-K calc-alkaline in character. They exhibit depletion in HFSE (Ti, Hf, Zr, Nb and Ta) compared to large ion lithophile elements (Rb, Ba, Th, U, K) and presents negative Nb, P, Ti anomalies. STP displays slight negative Eu anomalies (Eu/Eu* = 0.7&#8211;1.2), enrichment in LREE and flat HREE patterns in chondrite-normalized spider diagrams. MELTS modeling (with initial parameters of 1&#8211;3 kbar pressure, 2&#8211;3% water and QFM-NNO oxygen fugacity buffers) indicate that compositional variations in STP samples can be interpreted as a result of open system processes (assimilation fractional crystallization) rather than a reflection of fractional crystallization in the upper crustal magma chamber. All thermodynamic simulations dictate a crustal assimilation, especially in the late stages of the magmatic process, with a MgO, Na2O and Al2O3-rich assimilant similar to the suture zone (IAESZ) rocks.

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The Skye Main Lava Series: liquid density and the absence of basaltic hawaiites

Geological Magazine ◽

10.1017/s001675680000697x ◽

1989 ◽

Vol 126 (6) ◽

pp. 681-684 ◽

Cited By ~ 3

Author(s):

A. C. Cattell

Keyword(s):

Fluid Dynamics ◽

Magma Chamber ◽

Fractional Crystallization ◽

Liquid Density ◽

Critical Factors ◽

Density Maximum ◽

Ti Oxides ◽

Rock Column ◽

Strong Control

AbstractBasaltic hawaiite lavas are virtually absent in the Eocene Skye Main Lava Series, in contrast to relatively abundant basalts and hawaiites. Fractional crystallization from basalt to basaltic hawaiite involves extraction of a large proportion of plagioclase, and liquid densities thereby increase. From basaltic hawaiite to hawaiite titanomagnetite is a significant fractionating phase, and liquid densities decline. The coincidence between a gap in erupted compositions and a density maximum implies that liquid density exerted a strong control on ‘eruptibility’ of magmas; basaltic hawaiites were too dense to be erupted. Density maxima occur in basalt suites if plagioclase fractionates before Fe–Ti oxides, and may explain compositional gaps in erupted magmas. Compositional gaps are not the inevitable result of density maxima; the density of the rock column above, and the fluid dynamics within, the magma chamber where differentiation occurs are also critical factors.

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