Mineral chemistry of igneous melanite garnets from analcite-bearing volcanic rocks, Alberta, Canada

Abstract The ∼50 km long Rosario segment of the Cretaceous Alisitos oceanic arc terrane provides undeformed three-dimensional exposures of the upper 7 km of an oceanic extensional arc, where crustal generation processes are recorded in both the volcanic and underlying plutonic rocks. These exceptional exposures allow for the study of the physical and chemical links between the rock units and help constrain the differentiation processes active during the growth and evolution of arc crust. This study focuses on the southern third of the Rosario segment, previously referred to as the southern volcano-bounded basin, and its plutonic underpinnings. Upper crustal rocks in the Rosario segment consist of a 3–5 km thick volcanic–volcaniclastic section with hypabyssal intrusions. Plutons intrude these units at various levels along-strike, but at each intrusive contact the transition is complete over a distance of <150 m, where stoped volcanic blocks are present. There is striking compositional overlap in whole-rock and mineral chemistry between the plutonic and volcanic units, suggesting a comagmatic source. Whole-rock geochemistry shows coherent trends in major and trace elements in mafic to intermediate compositions, but less coherent trends above 63 wt % SiO2. Units are predominantly low-K with flat rare earth element patterns, and show large ion lithophile element enrichment and high field strength element depletion. Initial Nd and Pb isotope ratios overlap for all units and imply no cratonic continental involvement. This agrees with low Sr/Y ratios of all rock types, indicative of thin, immature oceanic arc crust. Modeling results show that closed-system fractional crystallization drove crustal differentiation from mafic to intermediate compositions, but open-system processes likely occurred to produce some of the felsic compositions. Differentiation occurred in a two-step fractionation process. Step 1, from basaltic andesite to andesite, fractionated an anhydrous gabbroic cumulate (∼40% crystallization). Step 2, from andesite to rhyolite, fractionated a hydrous amphibole cumulate (∼65% crystallization, total), which is similar to what fluid dynamical models suggest for production of rhyolite (between 50–70% crystallization). Our results can be used as a reference model for differentiation processes relating to the growth of the middle and upper crust within active extensional arc systems. The Rosario segment plutonic rocks may be analogous to the low-velocity zone (Vp = 6·0–6·5 km s–1) imaged within the extensional Izu–Bonin arc. The chemistry of the plutonic and volcanic rocks is most similar to those of volcanic rocks in the Izu–Bonin active rift.

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Mineral chemistry of barium- and titanium-bearing biotites in calc-alkaline volcanic rocks from the Mezitler area (Balikesir-Dursunbey), western Turkey.

GEOCHEMICAL JOURNAL ◽

10.2343/geochemj.36.563 ◽

2002 ◽

Vol 36 (6) ◽

pp. 563-580 ◽

Cited By ~ 9

Author(s):

Fuat Yavuz ◽

Ali Haydar Gültekin ◽

Yüksel Örgün ◽

Nurgül Çelik ◽

Muazzez Çelik Karakaya ◽

...

Keyword(s):

Volcanic Rocks ◽

Mineral Chemistry ◽

Calc Alkaline ◽

Western Turkey

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Polyphase tectonothermal events recorded in metamorphic basement rocks from the northern Altyn Tagh, southeastern Tarim Craton

10.5194/egusphere-egu2020-3195 ◽

2020 ◽

Author(s):

Zhongmei Wang ◽

Chunming Han ◽

Wenjiao Xiao ◽

Patrick Asamoah Sakyi

Keyword(s):

Tectonic Setting ◽

Volcanic Rocks ◽

Mineral Chemistry ◽

Metasedimentary Rocks ◽

Exposed Rock ◽

Altyn Tagh ◽

Argillaceous Rocks ◽

Southeastern Margin ◽

Minimum Age ◽

Tarim Craton

&#160; Paleoproterozoic is a pivotal time for understanding the geochronological framework of the Tarim Craton. Located on the southeastern margin of the Tarim Craton, the northern Altyn Tagh is the main exposed region for Paleoproterozoic magmatic-metamorphic rocks. These rocks are diverse, diachronous and modified by multiple magmatic and/or metamorphic events. In this study, we performed systematic analyses on the amphibolite, felsic gneisses, and metasedimentary rocks in the Aketashitage area, southeastern Tarim Craton, including petrography, mineral chemistry, and whole-rock geochemistry, as well as in-situ zircon U-Pb ages and Hf isotopes, to examine the Paleoproterozoic magmatic-metamorphic events in the northern Altyn Tagh. Geochemically, the amphibolite and felsic gneisses in the Aketashitage area seemingly represent the typical bimodal associations of mafic and acidic volcanic rocks. In addition, the felsic gneisses are characterized by high Sr and low Y contents, with high Sr/Y and LaN/YbN ratios, and indistinctive Eu anomalies, closely resembling high-SiO2 adakites derived from subducted basaltic slab-melt. The palimpsest textures and geochemical features of the Aketashitage metasedimentary rocks suggest that their protoliths are argillaceous rocks. The amphibolite has a metamorphic age of 1.96 Ga, and the felsic gneisses yield crystallization ages of 2.54-2.52 Ga. For the metasedimentary rocks, the major age peaks of 2.72 Ga, 2.05 Ga and 1.97 Ga are consistent with the magmatic and/or metamorphic events in the study area. The minimum age peak suggests that the depositional age is no earlier than 1.97 Ga. The geochemical and geochronological evidences documented by the exposed rock associations in the Aketashitage area suggest a subduction-related tectonic setting in the Paleoproterozoic. Our new data combined with the previous studies indicate that the Paleoproterozoic magmatism and metamorphism in the northern Altyn Tagh area are nearly synchronous, and both are likely related to oceanic subduction.

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MINERALOGICAL, PETROLOGICAL AND GEOCHEMICAL FEATURES OF THE UNIQUE LAPIS LACEDAEMONIUS (KROKEATIS LITHOS) FROM LACONIA, GREECE: APPROACH ON PETROGENETIC PROCESSES WITHIN THE TRIASSIC VOLCANIC CONTEXT

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.14235 ◽

2017 ◽

Vol 50 (4) ◽

pp. 1903

Author(s):

P. Koutsovitis ◽

C. Kanellopoulos ◽

S. Passa ◽

K. Foni ◽

E. Tsapara ◽

...

Keyword(s):

Volcanic Rock ◽

Volcanic Rocks ◽

Mineral Chemistry ◽

Coarse Grained ◽

Geochemical Analysis ◽

Calc Alkaline ◽

Rock Outcrops ◽

Volcanic System ◽

Chemistry Data ◽

Historical Importance

The Lapis Lacedaemonius (krokeatis lithos) is a well-known meta-volcanic rock of great historical importance. Petrographic observations, mineral chemistry data, as well as geochemical analysis of selected samples, reveal that these rocks are porphyritic metabasaltic rocks which have been significantly affected by saussuritization and also by restricted silicification processes. They represent subduction related calc-alkaline volcanic rocks which also appear in the adjacent Hellenic Triassic volcanic outcrops, and appear to be associated with the rift/drift phase within the Pindos oceanic realm. The unique features of the Lapis Lacedaemonius, when compared to geochemically similar volcanic rock outcrops, are mainly attributed to their distinct porphyritic textures, predominantly with microlithically textured groundmass along with the coarse grained plagioclase, and to saussuritization processes. The Lapis Lacedaemonius seems to have been formed in a sub-volcanic system closely associated with epidosites, suggesting that metasomatism occurred within hydrothermal upflow zones.

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Mineral Chemistry and Thermobarometry of the Volcanic Rocks in Torud, Iran

Open Journal of Geology ◽

10.4236/ojg.2014.49033 ◽

2014 ◽

Vol 04 (09) ◽

pp. 425-435

Author(s):

Elham Shah Hosseini ◽

Afshin Ashja Ardalan ◽

Mohammad Hashem Emami ◽

Mohammad Hossein Razavi

Keyword(s):

Volcanic Rocks ◽

Mineral Chemistry

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Major and trace-element mineral chemistry and implications for the petrogenesis of Eocene alkaline volcanic rocks from the western Rio Grande Rise, South Atlantic Ocean

10.7185/gold2021.6348 ◽

2021 ◽

Author(s):

Julia Guerra ◽

Valdecir Janasi ◽

Priyeshu Srivastava ◽

Miguel Basei ◽

Luigi Jovane

Keyword(s):

Atlantic Ocean ◽

Trace Element ◽

Volcanic Rocks ◽

Rio Grande ◽

Mineral Chemistry ◽

South Atlantic ◽

South Atlantic Ocean

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Mineral Chemistry of Forearc Volcanic Rocks from the Izu-Bonin Arc, Holes 792D and 793B

10.2973/odp.proc.sr.126.147.1992 ◽

1992 ◽

Cited By ~ 1

Author(s):

H. Lapierre ◽

R.N. Taylor ◽

O. Rouer ◽

H. Chaisemartin

Keyword(s):

Volcanic Rocks ◽

Mineral Chemistry

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Reconstruction of the Jurassic to Early Cretaceous tectono-magmatic evolution of the Northern Andean Arc from their Crustal Thickness and Thermobarometry

10.5194/egusphere-egu21-10222 ◽

2021 ◽

Author(s):

Luisa Chavarria ◽

Camilo Bustamante ◽

Agustín Cardona ◽

Germán Bayona

Keyword(s):

Early Cretaceous ◽

Deep Level ◽

Thermal Flux ◽

Volcanic Rocks ◽

Mineral Chemistry ◽

Crustal Thickness ◽

First Episode ◽

Magma Source ◽

Northern Andes ◽

Last Stage

Igneous rocks in magmatic arcs record variations in composition, thermal flux, and subduction dynamics through time. In the Northern Andes, arc magmatism of the Jurassic age registers a complicated history, including the fragmentation of Pangea at the end of the Triassic and the beginning of a new subduction zone in the Jurassic located at the western margin of South America.We characterized the crustal thickness variations of the Early Jurassic to Early Cretaceous (194-130 Ma) in plutonic and volcanic rocks of the Northern Andes of Colombia and Ecuador, using trace elements signatures and analyzed the implications of the emplacement conditions during the last stage of the magmatism using Al-in-hornblende thermobarometry and mineral chemistry. Moderate rare earth elements (REE) slopes and depleted heavy REE patterns show that the primary residual magma source was amphibole, but plagioclase and pyroxene were also significant residual phases indicating that the magma source was formed in a crust that varied in thickness from 35-50 km. The La/Yb and Sr/Y crustal quantifications variations indicate that the arc underwent two thickening episodes. The first episode (190 to 180 Ma) is associated with a magmatic event. The second episode (165 to 154 Ma) is related to the shift to an oblique subduction setting and a subsequent collisional event that produced medium P-T metamorphic rocks. In the Late Jurassic to Early Cretaceous (154-130 Ma), the crust became thinner and, in this scenario, was emplaced the last stage of plutonism with depths that varied from shallow to deep level (until 25.5 km) in the crust.

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