scholarly journals Geochemical Insights From Clinopyroxene Phenocrysts Into the Magma Evolution of an Alkaline Magmatic System From the Sanshui Basin, South China

2021 ◽  
Author(s):  
Peijia Chen ◽  
Nianqiao Fang ◽  
Xiaobo Yuan
Keyword(s):  
Fractional Crystallization ◽  
South China ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Magma Ascent ◽  
Magmatic Evolution ◽  
The South ◽  
Magma Evolution ◽  
Magma Plumbing System ◽  
Magma System

The Sanshui Basin (SSB) is located at the northern continental margin of the South China Sea and characterized by a continental rift basin. The bimodal volcanic rocks in SSB record the early Cenozoic magmatic activity in the South China Block, on the magmatic evolution process of bimodal volcanic rocks are poorly understood. Clinopyroxenes in bimodal volcanic rocks in the SSB provide an opportunity to investigate the magma process during magma ascent. We classified nine types of clinopyroxene phenocrysts according to the different compositions and textures types in cogenetic basalt-trachyandesite-comenditic trachyte, the composition of unzoned clinopyroxene have an evolution sequence of diopside- hedenbergite- aegirine with the decrease of Mg#, and the trace element contents of unzoned clinopyroxenes also increase systematically during magma evolution, indicating that the genesis of clinopyroxene dominated by fractional crystallization in a closed magma system; however, the clinopyroxenes with reverse zoning and multiple zoning record the process of magma mixing and recharge indicating an open magma system. Whilst fractional crystallization is the dominated process, magma mixing, recharge, and crystal settling complicate magma evolution. Thermobarometric calculations show that clinopyroxene phenocrysts in bimodal volcanic rocks of SSB are distributed in the whole crust during magma ascent. We have established a magma plumbing system, which provides a new constrain for the complex magmatic evolution history in the SSB by detailed mineral-scale analysis.

scholarly journals Geochemical Insights from Clinopyroxene Phenocrysts into the Magma Evolution of an Alkaline Magmatic System from the Sanshui Basin, South China

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1295
Author(s):  
Peijia Chen ◽  
Nianqiao Fang ◽  
Xiaobo Yuan
Keyword(s):  
Fractional Crystallization ◽  
South China ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Magma Ascent ◽  
The South ◽  
Magma Evolution ◽  
Magma Plumbing System ◽  
Magma System ◽  
Structural Levels

The Sanshui Basin is located at the northern continental margin of the South China Sea and characterized by a continental rift basin. The bimodal volcanic rocks in Sanshui Basin record the early Cenozoic magmatic activity in the South China Block, but the magmatic evolution that produced the bimodal volcanic rocks is poorly understood. Clinopyroxenes in bimodal volcanic rocks in the Sanshui Basin provide an opportunity to investigate magma during magma ascent. In this work, we classified nine types of clinopyroxene phenocrysts according to composition and texture in cogenetic basalt-trachyandesite-comenditic trachyte, while the composition of unzoned clinopyroxene have an evolution sequence of diopside-hedenbergite-aegirine along with an increase in trace element contents with a decrease of Mg#, indicating that the genesis of clinopyroxene was dominated by fractional crystallization in a closed magma system. However, the clinopyroxenes with reversed zoning and multiple zoning record the process of magma mixing and recharge indicating an open magma system. While fractional crystallization is the dominant process, magma mixing, recharge, and crystal settling were also found to influence magma evolution. Thermobarometric calculations showed that clinopyroxene crystallized a several structural levels in the crust during magma ascent. In this study, we established a magma plumbing system that provides new constraints for the magma evolution in the Sanshui Basin.

Relative roles of source composition, fractional crystallization and crustal contamination in the petrogenesis of Andean volcanic rocks

1984 ◽  
Vol 310 (1514) ◽  
pp. 675-692 ◽  
Keyword(s):  
Subduction Zone ◽  
Continental Crust ◽  
Fractional Crystallization ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Oceanic Lithosphere ◽  
Alkaline Basalt ◽  
Complex Process ◽  
Heterogeneous Mantle

There are well established differences in the chemical and isotopic characteristics of the calc-alkaline basalt—andesite-dacite-rhyolite association of the northern (n.v.z.), central (c.v.z.) and southern volcanic zones (s.v.z.) of the South American Andes. Volcanic rocks of the alkaline basalt-trachyte association occur within and to the east of these active volcanic zones. The chemical and isotopic characteristics of the n.v.z. basaltic andesites and andesites and the s.v.z. basalts, basaltic andesites and andesites are consistent with derivation by fractional crystallization of basaltic parent magmas formed by partial melting of the asthenospheric mantle wedge containing components from subducted oceanic lithosphere. Conversely, the alkaline lavas are derived from basaltic parent magmas formed from mantle of ‘within-plate’ character. Recent basaltic andesites from the Cerro Galan volcanic centre to the SE of the c.v.z. are derived from mantle containing both subduction zone and within-plate components, and have experienced assimilation and fractional crystallization (a.f.c.) during uprise through the continental crust. The c.v.z. basaltic andesites are derived from mantle containing subduction-zone components, probably accompanied by a.f.c. within the continental crust. Some c.v.z. lavas and pyroclastic rocks show petrological and geochemical evidence for magma mixing. The petrogenesis of the c.v.z. lavas is therefore a complex process in which magmas derived from heterogeneous mantle experience assimilation, fractional crystallization, and magma mixing during uprise through the continental crust.

scholarly journals Multi-stage arc magma evolution recorded by apatite in volcanic rocks

Geology ◽  
2020 ◽  
Vol 48 (4) ◽  
pp. 323-327 ◽  
Author(s):  
Chetan L. Nathwani ◽  
Matthew A. Loader ◽  
Jamie J. Wilkinson ◽  
Yannick Buret ◽  
Robert H. Sievwright ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Explosive Volcanism ◽  
Ore Deposits ◽  
Magma Evolution ◽  
Arc Magmas ◽  
Deep Crust ◽  
Multi Stage ◽  
Novel Approach ◽  
Arc Magma

Abstract Protracted magma storage in the deep crust is a key stage in the formation of evolved, hydrous arc magmas that can result in explosive volcanism and the formation of economically valuable magmatic-hydrothermal ore deposits. High magmatic water content in the deep crust results in extensive amphibole ± garnet fractionation and the suppression of plagioclase crystallization as recorded by elevated Sr/Y ratios and high Eu (high Eu/Eu*) in the melt. Here, we use a novel approach to track the petrogenesis of arc magmas using apatite trace element chemistry in volcanic formations from the Cenozoic arc of central Chile. These rocks formed in a magmatic cycle that culminated in high-Sr/Y magmatism and porphyry ore deposit formation in the Miocene. We use Sr/Y, Eu/Eu*, and Mg in apatite to track discrete stages of arc magma evolution. We apply fractional crystallization modeling to show that early-crystallizing apatite can inherit a high-Sr/Y and high-Eu/Eu* melt chemistry signature that is predetermined by amphibole-dominated fractional crystallization in the lower crust. Our modeling shows that crystallization of the in situ host-rock mineral assemblage in the shallow crust causes competition for trace elements in the melt that leads to apatite compositions diverging from bulk-magma chemistry. Understanding this decoupling behavior is important for the use of apatite as an indicator of metallogenic fertility in arcs and for interpretation of provenance in detrital studies.

The Pliocene volcanic rocks of Crommyonia, western Greece and their implications for the early evolution of the South Aegean arc

1997 ◽  
Vol 134 (1) ◽  
pp. 55-66 ◽  
Author(s):  
GEORGIA PE-PIPER ◽  
K. HATZIPANAGIOTOU
Keyword(s):  
Volcanic Rocks ◽  
The South ◽  
The West ◽  
Magma Evolution ◽  
Volcanic Arc ◽  
Nd Isotope ◽  
Arc Volcanism ◽  
Lava Domes ◽  
Aegean Arc ◽  
Western Greece

Minor Pliocene dacites from Crommyonia mark the western end of the South Aegean volcanic arc. They form small lava domes and flows generally associated with extensional faults. An older group (3.6–4 Ma) occurs in the west and a younger group (2.3–2.8 Ma) in the east. Volcanic rocks of similar age are found at Aegina, Poros and Milos in the western part of the South Aegean arc, whereas volcanism in the eastern part of the arc is of Quaternary age. The two groups of rocks at Crommyonia are chemically distinct. Both groups contain multiple generations of plagioclase. Both have εNd (−8.0 to −10.6) that is much more negative than any other rocks in the South Aegean arc and model ages that are similar to those for many Miocene extensional granites of the Cyclades. The model ages are interpreted to reflect a mid-Proterozoic mantle event recognized elsewhere in the Hellenides. The Crommyonia dacitic magmas represent the first stages of melting of deep lithosphere as a result of both subduction-related hydrous fluids and extensional decompression. Plagioclase compositions suggest important magma evolution in a base-of-crust magma chamber, where the strong crustal Nd isotope signature was acquired. With time, asthenospheric sources that upwelled as a result of extension played an increasingly important role in determining the isotopic characteristics of the arc volcanism.

scholarly journals Plagioclase Hosted Melt Inclusion in Hypabyssal Rocks in Torud-Ahmad Abad Magmatic Belt

2019 ◽  
Vol 55 (1) ◽  
pp. 158
Author(s):  
Fazilat Yousefi ◽  
Lambrini Papadopoulou ◽  
Mahmoud Sadeghian ◽  
Christina Wanhainen ◽  
Glenn Bark
Keyword(s):  
Melt Inclusions ◽  
Melt Inclusion ◽  
Magma Mixing ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Sem Analysis ◽  
Magma Evolution ◽  
Compositional Evolution ◽  
Growth Zones ◽  
First Time

This study investigates for the first time melt inclusions (MI) that are found within fundamental minerals of subvolcanic rocks in Torud-Ahmad Abad magmatic belt. The Torud-Ahmad Abad magmatic belt is situated in south-southeast of Shahrood and belongs to the northern part of central Iran structural zone. Melt inclusions represent liquids that were trapped along growth zones (primary) or healed fractures of mineral phases, which crystallized from the silicate liquid as it cooled. Based on SEM analysis of these melt inclusions, their compositions are dacite, andesite and basaltic andesite. Thus, with the use of melt inclusions in the volcanic rocks of Torud-Ahmad Abad magmatic belt, we attempt to show the compositional evolution and origin of magma. The effective factors on magma evolution are magma mixing, fractional crystallization and crustal contamination.

Timescales of magma mixing in the magma plumbing system of Bezymianny volcano: insights from diffusion chronometry

2018 ◽  
pp. 52-58
Author(s):  
V. O. Davydova ◽  
V. D. Shcherbakov ◽  
P. Yu. Plechov
Keyword(s):  
Magma Mixing ◽  
Mafic Magma ◽  
Plumbing System ◽  
Magma Evolution ◽  
Bezymianny Volcano ◽  
Magma Plumbing System ◽  
Diffusion Chronometry ◽  
Shallow Magma Chamber ◽  
Trigger Mechanisms ◽  
Magma Plumbing

Zoned crystals record changes in magma evolution, such as injection of mafic magma into a shallow magma chamber, which often triggered to eruption of arc volcanoes. We applied diffusion chronometry for reverse zoned crystals of orthopyroxene from 6 eruptions of Bezymianny volcano during 2006–2012 years and showed correlation between time of injection of new magma and recorded seismicity. We descripted two type of Bezymianny volcano eruptions, which driven by different trigger mechanisms: 1) orthopyroxene rims formed during up to 3 years previous to eruption; 2) orthopyroxene rims formed during 0–2 months previous to eruption.

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