Weak B‐Type Olivine Fabric Induced by Fast Compaction of Crystal Mush in a Crustal Magma Reservoir

2019 ◽  
Vol 124 (4) ◽  
pp. 3530-3556 ◽  
Author(s):  
Zhuosen Yao ◽  
Kezhang Qin ◽  
Qin Wang ◽  
Shengchao Xue
Keyword(s):  
Magma Reservoir ◽  
Crystal Mush ◽  
Crustal Magma

A message from the depth: the origin of the amphibole crystal clots with pyroxene cores in the Late Pleistocene Ciomadul dacites, Romania

2021 ◽  
Author(s):  
Barbara Cserép ◽  
Zoltán Kovács ◽  
Kristóf Fehér ◽  
Szabolcs Harangi
Keyword(s):  
Inner Core ◽  
Magma Mixing ◽  
Outer Part ◽  
Mafic Magma ◽  
Outer Zone ◽  
Magma Reservoir ◽  
Explosive Eruptions ◽  
Innovation Fund ◽  
Amphibole Crystal ◽  
Crustal Magma

<p>Identification of trans-crustal magma reservoir processes beneath volcanoes is a crucial task to better understand the behaviour and possible future activities of volcanic systems. Detailed petrological investigations have a fundamental role in such studies. Dacitic magmas are usually formed in an upper crustal magma reservoir by complex open-system processes including crystal fractionation and magma mixing following recharge events. Conditions of such processes are usually constrained by crystal-scale studies, whereas there is much less information about the petrogenetic processes occurring in the lower crustal hot zone. Here we provide insight into such processes by new results on amphibole crystal clots found in dacitic pumices from an explosive volcanic suite of the Ciomadul volcano, the youngest one in eastern-central Europe.</p><p>Amphibole is a common mineral phase of the Ciomadul dacites, occuring as phenocrysts and antecrysts, but occasionally they also form crystal clots with an inner core of either pyroxene or olivine with high Mg-numbers. Olivine is observed mostly in the 160-130 ka lava dome rocks, whereas the younger explosive eruption products are characterised by orthopyroxene and clinopyroxene. Such mafic crystal clots are most common in the pumices of the earliest explosive eruptions, which occurred after long quiescence at 56-45 ka. The most common appearance has high-Mg pyroxene core (mg#: 0.76-0.92) rimmed by amphibole. Two types of amphibole are found in such clots: irregular zone of actinolite to magnesio-hornblende directly around orthopyroxene and high Mg-Al pargasitic amphibole as the outer zone. Several crystal clots contain smaller amphibole crystals with diffuse transition to clinopyroxene at the inner part and complexly zoned amphibole with biotite inclusions in the outer part. These amphibole and pyroxene have lower Mg-number (< 0.80), and higher MnO content (up to 0.52 wt%) than the most common type. In both cases, amphibole could be a peritectic product of earlier-formed pyroxenes, which reacted with water-rich melt at higher and lower temperatures, respectively. Actinolite to magnesio-hornblende at the contact represents a transitional phase between pyroxene and the newly formed amphibole. In a few cases, crystal clots contain amphibole inclusions in pyroxene macrocrysts. These amphiboles have a particular composition not yet reproduced by experiments: they have high mg# (>0.86), but low tetrahedral Al (0.9-1.0 apfu) and usually high Cr content (Cr<sub>2</sub>O<sub>3</sub> is up to 0.9 wt%), similar to the orthopyroxene and clinopyroxene hosts (0.26-0.71 and 0.78-0.89 wt%, respectively). We interpret these amphiboles as an early formed liquidus phase crystallized along with pyroxene from an ultra-hydrous mafic magma. Occasionally, crystal clots are complexly zoned amphibole macrocrysts with dispersed clinopyroxene inclusions. The amphibole has a wide compositional range, usually with high Mg-Al pargasitic core. These amphiboles could have formed by peritectic reaction between clinopyroxene and a water-rich melt.</p><p>The observed mafic crystal clots in the dacites indicate the presence of strongly hydrous mafic magmas accumulated probably at the crust-mantle boundary. During mafic recharge, volatile transfer may contribute to the crystal mush rejuvenation at shallow depth and triggering explosive eruptions.</p><p>This research was financed by the Hungarian National Research, Development and Innovation Fund (NKFIH) within K135179 project.</p>

Fine-scale segmentation of the crustal magma reservoir beneath the East Pacific Rise

2013 ◽  
Vol 6 (10) ◽  
pp. 866-870 ◽  
Author(s):  
Suzanne M. Carbotte ◽  
Milena Marjanović ◽  
Helene Carton ◽  
John C. Mutter ◽  
Juan Pablo Canales ◽  
...  
Keyword(s):  
East Pacific Rise ◽  
Magma Reservoir ◽  
Fine Scale ◽  
East Pacific ◽  
Crustal Magma

scholarly journals Petrologic Reconstruction of the Tieshan Magma Plumbing System: Implications for the Genesis of Magmatic-Hydrothermal Ore Deposits within Originally Water-Poor Magmatic Systems

2020 ◽  
Vol 61 (5) ◽  
Author(s):  
Jin-Sheng Zhou ◽  
Qiang Wang ◽  
Derek A Wyman ◽  
Zhen-Hua Zhao
Keyword(s):  
Critical Role ◽  
Magma Reservoir ◽  
Ore Deposits ◽  
Plumbing System ◽  
Magma Body ◽  
Magma Plumbing System ◽  
Fundamental Information ◽  
Hydrothermal Ore Deposits ◽  
Magma Plumbing ◽  
Crustal Magma

Abstract Most genetic models for magmatic-hydrothermal ore deposits are based on the prerequisite that the parental magmas associated with mineralization are enriched in water (> ∼4 wt %). However, it has been recognized that a number of magmatic-hydrothermal ore deposits also formed within tectono-magmatic settings that produce initially water-poor magmas such as Climax-type porphyry deposits. Here, we present a detailed reconstruction of the Tieshan magma plumbing system related to skarn-porphyry Cu–Fe–Au mineralization in the Edong district, in which primitive magmas typically show water-poor features. Applications of multiple thermodynamic calibrations on various magmatic units from the Tieshan and Tonglushan deposits provide a wealth of information regarding the structure and evolution of the transcrustal magmatic system. Petrographic observations and clinopyroxene-liquid thermobarometry calculations indicate that the Tieshan magmatic-hydrothermal system was fed by a deep crustal magma reservoir. An accurate picture of the evolution of H2O within the magma plumbing system is presented using the plagioclase-liquid hygrometer in combination with the amphibole hygrometer. Three critical stages during the evolution of water within the plumbing system have been recognized, associated with H2O contents of 0·8–1·7 wt %, 2·1–2·8 wt % and 3·2–4·6 wt %, respectively. The first enrichment of water in the magmas can be attributed to the separation and transfer of evolved melts from the deep magma reservoir to the shallow crust. Continuous cooling and solidification of the shallow magma body gave rise to the second enrichment of H2O in residual melts, leading to magmas that were fertile for the formation of ore deposits. The detailed chemical evolution of the magma plumbing system was investigated using mineral trace element compositions in combination with the partition coefficients predicted by the lattice strain model. The earliest equilibrium melts are characterized by high Sr contents (the average = 658 ± 64 ppm), suggesting that high Sr/Y signatures were likely derived from their magma sources or fractionation at deeper levels in initially water-poor environments. Variations of some particular geochemical fingerprints in equilibrium melts such as, Dy/Dy* and Eu/Eu*, also provide fundamental information on the evolution of the magma plumbing system. Our study confirms the critical role of a deep crustal magma reservoir on the formation of magmatic-hydrothermal ore deposits. The fertility of magmas with respect to ore deposit formation was enhanced by the extraction and transfer of evolved magmas from the deep reservoir to shallower levels, particularly due to the enrichment of magmatic water contents. In addition, the presence of a deep magma reservoir also sustains the incremental growth of shallow magma chambers, which provide ore-forming fluids.

scholarly journals Constraints on the upper crustal magma reservoir beneath Yellowstone Caldera inferred from lake-seiche induced strain observations

2013 ◽  
Vol 40 (3) ◽  
pp. 501-506 ◽  
Author(s):  
Karen Luttrell ◽  
David Mencin ◽  
Olivier Francis ◽  
Shaul Hurwitz
Keyword(s):  
Magma Reservoir ◽  
Yellowstone Caldera ◽  
Crustal Magma

scholarly journals Time scales and temperatures of crystal storage in magma reservoirs: implications for magma reservoir dynamics

2019 ◽  
Vol 377 (2139) ◽  
pp. 20180009 ◽  
Author(s):  
Kari M. Cooper
Keyword(s):  
Time Scales ◽  
Physical State ◽  
Large Range ◽  
Numerical Models ◽  
Magma Reservoir ◽  
Radiometric Dating ◽  
Reservoir Architecture ◽  
Magma Reservoirs ◽  
Magma System ◽  
Crustal Magma

The thermal and therefore physical state of magma bodies within the crust controls the processes and time scales required to mobilize magmas before eruptions, which in turn are critical to hazard assessment. Crystal records can be used to reconstruct magma reservoir histories, and the resulting time and length scales are converging with those accessible through numerical modelling of magma system dynamics. The goal of this contribution is to summarize constraints derived from crystal chronometry (radiometric dating and modelling intracrystalline diffusion durations), in order to facilitate use of these data by researchers in other fields. Crystallization ages of volcanic minerals typically span a large range (10 4 –10 5  years), recording protracted activity in a given magma reservoir. However, diffusion durations are orders of magnitude shorter, indicating that the final mixing and assembly of erupted magma bodies is rapid. Combining both types of data in the same samples indicates that crystals are dominantly stored at near- or sub-solidus conditions, and are remobilized rapidly prior to eruptions. These observations are difficult to reconcile with some older numerical models of magma reservoir dynamics. However, combining the crystal-scale observations with models which explicitly incorporate grain-scale physics holds great potential for understanding dynamics within crustal magma reservoirs. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.

Extraction of high-silica granites from an upper crustal magma reservoir: Insights from the Narusongduo magmatic system, Gangdese arc

2020 ◽  
Vol 105 (10) ◽  
pp. 1572-1584 ◽  
Author(s):  
Jin-Sheng Zhou ◽  
Zhu-Sen Yang ◽  
Qiang Wang ◽  
Yuan-Chuan Zheng ◽  
Zeng-Qian Hou ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Magma Reservoir ◽  
Igneous Rocks ◽  
Volcanic Complex ◽  
Differentiated Products ◽  
Magmatic System ◽  
Andesitic Magma ◽  
Melt Separation ◽  
High Silica ◽  
Crustal Magma

Abstract The genesis of high-silica igneous rocks is important for understanding the behavior of shallow magmatic systems. However, although many such studies have focused on the eruption of crystal-poor high-SiO2 rhyolites, the origin of high-silica granites (HSGs) has received comparatively little attention. Here, we present a detailed study of HSGs from the Narusongduo volcanic complex, Gangdese arc. Combining zircon U-Pb geochronology with stratigraphic investigations, we show that the Narusongduo magmatic system was constructed over a period of ≥3.7 Myr with or without lulls. On the basis of zircon textures and ages, diverse zircon populations, including antecrysts and autocrysts, are recognized within the HSGs and volcanic rocks. All of the igneous rocks within the Narusongduo volcanic complex have highly radiogenic Sr–Nd isotopic compositions. Our results indicate the presence of an andesitic magma reservoir in the upper crust at a paleodepth of ~8 km. Ubiquitous zircon antecrysts in the HSGs, combined with compositional similarities between the HSGs and evolved melts of the andesitic magma reservoir, indicate that the Narusongduo HSGs represent melts extracted from the shallow magma reservoir. In addition, our results suggest that magma recharge promoted the escape of high-silica melts to form the Narusongduo HSGs. This work presents an excellent case that kilometer-scale high-silica granites are the differentiated products from an upper crustal magma reservoir. It would make a contribution to contemporary debates concerning the efficiency of crystal–melt separation in upper crustal magmatic systems.

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