The deep crust in convergent and divergent terranes: Laramide uplifts and basin-range rifts

1986 ◽  
pp. 243-256 ◽  
Author(s):  
George A. Thompson ◽  
Janice L. Hill
Keyword(s):  
Deep Crust

Flow of Devonian anatectic crust in the accretionary Altai Orogenic Belt, central Asia: Insights into horizontal and vertical magma transfer

2021 ◽  
Author(s):  
Sheng Wang ◽  
Yingde Jiang ◽  
Roberto Weinberg ◽  
Karel Schulmann ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Crustal Thickening ◽  
Drainage Network ◽  
Vertical Flow ◽  
Granite Emplacement ◽  
Deep Crust ◽  
Gradual Evolution ◽  
Mass Redistribution ◽  
Granite Complex ◽  
Crustal Differentiation

Flow of partially molten crust is a key contributor to mass and heat redistribution within orogenic systems, however, this process has not yet been fully understood in accretionary orogens. This issue is addressed in a Devonian migmatite-granite complex from the Chinese Altai through structural, petrological, and geochronological investigations presented in this study. The migmatite-granite complex records a gradual evolution from metatexite, diatexite to granite and preserves a record of two main Devonian phases of deformation designated D1 and D2. The D1 phase was subdivided into an early crustal thickening episode (D1B) and a later extensional episode (D1M) followed by D2 upright folding. The D1M episode is associated with anatexis in the deep crust. Vertical shortening, associated with D1M, gave rise to the segregation of melt and formation of a sub-horizontal layering of stromatic metatexite. This fabric was reworked by the D2 deformation associated with the migration of anatectic magma in the cores of F2 antiforms. Geochronological investigations combined with petro-structural analysis reveal that: (1) D1M partial melting started probably at 420−410 Ma and formed sub-horizontal stromatic metatexites at ∼30 km depth; (2) The anatectic magma accumulated and migrated when a drainage network developed, as attested by the pervasive formation of massive diatexite migmatites, at 410−400 Ma; (3) Soon after, massive flow of the partially molten crust from orogenic lower to orogenic upper crustal levels, assisted by the interplay between D2 upright folding and magma diapirism, led to migmatite-granite emplacement in the cores of regional F2 antiforms that lasted until at least 390 Ma; (4) a terminal stage was manifested by the emplacement of 370−360 Ma granite dykes into the surrounding metamorphic envelope. We propose that Devonian anatexis assisted by deformation governed first the horizontal and then the vertical flow of partially molten orogenic lower crust, which drove crustal flow, mass redistribution, and crustal differentiation in the accretionary system of the Chinese Altai.

Significance of composite lineations in the mid- to deep crust: a case study from the North Cascades, Washington

2006 ◽  
Vol 28 (2) ◽  
pp. 302-322 ◽  
Author(s):  
Robert B. Miller ◽  
Scott R. Paterson ◽  
Hermann Lebit ◽  
Helge Alsleben ◽  
Catalina Lüneburg
Keyword(s):  
North Cascades ◽  
The North ◽  
Deep Crust

Accelerated hydration of the Earth's deep crust induced by stress perturbations

Nature ◽  
2000 ◽  
Vol 408 (6808) ◽  
pp. 75-78 ◽  
Author(s):  
Bjørn Jamtveit ◽  
Håkon Austrheim ◽  
Anders Malthe-Sørenssen
Keyword(s):  
Deep Crust

scholarly journals Carbon dioxide, bicarbonate and carbonate ions in aqueous solutions under deep Earth conditions

2020 ◽  
Vol 22 (19) ◽  
pp. 10717-10725
Author(s):  
Riccardo Dettori ◽  
Davide Donadio
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solutions ◽  
Upper Mantle ◽  
Crust And Upper Mantle ◽  
Effect Of Pressure ◽  
Deep Crust ◽  
Carbonate Ions ◽  
Deep Earth ◽  
Thermodynamic Conditions

We investigate the effect of pressure, temperature and acidity on the composition of water-rich carbon-bearing fluids under thermodynamic conditions that correspond to the Earth's deep crust and upper mantle.

Triassic rejuvenation of unexposed Archean-Paleoproterozoic deep crust beneath the western Cathaysia block, South China

2018 ◽  
Vol 724-725 ◽  
pp. 65-79 ◽  
Author(s):  
Xi-Yao Li ◽  
Jian-Ping Zheng ◽  
Qing Xiong ◽  
Xiang Zhou ◽  
Lu Xiang
Keyword(s):  
South China ◽  
Deep Crust ◽  
Cathaysia Block

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.

scholarly journals Analysis of Spatiotemporal variations in mid-upper tropospheric methane during the Wenchuan Ms8.0 earthquake by three indices

2019 ◽  
Author(s):  
Jing Cui ◽  
Xuhui Shen
Keyword(s):  
Methane Concentration ◽  
Vertical Direction ◽  
Background Field ◽  
Gradient Index ◽  
Average Increase ◽  
Longmenshan Fault Zone ◽  
Deep Crust ◽  
Distribution Features ◽  
Before And After ◽  
Longmenshan Fault

Abstract. This research studied the spatiotemporal variation in methane in the mid-upper troposphere during the Wenchuan earthquake (12 May, 2008) using AIRS retrieval data and discussed the methane anomaly mechanism. Three indices were proposed and used for analysis. Our results show that the methane concentration increased significantly in 2008, with an average increase of 5.12 * 10−8, compared to the average increase of 1.18 * 10−8 in the previous five years. The Alice and Diff indices can be used to identify methane concentration anomalies. The two indices showed that the methane concentration distribution before and after the earthquake broke the distribution features of the background field. As the earthquake approached, areas of high methane concentration gradually converged towards the west side of the epicenter from both ends of the Longmenshan fault zone. Moreover, a large anomalous area was centered at the epicenter eight days before the earthquake occurred, and a trend of strengthening, weakening and strengthening appeared over time. The Gradient index showed that the vertical direction obviously increased before the main earthquake, and the value was positive. The gradient value is negative during coseismic or postseismic events. The gradient index reflects the gas emission characteristics to some extent. We also determined that the methane release was connected with the deep crust-mantle stress state, as well as microfracture generation and expansion. However, due to the lack of any technical means to accurately identify the source and content of methane in the atmosphere before the earthquake, an in-depth discussion has not been conducted, and further studies on this issue may be needed.

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