Uncommon mafic rocks (MgO: >10 wt%) in the northernmost Andean volcanic chain (4° 25″ N): Implications for magma source and evolution

2021 ◽  
pp. 103308
Author(s):  
J. Velandia ◽  
H. Murcia ◽  
K. Németh ◽  
C. Borrero
Keyword(s):  
Magma Source ◽  
Mafic Rocks ◽  
Volcanic Chain

Geochronology and geochemistry of late Silurian-early Devonian mafic-ultramafic complexes in the eastern section of Qilian block, NW China: Implications for late early Paleozoic tectonic evolution of the Qilian orogeny belt

2020 ◽  
Author(s):  
Kuo-An Tung ◽  
Houng-Yi Yang ◽  
Huai-Jen Yang ◽  
Jianxin Zhang ◽  
Dunyi Liu ◽  
...  
Keyword(s):  
Country Rock ◽  
Crustal Contamination ◽  
Magma Source ◽  
Early Paleozoic ◽  
Intrusive Body ◽  
Mafic Rocks ◽  
Northern Margin ◽  
Rock Types ◽  
Two Samples ◽  
Middle Paleozoic

<p>Field relationships, mineralogy, petrology, geochemistry, geochronology, and Nd-Hf-O isotopes of the mafic-ultramafic rocks from the east part of the Qilian block are studied in the present work. The Aganzhen intrusive body only exposed in the Zhigoumen, Shiguanzi, Xianggoumen outcrops and includes Hornblende peridotite, wehrlite, olivine-bearing pyroxenite, hornblende-bearing pyroxenite, websterite, clinopyroxenite, hornblendite, olivine-bearing gabbro. The gabbroic rocks are also layered or massive cumulates with rock types varying continuously from noritic gabbro through hornblende gabbro to dioritic norite. Contact metamorphic zones are well developed between the Aganzhen intrusive body and the country rock. Major element contents of Aganzhen ultramafic-mafic rocks show subalkalic series and are characterized by low SiO<sub>2</sub> contents (38.09-54.96 %), low TiO<sub>2</sub> contents (0.09-0.72 %), low P<sub>2</sub>O<sub>5</sub> contents (0.00-0.36 %) and alkali contents (Na<sub>2</sub>O+K<sub>2</sub>O 0.01-5.35 %), but high MgO contents (9.68-33.06 %), Ni contents (116-1505 ppm), Cr contents (713-2808 ppm). Similar LREE-rich pattern ((Ce/Yb)<sub>N</sub> =0.95-3.80 except two Samples) and tiny Eu anomaly (Eu/Eu* =0.6-1.2) indicate the Aganzhen ultramafic-mafic rocks have the same magma source. Trace elements are enriched in LILE (Rb, Th, U, K), relatively depleted in HFSE (Nb and Ta), and the La/Yb, Ce/Yb, Th/Yb, Nb/La, La/Sm values suggest the limited crustal contamination during the rise of the magma. The ε<sub>Nd</sub> (430 Ma) values are −6.9–+2.5 and T<sub>DM</sub> values are 3.6–1.4 Ga. The SHRIMP ages are 433±2 Ma for the Zhigoumen websterite(101-2101A), 434±3 Ma for Shiguanzi hornblendite(101-2104A) and 412±3 Ma for the Xianggoumen serpentinite(101-2107A). In situ zircon O-Hf isotope, the δ<sup>18</sup>O compositions of vary from +9.03 to +9.50 (except three points +11.33, +12.38, +12.44) and ε<sub>Hf</sub>(t) value is +0.29 to +4.13 for the Zhigoumen pyroxenite(101-2101A), the δ<sup>18</sup>O compositions of vary from +6.39 to +7.12 and ε<sub>Hf</sub>(t) value is +7.76 to +13.26 for Shiguanzi gabbro(101-2104A), and the δ<sup>18</sup>O compositions of vary from +4.68 to +5.31 and ε<sub>Hf</sub>(t) value of +0.28 to +2.79 for the Xianggoumen serpentinite(101-2107A). According to the above datum, we suggest that middle Paleozoic magmatisms last ~20 m.y. (434-412 Ma) on the northern margin of the Qilian Block was related to the Early Paleozoic continental collision between the Qilian and Alax blocks, and to subsequent subduction and thermal underplating.</p>

scholarly journals Late Jurassic Changmar Complex from the Shyok ophiolite, NW Himalaya: a prelude to the Ladakh Arc

2020 ◽  
pp. 1-22
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Vickie C. Bennett
Keyword(s):  
Late Jurassic ◽  
Early Stage ◽  
Western Himalaya ◽  
Island Arc ◽  
Magma Source ◽  
Nw Himalaya ◽  
Volcanic Arc ◽  
Mafic Rocks ◽  
Isotopic Signatures ◽  
Enrichment Characteristics

Abstract The Shyok Suture in western Himalaya preserves a record of the opening and closure of the Mesotethys Ocean between the Shyok ophiolite and Karakoram terrane prior to the India–Eurasia collision. The formation age of the Shyok ophiolite was unknown, which impeded correlation with similar rocks along the Shyok Suture in Pakistan and corresponding sutures in Tibet. We report the first zircon U–Pb ages of a newly documented suite, here named the Changmar Complex. The Changmar Complex gabbronorite and plagiogranite yielded SHRIMP U–Pb zircon Late Jurassic ages of 159.4 ± 0.9 Ma and 151.9 ± 1.5 Ma. Their highly positive initial εHf values (+14.9 to +16.9) indicate a juvenile mantle origin, without continental crust influence on the magma source. The Shyok ophiolite represents either: (1) a separate island arc that preceded formation of the Cretaceous–Eocene Ladakh Arc; or (2) the oldest magmatism and early stage of the Ladakh Arc. Intrusive and extrusive mafic rocks from the Shyok Suture analysed in this study have typical supra-subduction zone enrichment characteristics in their geochemistry and are classified as part of the volcanic-arc ophiolite. The U–Pb age and Hf isotopic signatures for the Shyok ophiolite are similar to the Late Jurassic Matum Das tonalite within the Kohistan Arc; we therefore suggest that they are part of the same intra-oceanic island-arc system that formed in the Mesotethys Ocean prior to Late Jurassic time.

SYSTEMATIC MIDDDLE TO LATE JURASSIC CHANGES IN MAGMA SOURCE IN THE MOJAVE SEGMENT OF CALIFORNIA’S CONTINENTAL ARC

2016 ◽  
Author(s):  
Jade Star Lackey ◽  
◽  
Kyle R. McCarty ◽  
Anne A. Fulton ◽  
Juliet Ryan-Davis ◽  
...  
Keyword(s):  
Late Jurassic ◽  
Magma Source ◽  
Continental Arc

ISPY SAN CRISTOBAL'S MAGMA SOURCE: THE GALAPAGOS ISLAND EDITION

2018 ◽  
Author(s):  
Regina Pimentel ◽  
◽  
Karen Harpp ◽  
Dennis Geist ◽  
Hannah Bercovici ◽  
...  
Keyword(s):  
Magma Source ◽  
Galapagos Island

scholarly journals Critical Tectonic Limits for Geothermal Aquifer Use: Case Study from the East Slovakian Basin Rim

Resources ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 31
Author(s):  
Stanislav Jacko ◽  
Roman Farkašovský ◽  
Igor Ďuriška ◽  
Barbora Ščerbáková ◽  
Kristína Bátorová
Keyword(s):  
Heat Flow ◽  
Pannonian Basin ◽  
Open Fractures ◽  
Water Type ◽  
Geothermal Heat ◽  
The North ◽  
Heat System ◽  
Volcanic Chain ◽  
Saline Solutions

The Pannonian basin is a major geothermal heat system in Central Europe. Its peripheral basin, the East Slovakian basin, is an example of a geothermal structure with a linear, directed heat flow ranging from 90 to 100 mW/m2 from west to east. However, the use of the geothermal source is limited by several critical tectono-geologic factors: (a) Tectonics, and the associated disintegration of the aquifer block by multiple deformations during the pre-Paleogene, mainly Miocene, period. The main discontinuities of NW-SE and N-S direction negatively affect the permeability of the aquifer environment. For utilization, minor NE-SW dilatation open fractures are important, which have been developed by sinistral transtension on N–S faults and accelerated normal movements to the southeast. (b) Hydrogeologically, the geothermal structure is accommodated by three water types, namely, Na-HCO3 with 10.9 g·L−1 mineralization (in the north), the Ca-Mg-HCO3 with 0.5–4.5 g·L−1 mineralization (in the west), and Na-Cl water type containing 26.8–33.4 g·L−1 mineralization (in the southwest). The chemical composition of the water is influenced by the Middle Triassic dolomite aquifer, as well as by infiltration of saline solutions and meteoric waters along with open fractures/faults. (c) Geothermally anomalous heat flow of 123–129 °C with 170 L/s total flow near the Slanské vchy volcanic chain seems to be the perspective for heat production.

scholarly journals Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)

2021 ◽  
Vol 83 (6) ◽  
Author(s):  
Gianmaria Tortelli ◽  
Anna Gioncada ◽  
Carolina Pagli ◽  
Mauro Rosi ◽  
Laura De Dosso ◽  
...  
Keyword(s):  
Seismic Data ◽  
Volcanic Field ◽  
Lava Flows ◽  
Magmatic Activity ◽  
Magma Storage ◽  
Plumbing System ◽  
Mafic Lava ◽  
Cinder Cones ◽  
Mafic Rocks ◽  
Seismic Networks

AbstractDuring continental rifting, strain and magmatism are believed to localize to narrow magmatic segments, while the rift margin is progressively abandoned. We integrate volcanological, geochemical, petrological and seismic data from the Ma’Alalta volcanic field (MVF) near the western margin of Afar, to show that the MVF is an active magmatic segment. Magmatism in MVF initiated with lava flows and large-volume, caldera-forming ignimbrites from a central edifice. However, the most recent magmatic activity shifted towards mafic lava fields, cinder cones and obsidian-rich silicic domes erupted from vents aligned NNW-SSE, defining a ~ 35-km-long magmatic segment. Along the same area, a NNW-SSE alignment of earthquakes was recorded by two local seismic networks (2005–2009 and 2011–2013). The geochemistry of the mafic rocks is similar to those of nearby axial volcanoes. Inferred magma storage depth from mineral geobarometry shows that a shallow, silicic chamber existed at ~ 5-km depth below the stratovolcano, while a stacked plumbing system with at least three magma storage levels between 9 and 24 km depth fed the recent basalts. We interpret the wide set of observations from the MVF as evidence that the area is an active magmatic segment, showing that localised axial extension can be heavily offset towards the rift margin.

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