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| Verfasst von: | Angeles De La Torre, Carlos A. [VerfasserIn]  |
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| | Schmitt, Axel Karl [VerfasserIn] |
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| | Lovera, Oscar M. [VerfasserIn] |
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| | Gassert, Henja [VerfasserIn] |
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| | Gerdes, Axel [VerfasserIn] |
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| | Harvey, Janet C. [VerfasserIn] |
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| Titel: | A common magma source for plutonic and volcanic rocks of The Geysers geothermal field, California |
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| Titelzusatz: | volume and intrusive history derived from zircon |
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| Verf.angabe: | Carlos A. Angeles-De La Torre, Axel K. Schmitt, Oscar M. Lovera, Henja Gassert, Axel Gerdes, Janet C. Harvey |
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| E-Jahr: | 2023 |
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| Jahr: | 17 March 2023 |
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| Umfang: | 15 S. |
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| Fussnoten: | Online verfügbar 13. März 2023, Artikelversion 17. März 2023 ; Gesehen am 25.04.2023 |
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| Titel Quelle: | Enthalten in: Chemical geology |
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| Ort Quelle: | New York, NY [u.a.] : Elsevier, 1966 |
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| Jahr Quelle: | 2023 |
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| Band/Heft Quelle: | 624(2023) vom: März, Artikel-ID 121414, Seite 1-15 |
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| ISSN Quelle: | 1872-6836 |
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| Abstract: | The Geysers Plutonic Complex (GPC) in the California Coast Ranges underlies one of the world's premier geothermal resources. The GPC consists of three major intrusive phases, orthopyroxene-biotite microgranite porphyry, orthopyroxene-biotite granite, and hornblende-biotite-orthopyroxene granodiorite (in sequence of emplacement). These are nearly coeval and compositionally equivalent to lavas of the overlying Cobb Mountain Volcanic Center which includes (from older to younger) rhyolite of Alder Creek, dacite of Cobb Mountain, and dacite of Cobb Valley. Zircon from GPC plutonic and associated volcanic rocks were analyzed at high spatial resolution for their trace element abundances along with oxygen and hafnium isotopic compositions. Pronounced negative Eu anomalies and high incompatible trace element (e.g., Y, Hf, and U) abundances in zircon along with low Ti-in-zircon temperatures reveal that the GPC microgranite porphyry magma was more evolved than GPC granite and granodiorite. Isotopically, GPC microgranite porphyry, granite, and granodiorite zircon crystals closely overlap (δ18O = +4.76 to +9.18; εHf = +1.4 to +10.7), but a subpopulation with elevated δ18O (∼8.05) and lower εHf (∼4.4) is only present in GPC granite and granodiorite. Zircon from coeval volcanic units share this dichotomy, with a dominant population at (δ18O = +4.92 to +9.38; εHf = +3.4 to +11.3) and a generally minor population with elevated δ18O and low εHf, which is particularly prominent in dacite of Cobb Valley. Anticorrelated δ18O and εHf values indicate progressive assimilation of Franciscan Complex basement rocks, but fractional crystallization was decoupled from crustal assimilation. Together with published U-Th-Pb geochronology, these data reveal distinct degrees of crust-mantle interaction and constrain the thermochemical conditions during different stages in the evolution of a composite intrusive body that fed the GPC and contemporaneous volcanoes. A thermal model for such a body emplaced at ∼7 km depth quantitatively matches the GPC zircon age distribution when magma accumulation started at low recharge rates (0.1 km3/ka), intermittently peaked during a brief flare-up (4 km3/ka for 50 ka), and then returned to a low recharge flux (0.1 km3/ka). This model also qualitatively explains the initial presence of small-volume, highly evolved melts forming the microgranite porphyry, followed by massive emplacement of less evolved magmas forming the GPC granite-granodiorite complex. During this second stage, crustal assimilation locally intensified due to prior thermal priming of the country rock. The total injected magma volume into the upper-crustal reservoir between c. 2.1 and 1.1 Ma amounts to ∼300 km3, which is about three to four times the known volume from geothermal well penetration into the GPC. The accumulation of large volumes of silicic magma along the western North American continental margin in the wake of the northward migrating Gorda slab edge thus appears limited to a brief (c. 50 ka) pulse of high magma influx from the mantle that was pre- and post-dated by protracted low-flux magmatism. |
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| DOI: | doi:10.1016/j.chemgeo.2023.121414 |
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| URL: | Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.
Volltext: https://doi.org/10.1016/j.chemgeo.2023.121414 |
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| | Volltext: https://www.sciencedirect.com/science/article/pii/S0009254123001146 |
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| | DOI: https://doi.org/10.1016/j.chemgeo.2023.121414 |
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| Datenträger: | Online-Ressource |
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| Sprache: | eng |
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| Sach-SW: | Geothermal energy |
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| | Hafnium isotopes |
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| | Magmatism |
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| | Oxygen isotopes |
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| | Quaternary |
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| | Trace elements |
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| | Zircon |
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| K10plus-PPN: | 1843491877 |
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| Verknüpfungen: | → Zeitschrift |
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¬A¬ common magma source for plutonic and volcanic rocks of The Geysers geothermal field, California / Angeles De La Torre, Carlos A. [VerfasserIn]; 17 March 2023 (Online-Ressource)
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