Strontium and neodymium isotope geochemistry of igneous rocks from the North East Pacific and Gulf of California

Verma, Surendra P.

doi:10.1016/s0009-2541(83)80028-x

Cited by 6 publications

(2 citation statements)

References 28 publications

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“…Under this hypothesis, fractional crystallization that was potentially combined with crustal contamination or assimilation is responsible for evolution of the alkaline magmas, which are highly differentiated from the transitional basalts or moderately alkaline magma. Similar processes have been proposed by various authors (e.g., Cameron & Cameron, 1986a;Ferriz & Mahood, 1987;Halliday, Fallick, Hutchinson, & Hildreth, 1984;Halliday, Mahood, Hildreth, Holden, & Stephens, 1987;Halliday, Shepherd, Dickin, MacLaren, & Darbyshire, 1986;Hildreth, 1987;Moll-Stalcup, 1987;Novak & Mahood, 1986;Verma, 1983aVerma, , 1983bVerma, , 1984 to explain the genesis of high-silica rhyolites in many environments, such as the Volcanic Center Sierra La Primavera (Pleistocene-Mexico, Mahood & Halliday, 1988). Recent studies (e.g., Bachmann & Bergantz, 2004;Hildreth, 2004;Lipman, 2007) propose that high-silica rhyolites originated from the separation of liquids derived from rhyolitic crystal mush linked to large granodioritic or granitic plutons.…”

Section: Discussionsupporting

confidence: 78%

High‐silica Ediacaran volcanism in the Dom Feliciano Belt, southernmost Brazil

et al. 2018

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The Cerro Chato region is located in southernmost Brazil and is characterized by associations of acid volcanic and subvolcanic rocks. The region is affected by NW and NE‐ trending faults and is grouped into 2 geomorphologically distinct features: Cerro Chato and Cerro Partido. Cerro Chato is represented by ignimbrites that occur in 2 main facies: lithic‐rich ignimbrites and crystal‐rich ignimbrites. They are poorly sorted and consist of lapilli‐sized pyroclasts in a tuffaceous matrix with eutaxitic texture. Hemi‐crystalline rhyolitic flows represent effusive events, with porphyritic texture, flow structures, and spherulites. Cerro Partido is characterized by a subvolcanic rhyolitic body, with porphyritic texture, elongated in the NE–SW direction. Through geochemical data, the lithologies were characterized as high‐silica type rhyolites, correlated to the alkaline series, close to the subalkaline series limit; display metaluminous to peraluminous character and high contents of alkalis, FeOt/FeOt + MgO and agpaitic index. The Cerro Partido rhyolites were classified as high‐Ti with higher CaO, P2O5, FeOt, MgO, and K2O contents than the Cerro Chato low‐Ti rhyolites. The REE pattern is slightly enriched in LREE in relation to the HREE and has a strong negative Eu anomaly. U–Pb zircon dating indicates an age of 561 ± 2 Ma for Cerro Partido, suggesting contemporaneity with the granitoids of Dom Feliciano Suite. Additionally, Cerro Chato rhyolites indicate an age of 630.4 ± 2.8 Ma. These ages are in agreement with those obtained in the syn‐sedimentary volcanism at the base of the Maricá Formation, Camaquã Basin.

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Section: Discussionsupporting

confidence: 78%

High‐silica Ediacaran volcanism in the Dom Feliciano Belt, southernmost Brazil

et al. 2018

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“… Schilling et al [1982]identify a well‐defined, long‐wavelength, symmetrical pattern of increasing plume contribution to axial lavas along the GSC as it nears the Galápagos Archipelago. This pattern is manifest in enriched radiogenic isotope ratios (Pb, Sr, Hf, Nd) and incompatible element ratios (e.g., K/Ti; La/Yb) [ Verma and Schilling , 1982; Verma , 1983; Detrick et al , 2002; Schilling et al , 2003; Cushman et al , 2004; Christie et al , 2005; Kokfelt et al , 2005] and is continuous in axial lavas across the 90.5°W Galápagos Transform Fault (GTF) [ Schilling et al , 1982, 2003; Christie et al , 2005].…”

Section: Introductionmentioning

confidence: 99%

Multiple expressions of plume‐ridge interaction in the Galápagos: Volcanic lineaments and ridge jumps

Mittelstaedt¹,

Soule²,

Harpp³

et al. 2012

Geochem Geophys Geosyst

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[1] Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May-June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that $94% of the excess volcanism in our Copyright 2012 by the American Geophysical Union 1 of 31 survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a $60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field.We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since $5 Ma.

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