Cretaceous plutons of the Peninsular Ranges Batholith, San Diego and westernmost Imperial Counties, California: Intrusion across a Late Jurassic continental margin

Todd, Victoria R.; Shaw, S. E.; Hammarstrom, Jane M.

doi:10.1130/0-8137-2374-4.185

Cited by 26 publications

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“…The Peninsular Ranges is generally divided into eastern and western arcs (Johnson et al 1999) that range in age from 140 to 94 Ma, with the majority of plutons falling between 120 and 95 Ma (George and Dokka 1994;Johnson et al 1999;Kistler et al 2003;Ortega-Rivera 2003;Wetmore et al 2003). The eastern arc is continental in character, with 99-92 Ma tonalitic and granodioritic plutons that have 87 Sr/ 86 Sr values close to 0.708 (DePaolo 1981;Kimbrough et al 2001;Kistler et al 2003), while the western arc includes 140-105 Ma gabbroic to monzogranitic plutons with 87 Sr/ 86 Sr ≤ 0.704 and Nd ≥ +3.7 and a more significant volcanic component than the eastern arc (DePaolo 1981;Johnson et al 1999;Kimbrough et al 2001;Todd et al 2003). The Albian Alisitos Formation is a clastic sedimentary sequence in the western arc of the Peninsular Ranges that contains abundant volcanic lithic grains (Wetmore et al 2003), unlike the coeval lithic-poor strata of the Harts Pass Formation in the Methow basin.…”

Section: Tectonic Implications Of Methow Provenancementioning

confidence: 99%

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

2014

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Abstract:The Jurassic-Cretaceous Methow basin of northern Washington State and southern British Columbia forms an overlap sequence linking several small tectonostratigraphic terranes. Sandstone petrography, sandstone and mudrock geochemistry, and detrital zircon U-Pb age and Hf analysis of mid-Cretaceous, east-derived Methow strata together document a remarkably uniform provenance signature that suggests proximal, abundant, and unchanging sediment sources throughout deposition. The eastern belt of the Coast Mountains batholith, intruded into Stikine and related inboard terranes of the Intermontane superterrane, along with Jurassic and Cretaceous plutons of the westernmost Okanogan Range, provide the best match to the provenance signature of east-derived sediment in the Methow basin during the mid-Cretaceous. Furthermore, the Cretaceous and Jurassic plutons of the eastern Coast Mountains batholith and western Okanogan Range were rapidly uplifted to provide the substantial thickness of sediment in the Methow basin, and they must have acted as a topographic barrier that effectively prevented sediment derived from the continental interior from reaching the basin. This uplift of a proximal eastern source occurred during regional late Early Cretaceous sinistral transpression and resulted in subsidence of the Methow trough and rapid deposition of east-derived strata in the Methow basin. Because Methow sediment sources apparently did not include the North American interior, the extent of post-depositional large-scale translation relative to the North American craton of the Methow basin with its proximal, eastern sources cannot be unequivocally determined.Résumé : Le bassin de Methow (Jurassique-Crétacé) du nord de l'État de Washington et du sud de la Colombie-Britannique forme une séquence de chevauchement reliant plusieurs petits terranes tectonostratigraphiques. La pétrographie des grès, la géochimie des grès et des pélites ainsi que les âges déterminés par U-Pb sur des zircons détritiques et des analyses Hf des strates de Methow provenant de l'est (Crétacé moyen) documentent ensemble une signature de provenance remarquablement uniforme, suggérant des sédiments de sources proximales, abondantes et inchangées durant toute la déposition. La ceinture est du batholite de la Chaîne côtière, introduite dans le terrane de Stikine et d'autres terranes intérieurs reliés du superterrane intermontagneux, et les plutons datant du Jurassique et du Crétacé de la partie la plus à l'ouest du chaînon Okanogan, fournissent la meilleure concordance pour une signature de provenance de sédiments de l'est vers le bassin de Methow au Crétacé moyen. De plus, les plutons datant du Crétacé et du Jurassique du batholite de l'est de la chaîne Côtière et de l'ouest du chaînon Okanagan ont été soulevés rapidement, fournissant l'importante épaisseur de sédiments dans le bassin de Methow, et ils ont dû agir de barrière topographique qui a effectivement empêché les sédiments provenant de l'intérieur du continent d'atteindre le bassin. Ce soulèvement ...

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Section: Tectonic Implications Of Methow Provenancementioning

confidence: 99%

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

2014

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“…In the Southern California segment of the batholith the depth of emplacement of all plutons, based on Al-in-hornblende barometry, increases from about 2 kbar or less in the west, to more than 5 kbar in the eastern zone (Ague and Brimhall 1988;Todd et al 2003). In the Sierra de San Pedro Mártir, farther south (Fig.…”

Section: Exhumationmentioning

confidence: 97%

“…Farther south, in the Sierra Calumague, the eastern boundary is thought to be represented by ductile faults, which commonly, but not everywhere, dip steeply eastward, and are probably normal faults as they place lower grade rocks atop higher grade rocks (Griffith and Hobbs 1993). Within the US segment of the batholith, the contact is generally inferred to coincide with the geophysical, isotopic, and geochemical breaks, yet similar plutonic rocks appear on both sides of it, leading some workers, such as Todd et al (2003) to argue that Cretaceous arc magmatism simply migrated eastward over a pre-existing Late Jurassic-Early Cretaceous crustal boundary. They did not explain why plutons and wall rocks older than about 100 Ma are deformed and metamorphosed, whereas younger plutons are not.…”

Section: Geological Settingmentioning

confidence: 99%

“…6) represent an intense magmatic pulse ranging in age from 99-85 Ma (Silver and Chappell 1988;Walawender et al 1990;Kimbrough et al 2001;Premo et al 2014b). The plutons were emplaced at depths of 5-23 km into upper greenschist, but mainly amphibolite, grade wall rocks that are in many places migmatitic Ague and Brimhall 1988;Todd et al 1988Todd et al , 2003Grove 1993;Rothstein 1997;Rothstein and Manning 2003;Gastil et al 2014). The plutons were intruded during a period of exhumation when rocks at depths of 15-23 km were brought rapidly to the surface by detachment faulting and collapse (Krummenacher et al 1975;George and Dokka 1994;Ortega-Rivera et al 1997, Ortega-Rivera 2003Grove et al 2003;Miggins et al 2014).…”

Section: Exhumationmentioning

confidence: 99%

“…Fifteen years later, Todd et al (2003) ; the boundary between ferroan and magnesian plutons has been modified as suggested by Frost and Frost (2008); (c) Na 2 O+K 2 O-CaO (or MALI) vs. SiO 2 granitic rock classification diagrams of Frost et al (2001). Ranges for alkali-calcic, calc-alkalic, and calcic rock series, based on the alkali-lime classification of Peacock (1931).…”

Section: Previous Modelsmentioning

confidence: 99%

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Arc and Slab-Failure Magmatism in Cordilleran Batholiths II – The Cretaceous Peninsular Ranges Batholith of Southern and Baja California

Hildebrand

Whalen

2014

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Ever since the late 1960s when Warren Hamilton proposed that the great Cordilleran batholiths of the western Americas are the roots of volcanic arcs like the Andes and were generated by longstanding eastward subduction, most geologists have followed suit, despite the evergrowing recognition that many Cordilleran batholiths are complex, composite bodies that developed with intervals of intense shortening and exhumation between and during periods of magmatism. The Peninsular Ranges batholith of Southern and Baja California provides a superb place to unravel the complexities because there is a lot of data and because it is longitudinally composed of two parts: an older western portion of weakly to moderately deformed, low-grade volcanic and epizonal plutonic rocks ranging in age from ~128–100 Ma; and a more easterly sector of deformed amphibolite grade rocks cut by compositionally zoned, mesozonal plutonic complexes of the La Posta suite, emplaced from 99–86 Ma. While plutons of the La Posta suite are generally considered to be the product of continued eastward subduction, they are enigmatic, because they and their wall rocks were rapidly exhumed from as deep as 23 km and eroded during, and just after, their emplacement, unlike plutons in magmatic arcs, which are generally emplaced in zones of subsidence. Here we resolve the enigma with a model where westward-dipping subduction led to arc magmatism of the western sector, the Santiago Peak–Alisitos composite arc, during the period ~128–100 Ma. Arc magmatism shut down when the arc collided with a west-facing Early Cretaceous passive margin at about 100 Ma. During the collision the buoyancy contrast between the continental crust of the eastern block and its attached oceanic lithosphere led to failure of the subducting slab. The break-off allowed subjacent asthenosphere to upwell, adiabatically melt, and rise into the upper plate to create the large zoned tonalite–granodiorite–granite complexes of the La Posta suite. While compositionally similar to arc plutons in many respects, the examples from the Southern California and Baja segments of the batholith have geochemistry that indicates they were derived from partial melting of asthenosphere at deeper levels in the mantle than typical arc magmas, and within the garnet stability field. This is consistent with asthenosphere upwelling through the torn lower-plate slab. We identify kindred rocks with similar geological relations in other Cordilleran batholiths of the Americas, such as the Sierra Nevada, which lead us to suggest that slab failure magmatism is common, both spatially and temporally.SOMMAIREDepuis la fin des années 1960, Warren Hamilton a proposé que les grands batholites de la Cordillère de l'ouest des Amériques sont les racines d’arcs volcaniques andéens issus de la subduction vers l'est de longue durée, et depuis la plupart des géologues ont emboîté le pas, bien qu’un nombre croissant d’indications montrent que de nombreux batholites de la Cordillère sont des entités composites complexes qui se sont développés lors d’intervalles intenses de contraction et d’exhumation, durant et entre les périodes de magmatisme. Le batholite Peninsular Ranges du Sud de la Californie et de Baja California est un excellent endroit permettant de démêler les choses parce qu'il y a beaucoup de données et parce qu'il est composé longitudinalement de deux parties: une partie occidentale plus ancienne, faiblement à modérément déformée, de roches volcaniques de faible métamorphisme et de roches plutoniques épizonales âgées d’environ 128 Ma à 100 Ma; et, d’un segment plus à l'est de roches amphiboliques déformées recoupées par des roches de composition zonée des complexes mésozonaux plutoniques de la suite de la Posta, mises en place entre 99 Ma et 86 Ma. Bien que les plutons de la suite La Posta sont généralement considérés comme le produit d’une subduction soutenue vers l’est, ils posent problème, parce qu'avec leurs roches encaissantes, ils ont été rapidement exhumés de profondeurs aussi grandes que 23 km, et érodées durant et juste après leur mise en place, contrairement aux plutons des arcs magmatiques, qui sont généralement mis en place dans les zones de subsidence. Dans le présent article, nous proposons une solution à ce problème, avec un modèle de subduction vers l'ouest qui conduit à un magmatisme d'arc du secteur ouest, l'arc composite de Santiago Peak-Alisitos, durant la période d’environ 128 Ma à 100 Ma. Le magmatisme d’arc s’est arrêté lorsque l'arc est entré en collision avec une marge passive à pendage ouest du début du Crétacé, il y a environ 100 Ma. Lors de la collision, le contraste de flottabilité entre la croûte continentale du bloc de est et la lithosphère océanique qui y est rattachée a conduit à l'avortement de la plaque plongeante. La cassure a entrainé la remontée de l’asthénosphère sous-jacente, sa fusion adiabatique, et sa remontée dans la plaque supérieure pour former les grands complexes zonés de tonalite-granodiorite-granite de La Posta. Bien que de composition similaire aux plutons d'arc à bien des égards, les exemples des segments de batholites de Californie du Sud et de Baja ont une géochimie qui indique qu'ils proviennent de la fusion partielle de l’asthénosphère à des niveaux plus profonds dans le manteau que les magmas d'arc typiques, à l’intérieur du domaine de stabilité du grenat. Ce qui correspond à une remontée d’asthénosphère à travers une dalle de plaque inférieure cassée. Nous connaissons des roches semblables avec les relations géologiques similaires dans d'autres batholites de la Cordillère des Amériques, tel celles de la Sierra Nevada, ce qui nous amène à penser que le magmatisme de cassure de plaque est commun, tant spatialement et temporellement.

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San Andreas Fault dip, Peninsular Ranges mafic lower crust and partial melt in the Salton Trough, Southern California, from ambient‐noise tomography

Barak

Klemperer

Lawrence

2015

Geochem Geophys Geosyst

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We use ambient-noise tomography to improve CVM-H11.9, a community velocity model of southern California. Our new 3-D shear-velocity model with 0:05 x 0:05 lateral and 1 km vertical blocks reveals new structure beneath the San Andreas Fault (SAF), Peninsular Ranges batholith (PRB), southern Sierra Nevada batholith (SNB), and the Salton Trough (ST). We use 4 years of data recorded on 849 broadband stations, vastly more than previous studies and including our own broadband Salton Seismic Imaging Project, a 40 station transect across the ST, as well as other campaign stations in both Mexico and the United States. Mean lower crust and upper mantle wave speeds (3.6 km/s at 20 km, 4.2 km/s at 40 km) are low by global standards. Across the SAF, southeast of San Gorgonio Pass, we observe vertical to steeply dipping lateral velocity contrasts that extend beneath the Moho. Beneath the western PRB and westernmost southern SNB, we observe relatively high shear velocities (!3.8 km/s) in the lower crust that we interpret as the mafic roots of the overlying arc. Relatively high-velocity upper mantle (up to $4.5 km/s) may be part of the intact arc, or possibly a remnant of the Farallon plate. Beneath the ST, we observe zones of low shearvelocity in the lower crust and upper mantle which permit up to $4.5% melt in the lower crust and up to $6% melt in the upper mantle, depending on the assumed composition and pore geometry. Our results preclude the existence of older continental crust beneath the ST and support the creation of new crust beneath the ST.

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Cretaceous plutons of the Peninsular Ranges Batholith, San Diego and westernmost Imperial Counties, California: Intrusion across a Late Jurassic continental margin

Cited by 26 publications

References 0 publications

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

East-derived strata in the Methow basin record rapid mid-Cretaceous uplift of the southern Coast Mountains batholith

Arc and Slab-Failure Magmatism in Cordilleran Batholiths II – The Cretaceous Peninsular Ranges Batholith of Southern and Baja California

San Andreas Fault dip, Peninsular Ranges mafic lower crust and partial melt in the Salton Trough, Southern California, from ambient‐noise tomography

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