New geologic mapping and SHRIMP U-Pb zircon data in the Peninsular Ranges batholith, Baja California, Mexico: Evidence for a suture?

Johnson, Scott E.; Tate, Marcus C.; Fanning, Christopher

doi:10.1130/0091-7613(1999)027<0743:ngmasu>2.3.co;2

Cited by 92 publications

(97 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The plutonic bodies intrude lower greenschist grade metamorphic rocks of volcanic arc assemblage and are variably overprinted by subsolidus ductile deformation (Gastil, 1975;Todd et al, 1988). The eastern zone is dominated by early Mesozoic to Late Cretaceous plutons of tonalite, granodiorite, and granite composition (Gastil, 1975;Silver and Chappel, 1988;Johnson et al, 1999). These plutons intrude Paleozoic sedimentary rocks, which have been metamorphosed to upper greenschist and amphibolite facies conditions (Gastil and Miller, 1993).…”

Section: Geology Of the Baja California Microplatementioning

confidence: 99%

“…The batholith is subdivided into a western and eastern plutonic zone, which reflect intrusions into the crust of oceanic and continental affinity, respectively (Gastil, 1975;Silver and Chappel, 1988). The western zone of the batholith consists of Middle Jurassic to middle Cretaceous plutons ranging in composition from gabbro to tonalite (Silver and Chappel, 1988;Tate and Johnson, 2000;Johnson et al, 1999). The plutonic bodies intrude lower greenschist grade metamorphic rocks of volcanic arc assemblage and are variably overprinted by subsolidus ductile deformation (Gastil, 1975;Todd et al, 1988).…”

Section: Geology Of the Baja California Microplatementioning

confidence: 99%

See 1 more Smart Citation

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

et al. 2017

View full text Add to dashboard Cite

Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.

show abstract

Section: Geology Of the Baja California Microplatementioning

confidence: 99%

Section: Geology Of the Baja California Microplatementioning

confidence: 99%

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Cretaceous intrusions in the western Peninsular Ranges Batholith (PRB) were emplaced about ca.140 Ma. 16,17 Compositions range from gabbro to rare granite that includes low K quartz gabbro to quartz diorite. The north-western PRB includes gneiss-granite in a belt that extends at 150 km northbound, beyond the international USA border.…”

Section: Geological Settingmentioning

confidence: 99%

“…16 The eastern PRB varies in composition from gabbro to rare granite but are dominated by tonalite-trondhjemite-granodiorite or biotite tonalite. 15,[17][18][19][20][21] These rocks are lower in dark minerals and potash feldspar (low in K 2 0, FeO, and MgO, and high in Si0 2 and Al 2 0 3 ) than the rocks of the western part of the batholith. 22 Marine Palaeocene and early Eocene strata occur in many places along and south from the Western Cape territory of Baja California.…”

Section: Geological Settingmentioning

confidence: 99%

Investigating regional groundwater flow systems in baja california central desert region

Ouysse¹,

Wehncke²,

Rivera³

2018

IJH

View full text Add to dashboard Cite

In Northern Baja California, environmental conservation may not be fully accomplished in the absence of a clear understanding of key factors controlling and protecting biodiversity. Groundwater is an environmental agent triggering the presence of a wide range of arid ecosystems; therefore, any sustainable development in the region has to maintain a balance between environmental, social and economical benefits. The present study has placed a great emphasis on the understanding and distribution of groundwater flow systems, and their environmental interactions in the protected area of the Valle de Los Círios, using physical-chemical and isotope methods. Results show the presence of three groundwater groups portraying contrasting flow systems conditions. Analyzed samples have been classified as fresh-brackish, and thermal alkaline groundwater as suggested by pH, temperature and TDS. The Br/Cl ratio in most samples was close to the ocean molar value (1.5x10 -3 ) indicating the importance of marine aerosol fraction in the recharged waters; however, Mg/Cl,Na/Cl,Ca/Cl,SO 4 / Cl and Cl/HCO 3 +Cl ratios were significantly different to those of seawater mixing conditions. Dominant ions (Na,Ca and Cl), chemical age proxies (Li), and δ 18 O suggest waters with long residence time, with the possibility of been recharge during the late glacial period. Thermal ground water shows low minor and trace element content and exhibits the dominance of Na-plagioclase hydrolysis; their low levels of Sr and Ba suggest negligible contact with calcareous rocks and their estimated temperature at depth (80to100°C) and TDS suggest groundwater has travelled through fractured media. This introduction study suggests that desertic species in Valle de Los Cirios are highly sustained by groundwater of local and intermediate flows.

show abstract

“…An I-S line, which largely reflects Jurassic plutonism, and an oxygen isotope gap, also closely approximate the other lines (Taylor and Silver 1978;Todd and Shaw 1985). In the west, Cretaceous plutons range in age from 128-100 Ma and have no systematic age distribution; whereas to the east large nested tonalite-granodiorite-granite complexes, called the La Posta suite, range in age from 99-92 Ma and young progressively eastward (Silver and Chappell 1988;Walawender et al 1990;Johnson et al 1999b;Kimbrough et al 2001;Schmidt et al 2014). This distribution of ages led Silver (Silver et al 1979;Silver and Chappell 1988) to suggest that a magmatic arc remained fixed in the west until 105 Ma and then migrated eastward.…”

Section: Geological Settingmentioning

confidence: 99%

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

Hildebrand

Whalen

2014

View full text Add to dashboard Cite

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.

show abstract

New geologic mapping and SHRIMP U-Pb zircon data in the Peninsular Ranges batholith, Baja California, Mexico: Evidence for a suture?

Cited by 92 publications

References 14 publications

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

Investigating regional groundwater flow systems in baja california central desert region

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

Contact Info

Product

Resources

About