S-type granitoids and an I-S line in the Peninsular Ranges batholith, southern California

Todd, Victoria R.; Shaw, S. E.

doi:10.1130/0091-7613(1985)13<231:sgaail>2.0.co;2

Cited by 48 publications

(29 citation statements)

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“…On the basis of these discontinuities, Todd and Shaw (1985) suggested they are indicative of a fundamental change in the Mesozoic crust, possibly a suspect terrane boundary formed by the accretion of a western volcanic arc and the continental margin to the east. Schmidt and Paterson (2002) describe the boundary as an example of crustal transition between juxtaposed oceanic and continental fl oored arcs, with Jurassic-Cretaceous deforma- Figure 1.…”

Section: Geological Settingmentioning

confidence: 98%

Jurassic peraluminous gneissic granites in the axial zone of the Peninsular Ranges, southern California

Shaw¹,

Todd²,

Grove

2003

Tectonic Evolution of Northwestern Mexico and the Southwestern USA

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The Peninsular Ranges batholith of southern California and Baja California, México, is well recognized as a prime example of an I-type Cretaceous batholith. Often overlooked, however, is a volumetrically signifi cant amount of pre-Cretaceous gneissic granite in the axial zone of the batholith. New U-Pb zircon age data confi rm that the metaluminous and peraluminous plutonic bodies were emplaced during the middle Jurassic. Also reported in this paper is a Jurassic U-Pb age for a metaluminous (I-type) tonalite-quartz diorite pluton that is spatially related to the peraluminous suites. This result suggests that other unrecognized Jurassic I-type plutons may also be present in the batholith.Within San Diego County, Todd and Shaw (1985) recognized and mapped two suites of strongly deformed gneissic granites and migmatites. One is peraluminous (Harper Creek suite) while the other is transitional between metaluminous and peraluminous (Cuyamaca Reservoir suite). These rocks bear a striking resemblance to deformed and, in places, migmatitic, peraluminous (S-type) examples from the Lachlan fold belt and New England batholith of eastern Australia. The gneissic granite suites are known to extend north along the axial zone of the Peninsular Ranges batholith and cover an area at least 45 km wide by 150 km long. To the south, rocks of similar type are known to extend into Baja California, México, for at least 300 km. Chemical and isotopic studies of these Jurassic suites confi rm that they meet the criteria necessary to defi ne them as S-type and transitional I-to S-type, respectively. However, unlike the majority of Lachlan fold belt S-type granites that are high level and often associated with their volcanic equivalents, the Peninsular Ranges batholith suites were emplaced at much deeper levels, possibly as much as 11-16 km. The Harper Creek suite, of S-type gneissic granodiorite-tonalite plutons and associated Stephenson Peak migmatitic schist and gneiss facies, is strongly peraluminous and contains biotite, cordierite, sillimanite, abundant graphite, and ilmenite. It has elevated δ 18 O up to +20 per mil, initial 87 Sr/ 86 Sr ratios (Sr i ) to 0.713, a high aluminum saturation index, and Na 2 O/K 2 O ratios that overlap those of the Lachlan fold belt S-type granites. The Cuyamaca Reservoir suite contains gneissic granodioritetonalite plutons, transitional between metaluminous and moderately peraluminous (Ito S-type), containing reduced biotite, subaluminous amphibole, orthopyroxene, titanite Shaw, S.E.,

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Section: Geological Settingmentioning

confidence: 98%

Jurassic peraluminous gneissic granites in the axial zone of the Peninsular Ranges, southern California

Shaw¹,

Todd²,

Grove

2003

Tectonic Evolution of Northwestern Mexico and the Southwestern USA

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“…1989) as indicated by the controversy over whether the two-mica granites from the Peninsular Range Batholith are S-type granitoids or not (e.g. Todd and Shaw 1985;White et al 1986). …”

Section: Origin and Tectonic Settingmentioning

confidence: 99%

Granitoids: Main petrogenetic classifications in relation to origin and tectonic setting

Barbarin

1990

Geological Journal

210

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Comparison of the twenty most frequently used petrogenetic classifications of granitoids is summarized using petrography, nature and abundance of enclaves, mineralogy, major and trace element, and isotope geochemistry. This comparison indicates considerable agreement between most authors concerning the main divisions. Differences result either from different genetic models or from the weighting of the criteria used, such as nature of the source, relative proportions of crustal and mantle contributions, magmatic processes, and types of emplacement. In the classification proposed here, three main groups of granitoids correspond respectively to a crustal, a mantle, or a mixed (crustal and mantle) origin of the magmas. Each of these main groups is subdivided into two or three types. Distinct petrographic, mineralogical, and chemical characteristics result from differences in the origin and tectonic setting of the granitoid magmas. Consequently, granitoids with well-defined petrographic, mineralogical, chemical features and ages may provide information on the changes of tectonic settings with space, time, or both, i.e. they may be used as geotectonic tracers.

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“…I-, S-, and transitional I-S-type gneissic granites of Mid- have been recognized in San Diego, southern California (Todd and Shaw, 1985;Shaw et al, 2003). The zircons have an inherited Precambrian component (Gastil and Girty, 1993).…”

Section: Evidence Of Jurassic Magmatismmentioning

confidence: 98%

Re–Os and U–Pb geochronology of the El Arco porphyry copper deposit, Baja California Mexico: Implications for the Jurassic tectonic setting

Valencia

Barra

Weber

et al. 2006

Journal of South American Earth Sciences

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S-type granitoids and an I-S line in the Peninsular Ranges batholith, southern California

Cited by 48 publications

References 0 publications

Jurassic peraluminous gneissic granites in the axial zone of the Peninsular Ranges, southern California

Jurassic peraluminous gneissic granites in the axial zone of the Peninsular Ranges, southern California

Granitoids: Main petrogenetic classifications in relation to origin and tectonic setting

Re–Os and U–Pb geochronology of the El Arco porphyry copper deposit, Baja California Mexico: Implications for the Jurassic tectonic setting

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