Chapter 1: Origin and evolution of the zoned La Posta-type plutons, eastern Peninsular Ranges batholith, southern and Baja California

1990 ◽  
pp. 1-18 ◽  
Author(s):  
M. J. Walawender ◽  
R. G. Gastil ◽  
J. P. Clinkenbeard ◽  
W. V. McCormick ◽  
B. G. Eastman ◽  
...  
Keyword(s):  
Baja California ◽  
Origin And Evolution ◽  
Peninsular Ranges

The Peninsular Ranges Batholith: an insight into the evolution of the Cordilleran batholiths of southwestern North America

1988 ◽  
Vol 79 (2-3) ◽  
pp. 105-121 ◽  
Author(s):  
L. T. Silver ◽  
B. W. Chappell
Keyword(s):  
Baja California ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Radiometric Dating ◽  
Island Arcs ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
Basaltic Composition ◽  
Peninsular Ranges ◽  
General Aspects

ABSTRACTThe Peninsular Ranges Batholith of southern and Baja California is the largest segment of a Cretaceous magmatic arc that was once continuous from northern California to southern Baja California. In this batholith, the emplacement of igneous rocks took place during a single sequence of magmatic activity, unlike many of the other components of the Cordilleran batholiths which formed during successive separate magmatic episodes. Detailed radiometric dating has shown that it is a composite of two batholiths. A western batholith, which was more heterogeneous in composition, formed as a static magmatic arc between 140 and 105 Ma and was intrusive in part into related volcanic rocks. The eastern batholith formed as a laterally transgressing arc which moved away from those older rocks between 105 and 80 Ma, intruding metasedimentary rocks. Rocks of the batholith range from undersaturated gabbros through to felsic granites, but tonalite is the most abundant rock throughout. Perhaps better than elsewhere in the Cordillera, the batholith shows beautifully developed asymmetries in chemical and isotopic properties. The main gradients in chemical composition from W to E are found among the trace elements, with Ba, Sr, Nb and the light rare earth elements increasing by more than a factor of two, and P, Rb, Pb, Th, Zn and Ga showing smaller increases. Mg and the transition metals decrease strongly towards the E, with Sc, V and Cu falling to less than half of their value in the most westerly rocks. Oxygen becomes very systematically more enriched in18O from W to E and the Sr, Nd and Pb isotopic systems change progressively from mantle values in the W to a more evolved character on the eastern side of the batholith. In detail the petrogenesis of the Peninsular Ranges Batholith is not completely understood, but many general aspects of the origin are clear. The exposed rocks, particularly in the western batholith, closely resemble those of present day island arcs, although the most typical and average tonalitic composition is distinctly more felsic than the mean quartz diorite or mafic andesite composition of arcs. Chemical and isotopic properties of the western part of the batholith indicate that it formed as the root of a primitive island arc on oceanic lithosphere at a convergent plate margin. Further E, the plutonic rocks appear to have been derived by partial melting from deeper sources of broadly basaltic composition at subcrustal levels. The compositional systematics of the batholith do not reflect a simple mixing of various end-members but are a reflection of the differing character of the source regions laterally and vertically away from the pre-Cretaceous continental margin.

An earthquake-explosion reversed refraction line in the Peninsular Ranges of southern California and Baja California Norte

1982 ◽  
Vol 72 (4) ◽  
pp. 1195-1206
Author(s):  
F. Alejandro Nava ◽  
James N. Brune
Keyword(s):  
Sierra Nevada ◽  
High Velocity ◽  
Southern California ◽  
Baja California ◽  
Crustal Thickness ◽  
Arrival Times ◽  
Narrow Zone ◽  
Peninsular Ranges ◽  
Thick Crust

abstract An approximate reversed refraction profile has been obtained for the center of the Peninsular Ranges of southern California and Baja California Norte using arrival times from Corona blasts to obtain the NW-SE profile, and arrival times from the well-located Pino Solo earthquake of 17 July 1975 to obtain the reversing SE-NW profile. The results indicate a relatively high-velocity crust, with P velocities of 6.57 to 6.95 km/sec, similar to the high velocities found by Hadley and Kanamori (1979). A crustal thickness of about 40 km was found for the axis of the Peninsular Ranges, significantly greater than was found by Hadley and Kanamori (1979) for the average crustal thickness of the northern part of the province. This suggests that the thick crust may be confined to a relatively narrow zone along the axis of the province. The crustal thickness found here is approximately 10 km less than found for the deeper crust of the Sierra Nevada (Bateman and Eaton, 1967; Pakiser and Brune, 1980).

Structure, emplacement and lateral expansion of the San José tonalite pluton, Peninsular Ranges batholith, Baja California, México

2003 ◽  
Vol 25 (11) ◽  
pp. 1933-1957 ◽  
Author(s):  
S.E Johnson ◽  
J.M Fletcher ◽  
C.M Fanning ◽  
R.H Vernon ◽  
S.R Paterson ◽  
...  
Keyword(s):  
Baja California ◽  
San Jose ◽  
Lateral Expansion ◽  
Peninsular Ranges
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