Batholith and associated rocks of Corona, Elsinore, and San Luis Rey quadrangles, Southern California.

Format:

Book

Author/Creator:

Larsen, Esper S. (Esper Signius), 1879-1961.

Contributor:

Geological Society of America.

Series:

Memoir (Geological Society of America) ; 29.

Geological Society of America. Memoir ; 29

Language:

English

Subjects (All):

Petrology--California, Southern.

Petrology.

Igneous rocks.

Batholiths.

Southern California.

Physical Description:

1 online resource (x, 182 pages) : illustrations, maps (l color in pocket).

Place of Publication:

[New York] : Geological Society of America, 1948.

System Details:

Master and use copy. Digital master created according to Benchmark for Faithful Digital Reproductions of Monographs and Serials, Version 1. Digital Library Federation, December 2002. http://purl.oclc.org/DLF/benchrepro0212

text file

Summary:

The batholith of southern and Lower California is exposed continuously from near Riverside, California, southward for a distance of about 350 miles. In central Lower California it is covered in part by younger rocks, but discontinuous bodies extend to the southern end of Lower California. The batholith is probably over 1000 miles long. Its width is about 60 miles. A strip about 70 miles wide across the northern part of the batholith has been studied ; the western half was mapped in detail, and the eastern half was covered in rapid reconnaissance. In the area studied the batholith intrudes Triassic sediments and Jurassic volcanic rocks along its western border, and Paleozoic sediments along its eastern border. Screens and roof pendants are common within the batholith. The Triassic rocks are mildly metamorphosed in the western part of the area but become progressively more coarsely crystalline toward the east. The Palezoic rocks are rather coarsely crystalline. The metamorphism in large part preceded the intrusion of the batholith, and only locally was there appreciable contact metamorphism. The batholith and older rocks are overlain by Upper Cretaceous and younger sediments. Small bodies of andesite and basalt of Quaternary age are present in the area. The batholith was intruded in early Upper Cretaceous time. The batholith in the area studied was emplaced by more than 20 separate injections. Most of the resulting rock types are found in only one or a few small bodies which are confined to a small area. In the area studied in detail (pi. 1) five types are present in many large, widely sepai-ated bodies, making up about 88 percent of the area underlain by the batholith. In the eastern half of the batholith three more widespread types are present. In the western half of the body the rocks range from gabbro to granite, but in the eastern half several tonalites constitute nearly the whole of the mass. The gabbro is composed of many related rocks. Some have hornblende, some pyroxene ; in some the plagioclase is anorthite, in others it is as sodic as andesine-labradorite. Some of the tonalites contain abundant inclusions that have been almost completely reworked by the magma and have been softened and stretched into thin discs. These inclusions are well oriented, and near the contacts with older rocks they parallel the contacts ; elsewhere they strike about N. 30° W. and dip steeply to the east. One tonalite, whose feldspar is andesine, has scattered crystals with cores of bytownite, and has well-crystallized hornblende with cores of pale uralitic hornblende and remnants of augite. Hornblende and biotite are the predominant mafic minerals of the tonalites and granodiorites. The general strike of the structures of the area have been about N. 30° "W. from Paleozoic to the present time. The Paleozoic and Triassic sediments, the orientation of the inclusions and other structures of the batholith, the elongation of the batholith and the mountain ranges, and the strike of the major faults are in about the same direction. In the batholith and the older sediments the dips are steep to the east. The batholith must have been emplaced by stoping and not by forceful injection. The different rocks of the batholith were formed from the intermediate gabbro by crystal differentiation and assimilation in depth. In early Upper Cretaceous time diastrophism folded the older rocks and formed, in depth, a strip of gabbroic magma about 1000 miles long. A small amount of this magma was intruded nearly to the surface. The deep magma differentiated quietly until its upper part attained the composition of a tonalite. Earth movements then occurred at least five times in rapid succession and caused the injection of the different tonalites. Some of these carry abundant inclusions, indicating a widespread shattering of the wall rock shortly before final emplacement. From time to time local movements caused the injections of the different granodiorites. When the deep-seated magma reached the composition of a light-colored granodiorite, widespread diastrophism moved the main granodiorite upward. Further local moremeut caused the emplacement of the many local granodiorites and granites.

Contents:

Abstract

Introduction

Physiography

Pre-batholith sedimentary rocks

Santiago Peak volcanics

Metamorphism

Temescal Wash quartz latite porphyry

Dark granodiorite porphyry east of Corona

Serpentine

San Marcos gabbro

Green Valley tonalite

Lakeview Mountain tonalite

Bonsall tonalite

Granodiorite west of Lakeview

Streaking and inclusions

Chemical composition of the Bonsall and Lakeview Mountain tonalites and related rocks

Granitic rocks of the San Jacinto and Ramona quadrangles

Tonalite similar to the Bonsall tonalite in the southern Sierra Nevada

Domenigoni Valley granodiorite

Estelle tonalite

La Sierra tonalite

Miscellaneous tonalites

Woodson Mountain granodiorite

Lake Wolford leucogranodiorite

Escondido Creek Leucogranodiorite

Mt. Hole granodiorite

Granodiorirty porphyry

Miscellaneous granodiorites

Roblar leucogranite

Micropegmatite granite

Two leucogranites of Rubidoux Mountain

Aplite, ap itic rocks and pegmatite

Mafic dikes

Quartz latite porphyry

Tourmaline and epidote rock

Tertiary volcanics rocks

Quaternary basalt

Weathering

Structure

Natural resources

General character of the batholith

References cites

Index.

Notes:

Electronic reproduction. [S.l.] : HathiTrust Digital Library, 2011.

Print version record.

Other Format:

Print version: Larsen, Esper S. (Esper Signius), 1879-1961. Batholith and associated rocks of Corona, Elsinore, and San Luis Rey quadrangles, Southern California.

OCLC:

765373290

Access Restriction:

Restricted for use by site license.