The Petrology and Geochemistry of Gabbros from the Peninsular Ranges Batholith, California, and a Model for the Origin PDF Download

Author: Richard Kiichi Nishimori
Publisher:
ISBN:
Category : Gabbro
Languages : en
Pages : 586

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Author: Richard Kiichi Nishimori
Publisher:
ISBN:
Category :
Languages : en
Pages : 468

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Author: Clayton R. Gautier
Publisher:
ISBN:
Category : Ecological surveys
Languages : en
Pages : 88

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Author: Scripps Institution of Oceanography
Publisher:
ISBN:
Category : Marine biology
Languages : en
Pages : 1362

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Reprints from various publications.

Author:
Publisher:
ISBN:
Category : Mines and mineral resources
Languages : en
Pages : 350

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Author: Maximus Theodorus Otten
Publisher:
ISBN:
Category : Diabase
Languages : en
Pages : 208

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Author: Esper Signius Larsen
Publisher: Geological Society of America
ISBN: 0813710294
Category : Science
Languages : en
Pages : 201

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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.

Author: Douglas M. Morton
Publisher:
ISBN: 9780813712116
Category : Baja California (Mexico : Peninsula)
Languages : en
Pages : 758

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"This book includes petrology, geochronology, and regional aspects of individual plutons, as well as evolution of the Peninsular Ranges batholith. Several chapters deal with geophysical, chemical, and isotopic based interpretations of the genesis and evolution of the batholith."--Provided by publisher.

Author: ATHERTON TARNEY(EDS)
Publisher: Springer Science & Business Media
ISBN: 1468405705
Category : Science
Languages : en
Pages : 234

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This book is for undergraduates, postgraduates and research workers who wish to gain an insight into present ideas and speculations on the origin of granite batholiths. It is a summary of the proceedings of a one-day meeting of the Geochemistry Group of the Mineralogical Society held at the University of liverpool on the 2nd May 1979, entitled The Origin of Granite Batholiths: Geochemical Evidence. It was felt that relevant new geochemical and isotopic data with associated field and petrological observations would be helpful in clarifying the main issues connected with the origin of granitic rocks. The speakers who participated contri buted a wealth of data and ideas to the problem, based on many years' experience of granitic rocks in various parts of the world. The popularity of the meeting indicated that a summary of the talks might be welcomed by a wider audience; hence this book. For reasons of length and cost, authors have been limited to presenting only the essential results necessary to develop their arguments and ideas. The comprehensive reference list will, however, assist those who wish to pursue specific aspects in greater detail. Inevitably, the cost and speed of publication may have resulted in some errors and inconsistencies which would not have occurred in a book produced over a longer time-span, but the editors hope that the rapid and up-to-date publication will offset this. The controversy over the origin of granite is as old as the science of geology.

Author: K. K. Sharma
Publisher:
ISBN:
Category : Geochemistry
Languages : en
Pages : 216

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