I. Control of Ore by Primary Igneous Structures: Porcher Island, British Columbia. II. Structural Petrology: Crestmore, California. III. The Geochemistry and Paragenesis of the Ores of the Cactus Mine, Kern County, California

Citation

Smith, Alexander (1947) I. Control of Ore by Primary Igneous Structures: Porcher Island, British Columbia. II. Structural Petrology: Crestmore, California. III. The Geochemistry and Paragenesis of the Ores of the Cactus Mine, Kern County, California. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KJSR-8F29. https://resolver.caltech.edu/CaltechTHESIS:01182018-144333841

Abstract

Part I: Mapping internal structures of an intrusive has proven of value in quarrying but only about a dozen examples appear in the literature wherein metalliferous deposits in intrusives were found to occupy features such as cross joints or marginal upthrusts e.g. (Emmons and Grout 1935), (Kerr 1936), (Barr and Gardner 1940). This study therefore is presented as an additional example of structural control of an ore deposit by primary igneous structures. The lode deposits described in this paper show a rigorous control by a relatively small primary flow structure, an arch of flow layers.

The area studied is the northwest portion of Porcher Island, B. C. (Fig. 1). The principal deposits are those of the Surf Point and Edye Pass Mines. These properties lie about 25 miles southwest of Prince Rupert, B. C., the western terminus of the northern branch of the Canadian National Railways.

Part II: The general strike of the metasediments in the area is N.15°W. with dips at medium angles to the northeast. The limestone deposits at Crestmore and Jensen quarries are, however, on minor folds whose axial planes strike N.70°E.

Structural features which pitch easterly at -50° are (1) the general dip of the sediments (2) the axial line of the folds in limestone (3) the flow lines and dip of flow layers in the Perris quartz diorite (4) the dip of flow layers in the other intrusives (5) the axis of the girdle maxima for calcite optic axes. This direction is thought to be the a tectonic axis.

Strong optic axes maxima normal to the tonalite contact indicate the intrusive was forcibly injected and that the magma exerted pressure normal to the contact on the limestone. An unusual feature in the quartz diorite is two sets of flow layers having in common the flow lines therein.

Part III: This thesis embodies the results of a laboratory investigation of the ores and mill products of the Cactus mine. The primary purpose was a study of the association and distinction of the metallizing solutions as shown by the occurrence of the gangue and ore minerals.

This investigation has been correlated with geological and structural studies of the Cactus mine which are presented by Mr. John T. Jordan (Master’s Thesis, California Institute of Technology, 1941).

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