The Elements of economic geology

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Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part I. Introduction

Collection:: Economics Books

THE SCOPE OF ECONOMIC GEOLOGY 9 horizonta] fissures due to the shrinkage of the rock during cooling, The floors are arranged like the rungs of a ladder, and such lodes are called ladder-lodes (Fig. 3). The typical ®Xamples are at Wood's Point in Victoria, where they Occur in dykes of hornblende-porphyrite in slate. As a fule the floors of a ladder-lode are confined to the igneous tock ; but where on solidification that rock froze firmly to the adjacent slate the shrinkage cracks and consequently ‘he quartz-floors extend into it. Contra-lodes (Fig. 4) are small lodes which cross a lode at a high angle, just as great faults are crossed by secondary Cross-course faults. If some lode material has been deposited along a cross-fault it is a metalliferous cross-course or contra Cu ¥ Cus F16. 3.—A LADDER-Lopg, F16. 4—A ConTra-Lobk. A ladder-lode in a dyke traversing A contra-lode (Pb) containing slate. In two cases the quartz- lead, formed along a fault floors are shown penetrating which has broken a copper along cracks into the slate. lode {Cu). lode ; if the cross-course be only filled with clay it is a cross- fluccan. Great faults may extend to depths of probably a hundred miles, and the fissure lodes doubtless extend far below the levels which can be reached by mining ; and some lodes, or series of associated lodes. may extend for hundreds of miles in length. Lodes are usually much longer than their thickness ; but those formed along the intersection of two fractures or in a solution channel are pipe-lodes or * ore chimneys,” as the Achilles lode of gold ore at Tarradale, Victoria, or the Harrington-Hickory Mine in Utah due to the replacement of limestone along a cross fissure by lead ore (Butler, USGS. Prof. Pap., 111, 1920, p. 517). Lodes in folded sedimentary strata are often isolated. and

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