Abstract
THE State of Texas consists mainly of plains of Cretaceous and Cainozoic rocks which slope gradually eastward to the Gulf of Mexico. They are interrupted to the north-west of the city of Austin by an outcrop of pre-Cambrian rocks composed of granite, gneiss, and schist, and of some early Palaeozoic sediments, including Cambrian and Ordo-vician. These older rocks of Texas have been described in a bulletin by Mr. Paige, who has proved that they have been faulted up into their present position. These old rocks contain some iron ores, of which the Survey during its work in the region discovered thirty-two occurrences. Only three are sufficiently large to be of economic importance, and their value is still unproved. The ores are masses of magnetite; they occur in the schists and usually along the contact with the granites or in bands of rock crushed between parallel faults. The iron was originally deposited in marine sediments, and has been concentrated in consequence of the intrusion of the granites and diabases and of the faulting. The author, in concluding his discussion, quotes a passage from Van Hise attributing the origin of many ores to the materials of igneous rocks, and he inserts iron in the list given by Van Hise; but the case of iron is so different from the others that this addition is scarcely justified.
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References
“Mineral Resources of the Llano-Burnet Region, Texas, with an Account of the Pre-Cambrian Geology.” By S Paige . Bulletin 450, U.S. Geological Survey, Washington, 1911. Pp. 103 + v plates + 22 figs. “The Lander and Salt Creek Oil Fields, Wyoming.” The Lander Oil Field, Fremont County. By E. G. Woodruff . The Salt Creek Oil Field, Natrona County. By C. H. Wegemann Bulletin 452, U.S. Geological Survey, Washington, 1911. Pp. 87 + xii plates + 1 fig. “;A Geologic Reconnaissance in South-eastern Seward Peninsula and the Norton Bay–Nulato Region, Alaska.” By P. S. Smith and H. M. Edkin . Bulletin 449, U.S. Geological Survey, Washington, 1911. Pp. 146 + xiii plates + 15 figs. “Geology and Mineral Resources of the Nizina District, Alaska.” By F. H. Moffit and S. R. Capps . Bulletin 448, U.S. Geological Survey, Washington, 1911. Pp. iii + xii plates + II figs. “Contributions to Economic Geology.” (Short Papers and Preliminary Reports, 1909.) Part ii., Mineral Fuels. [M. R. Campbell, Geologist in Charge]. Bulletin 431, Washington, 1911. Pp. 254 + xii plates + 4 figs.
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G., J. Contributions to American Economic Geology 1 . Nature 90, 659–660 (1913). https://doi.org/10.1038/090659a0
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DOI: https://doi.org/10.1038/090659a0