Bulletin of the United States Geological SurveyThe Survey., 1908 - Geology |
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abundant accessory actinolite Alaska amphibole arsenopyrite associated augite axinite bed rock Bering biotite boron Brooks Mountain Buck Creek calcite Cape Mountain Cassiterite Creek Cassiterite lode cassiterite occurs cent chalcopyrite cleavage coarse Collier color consists constituent contact rocks copper crystals danburite Ear Mountain embedded feldspar fluorite formation forms gangue garnet grains granite granite contact granite mass granular gravels hornblende hornfels hulsite inches thick intergrown intrusion iron lime-silicate limestone limestone adjoining locally Lost River magmatic magnetite marmorized metamorphism metasomatic metasomatic alteration microscope miles numerous orbules oxide paigeite pegmatite phenocrysts placer plagioclase pneumatolytic Port Clarence Port Clarence limestone prisms produced pyrite pyroxene quartz porphyry dikes quartz stringers radial groups scheelite schists seams Seward Peninsula shaft slates small amount sphalerite stanniferous stannite stream tin surface thin section Tin City Tin Creek tin deposits tin region topaz tourmaline tremolite U. S. Geol veinlets vesuvianite vicinity white mica wolframite York region zinnwaldite zone
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Page 12 - Collier, AJ, Reconnaissance of the northwestern portion of Seward Peninsula, Alaska: Prof. Paper US Oeol.
Page 12 - Some beds of fine-grained dolomite occur in the Port Clarence formation, but on account of their close resemblance to the prevailing dense-textured limestones their quantitative abundance is not known. Occasionally there occur interbedded with the normal Port Clarence limestones strata which show numerous small prisms of tremolite in random orientation. This is the highest degree of metamorphism displayed by the formation, except for purely local manifestations surrounding granitic intrusives. The...
Page 10 - Alaska. Prof. Paper No. 1, 1902, pp. 1-120. COLLIER, AJ A reconnaissance of the northwestern portion of Seward Peninsula, Alaska.
Page 50 - An energetic metasomatic alteration has accompanied the [formation of the] veinlets, and cassiterlte is locally observed in them, but nothing in the nature of a stanniferous stockwork has been formed. The tin ore found in the quartz porphyry dike is associated with irregular seams and stringers of quartz and lithia mica. Cassiterite occurs both in the stringers and as an impregnation of the altered dike adjoining the stringers. Where the veinlets are absent the quartz porphyry contains no casslterite...
Page 7 - Tin deposits of the York region, Alaska: Bull. US Geol. Survey No. 229, 1904.
Page 25 - SnO2) are probably not worth exploitation. The lode-tin deposits are genetically associated with the granitic intrusives, and on account of the abundance of limestone in the region the Seward Peninsula tin occurrences possess a number of unique and distinctive features. A variety of pneumatolytic contact rocks have been produced around the margins of the granites, and certain of these contain the iron-tin borates (hulsite and paigeite) as essential constituents. The resemblance of numerous heavy...
Page 25 - Placer tin is known to be widely distributed in the streams of Seward Peninsula," and has been found in some of the gold placers near Nome, but in amounts that are commercially unprofitable. Cassiterite is the only mineral that is likely to prove of economic value as a source of tin. Stannite is also known to occur, but at one locality only, where it is associated with galena in a remarkable argentiferous wolframite-topaz ore. Two new tin minerals (magnesian iron-tin borates) have been discovered,...
Page 7 - ... concentrates, all of which, except a few tons from lode deposits, came from the stream tin of Buck Creek. The...
Page 12 - Clarence, where it occupies an area of 1.400 square miles. Here it comprises a thick volume of thinbedded limestones of dense texture, generally unaffected by metamorphism. Four types of rock can be discriminated — an ash-gray variety, a dark lead-gray variety, magnesian and tremolitic phases, and an argillaceous banded variety. The first two are the commonest types, and occur together in interstratified beds. The dark lead-gray limestone forms massive beds up to 6 feet thick, but the ash-gray...
Page 29 - In addition to the paigeite, considerable tourmaline and minor amounts of chalcopyrite and magnetite are visible. Under the microscope the rock resolves itself into a confused intergrowth of zonally banded tourmaline, calcite, vesuvianite, zoisite, paigeite, fluorite, and accessory phlogopite, chalcopyrite, and magnetite. The paigeite is embedded in the various other constituents in trichite-like forms,