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| Range, Colorado, have been converted to orthoclase in a zone around a Tertiary intrusive stock. This stock...stock, near the town of Eldor, is 2 miles across and sholvs fairly well exposed vertical contacts The...The microcline-orthoclase transition, the only major manifestation of contact metamorphism, was investigated...and an obliquity ranging from 0.84 to 0.93. The orthoclase from near the contact is always turbid, untwinned...be observed. Both the nature of the microcline-orthoclase transition and its distance from the contact |
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| E , HORNBLENDE AND POTASSIUM FELDSPAR FROM ELDORA, COLORADO G L E N N W. B E R G E R 1 Geophysics Division...contact with the ~60 m.y. old Eldora stock in the Front Range of Colorado. The aim was to distinguish,...original study of Hart [ 15] in the Eldora contact zone in Colorado. In essence then, one knows the timing...- S r whole-rock dates [16], intrusion of the Boulder Creek batholith and associated regional metamorphism...about ten major stocks. The intrusion of the Eldora stock (3 km in diameter) has been dated at about 60 |
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| THE NIICROCLINE-ORTHOCLASE TRANSFORI{ATION THE CONTACT AUREOLE OF THE ELDORA STOCK, COLORADO1 IN Tuouas...monzonite stock near Eldora, Colorado, were transformed from maximum microcline to orthoclase by contact...shorter distances the samples are composed of orthoclase and i n t e r m e d i a t ea l b i t e . Data...microcline to orthoclase within the aureole of contact metamorphism surrounding the Eldora stock (Colorado). Hart...kindly supplied the author with specimensfrom the Eldora traverse (Hart, 1964, Steiger and Hart, 1967 Fig |
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| have included: (1) a Tertiary stock into Precambrian gneiss; (2) a stock into ash flow tuff; (3) a rhyodacite...circulating hydrothermal system in basalt. 2. The Eldora stock--Idaho Springs Formation contact zone: a conductive...58-Myr.-old Eldora stock and Precambrian gneiss of the Idaho Springs Formation, Colorado, where previous...al., 1968). The samples were collected from the stock and from the Idaho Springs Formation at the contact...identical to that used by Hart et al. (1968). The fresh stock rocks range in composition from monzonite to granodiorite |
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| *1"k"*"»T: 7' Northern Front Range Mineral Belt, Colorado UJS. GEOLOGICAL SURVEY PROFESSIONAL PA3PER...Intrusives in the Northern Front Range Mineral Belt, Colorado By DOLORES J. GABLE U.S. GEOLOGICAL SURVEY ...intrusives in the northern Front Range mineral belt, Colorado. (Geological Survey professional paper 1280) Bibliography:...stocks Long Gulch stock ........... Bryan Mountain (Eldora) stock . . . Caribou stock ............. Rainbow...Audubon-Albion stock .................. Jamestown stock ..................... Bald Mountain stock ........ |
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| r ages of hornblende from the Snowbank granitic stock near the contact with the Duluth Gabbro in Minnesota...the basis of the kinetic studies. The Snowbank stock is 2.60 billion (109) yr old and was transgressed...contact of the early Tertiary Eldora stock in the Front Range, Colorado. The effect of heating on Rb-Sr...ages from the 2.6-billion yr granitic Snowbank stock and the surrounding metasedimentary rocks near the...whereas the temperature of intrusion of the Eldora stock (quartz monzonite) was about 800°C (HART, 1964) |
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| Alkali Feldspar within the Rader Creek Pluton, Boulder Batholith, Montana1 by ROBERT I. TILLING U.S. Geological...general petrographic and mineralogic study of the Boulder batholith, a wide range of variation in microscopic...the Rader Creek pluton contains, in addition to orthoclase, grid-twinned microcline of varying obliquity...Geological Survey. • In this paper, the term 'orthoclase' is used precisely in the sense of Wright & Stewart...Alkali feldspars of this study designated as 'orthoclase' on the basis of the b-c criterion of Wright |
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| by BRUCE R. DOE U.S. Geological Survey, Denver, Colorado INTRODUCTION T H E isotopic composition of lead...within an individual magmatic complex such as the Boulder batholith, and by at least one isotope ratio that...shallow. A large triangular region comprising the Colorado Plateau and the Basin and Range province has not...Walcott Tuff (Re 3) Eldora stock, feldspar (Ta 1) Eldora stock, feldspar (Ta 1) Albion stock, feldspar (Ta...0-37 Pb I0> /Pb !0< 17-940 17-770 18090 18-742 Colorado 19156 19-508 19124 18-980 18-908 18-895 18-920 |
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| in the Santa Rosa Range, Nevada, and the Eldora area, Colorado, with emphasis on pelitic rocks. A consistent...S a n t a Rosa Range, Nevada, a n d the Eldora area, Colorado. A c o m p a n i o n study, dealing principally...Phyllite + 2,000 Whole rock 14.9 (1) Sawtooth stock, other samples SR0-24 + 2,000 Staurolite phyllite...Mineral ($O TM per mil 6 D per mil Santa Rosa stock S1~O-29F Granodiorite S1~O-29 A Migmatized hornfels...4• (2) 9.6• (2) 7.9 (I) 4.6 (1) -- 92 (1) Eldora traverse Biotite samples (HABT, 1964) C0A -- 5 |
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| occur, in alkaline minettes both microcline and orthoclase are present, and in alkaline microgranites and...the decrease of temperature below that of the orthoclase-microcline inversion and the presence of alkaline...rocks, microcline has been reported, from others, orthoclase. Velde's (1971) explanations are - in the author's...the two above mentioned types, one finds either orthoclase or microcline. This fact seems to be common,...igneous rocks (Stewart and Wright, 1974; Table 1. Orthoclase and Microcline Occurrence in Dykes of the Minette |
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| following string-perthitic metamorphim; three orthoclase (2) (ƒ¢=0.84-0.99, this superimposed minerals...transformed maximum are (ƒ¢=0, with been events orthoclase 2Vx=76•‹-83•‹) orthoclases (ƒ¢=0.86-0.92,...history of (Manuscript received, July, 1975) orthoclase. igneous and metamorphic rocks. This paper provides...extinction is mass, (0.00-0.57) are having orthoclase having the obliquities GEOLOGICAL characteristics...2Vx=76•‹-85•‹, These calcite granitiza into orthoclase ambiguous and action may may "dirty" abundant |
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| disordered half oi the range between high sanidine and orthoclase. Further Al-Si ordering is believed to have become...hydrothermally synthesizing both low-albite and orthoclase; he concludes that the presenceof peralkaline...the range betweenhigh sanidine and the sanidine-orthoclase boundary arbitrarily defined by Jones(1966).On...from the interior of the unit are closer to the orthoclase line. If we regard the relative positions of...percent of the distance between high sanidine and orthoclase. The relative degree of order of our sanidines |
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| high albite series) and Wright & Stewart (1968; orthoclase series). The exchnnge reactions were performed...albite and the orthoclase series; 2) 8' describes the variations between tile orthoclase and the sanidine...low albite series to 0.00 for a feldspar in the orthoclase series. The parameter ~' is defined as 9.063...this study lies between maximum mierocline and orthoclase; therefore, equation (2) applies and the feldspars...Spencer '15' Spencer 'U' + KCI Spencer 'B' SH 1070 Orthoclase (PSC-56KF) wt. % Or 20(060) • 20(204.)a 99 |
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| in the Battle Mountain Mining District, Lander County, Nevada GEOLOGICAL SURVEY PROFESSIONAL PAPER...in the Battle Mountain Mining District, Lander County, Nevada ByTED G. THEODORE, MILES L. SILBERMAN,...cents domestic postpaid or 45 cents GPO Bookstore Stock Number 2401-00333 CONTENTS Page Page Abstract...Distribution of normative quartz, plagioclase, and orthoclase in 11 chemically analyzed specimens ...........on retentivity of argon, biotite from Snowbank stock, 2.9 km from contact with Duluth Gabbro Complex |
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| from a contact aureole around a quartz monzonite stock are more closelv related, at least qualitatively...R. H., aNt Hanr, S. R. (1967) The microcline-orthoclase transition -116' 87 52, contact aureole. Amu...microcline-orthoclase transformation in the contact 117-736' Mineratr',52, Amer. the Eldora stock, Colorado |
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| Columbus, Ohio/USA Professor James L. Powell Department of Geology Oberlin College Oberlin, Ohio/USA ISBN-13:978-3-642-65369-8...and lepidolite) and the potassium feldspars (orthoclase and microcline). Minerals in pegmatites may contain...Killarney, 0.7184 Ontario, Canada Great Salt Lake, Utah, USA 0.7174 FAURE, HURLEY, and FAIRBAIRN (1963) HART...California (0.7070), British Columbia (0.7071), and Boulder (0.7066). These figures probably are within experimental...metamorphism on the Eldora Stock on the Idaho Springs Formation in the Front Ranges of Colorado. The Idaho Springs |
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| INTRUSIVE ROCKS OF COLORADO By Edward J. Young Prepared in cooperation with The Colorado Mining Industrial...Industrial Development Board and the Colorado Geological Survey This report is preliminary and has not been...intrusive rocks of Colorado » » » *«» In pocket Laramide-Tertiary intrusive rocks of Colorado By Edward...Laramide-Tertiary intrusive rocks in the State of Colorado, geologic age localities, mining districts, localities...This information is shown on the State map of Colorado (scale 1:500,000) accompanying this report. In |
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| orthopyroxene-bearing high-grade varieties with orthoclase megacrysts to mylonitic gneisses with microcline...Koitere K-feldspars vary from undeformed euhedral orthoclase megacrysts through partially recrystallized microcline...g, h θ, δ 2 i, j ϕ, σ Undeformed euhedral orthoclase megacrysts (transitional inversion to microcline...isotope composition of K-feldspars The undeformed orthoclase megacrysts in the Koitere granodiorites have...lines at 2.73 Ga. Therefore, we conclude that the orthoclase megacrysts have retained their initial compositions |
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| plagioclaseAn content effectsa shift of the plagioclase-orthoclase tie lines; (b) the fixed composition of muscovite...initial K-feldspar in all of these rocks was near orthoclase. (4) The absenceof any relation of Group I structural...observedin granitic rocks originally crystallized as orthoclase but invertedbecauseof a low Al/(f * Na) ratio...(1967) The synthesisof low albite. (abstr.) Pluton, Boulder Batholith, Montana. J. Petrologl,9, Amer. Geophys...microcline-orthoclase transformation in the contact aureole of the Eldora stock. orthoclase transition |
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| sequence. The potassic feldspars change from orthoclase in the borolanites through to microcline in the...matrix. The feldspar of the borolanites is an orthoclase, though some degree to triclinicity is often...29-30^° indicate that there is a complete from orthoclase to microcline. It has proved practicable to divide...3" but a rough estimate of the proportions of orthoclase and microcline can be made by comparison with...feldspars have orthoclase > 80 per cent ficial mixtures. group 2, group 3, 40-20 per cent orthoclase group 4 |
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| Geology and Ore Deposits of the Front Range Colorado By T. S. LO\'ERING and E. N. GODDARD GEOLOGICAL...in cooperation with the Colorado State Geological Survey Board and the Colorado Metal Mining Fund ~ oopr..._ Quartz diorite and associated hornblendite_ Boulder Creek granite _________________ _ Pikes Peak granite..._____________________ _ Copper deposits in Jefferson County __ _ F. M.D. property _____________ _ Malachite...________ _ Granite gneiss group ___________ _ Boulder Creek granite __________ _ Pikes Peak granite _____________ |
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| However, the presence in that gneiss of disordered orthoclase augen suggests its origin from pre-existing granite...pp Steiger RH, Hart SR (1967) The microcline-orthoclase transition within a contact aureole. Amer Mineral...The microcline-orthoclase transition in the contact aureole of the Eldora stock, Colorado. Amer Mineral |
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| albite and the potassic phase may be monoclinic orthoclase or triclinic microcline. Optical and X-ray studies...indicating monoclinic orthoclase alone and a double peak indicating both orthoclase and triclinic microcline...represents the conventional KA1Si3O8 'moleculer'), 'orthoclase' has a monclinic structure recognisable by X-rays...intermediate between orthoclase and maximum microcline, the monoclinic phase being orthoclase and the triclinic...Perhaps monoclinic specimens plot nearer to the orthoclase-albite boundary than the monoclinic-triclinic |
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| displays eastern part of Canada and the northeastern USA, the location of the map and also the lithotectonic...coarse grained with megacrysts of microperthic orthoclase. It also contains plagioclase (An20–10) and quartz...plutonic rocks of the northern Appalachian Mountains, USA and Canada: a geochemical method of terrane correlation...high-silica rhyolites of the Coso volcanic field, Inyo County, California. J Geophys Res 86:10223–10241 Bea F...vol 191. The Geological Society of America, Boulder, Colorado, pp 107–127 Clarke DB, MacDonald MA, Erdmann |
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| hornblendes from the contact aureole of the Eldora Stock, Colorado, U.S.A. Although the spectra revealed apparent-age...hornblende from the McClure Mountain Complex, Colorado, U.S.A., chosen as an interlaboratory standard...microcline lamellae undergo an inversion to an orthoclase structure before melting incongruently with the...biotite, hornblende and potassium feldspar from Eldora, Colorado. Earth Planet. Sci. Lett., 26: 387-408. 337 |
