Coal metamorphism in the Anthracite-Crested Butte quadrangles, Colorado

Dapples, E. C.

doi:10.2113/gsecongeo.34.4.369

Cited by 23 publications

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“…The coking and anthracitization of coal by intrusions provides an interesting study, since laboratory experiments can give the variations of volatile content with temperature [McFarland, 1929]. Dapples [1939] attempted to calculate contact temperatures in this way, but his results are viiJared by an inconsistent application of Lovering's formulas [Jaeger, 1961].…”

Section: The Disturbance Of the Geothermal Gradientmentioning

confidence: 99%

Thermal effects of intrusions

Jaeger¹

1964

Reviews of Geophysics

259

142

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The mathematical theory used in calculating temperatures of intrusions is reviewed, primarily from the point of view of finding temperatures in the country rock outside them. It is shown that the detailed behavior inside the intrusion, for example the mechanism of solidification and the possible effects of convection, becomes progressively less important as the distance from the contact increases, so that at distances of one-quarter of the thickness or more the simple theory of Lovering is adequate. The theory for sheets, stocks, laccoliths, and some irregularly shaped bodies is given, together with the effect of dissimilar thermal conductivities. The effects of latent heat, convection, and the circumstances of intrusion are discussed. Applications to metamorphism, rock magnetism, and argon loss caused by heating by intrusions are reviewed. NOTATIONT, temperature (excess of temperature over some arbitrary level, which is usually taken to be the initial temperature of country rock). T1 to T2, range of solidification of magma, T• To, initial temperature of magma. L, latent heat of magma. K, thermal conductivity of country rock. p, density of country rock. c, specific heat of country rock. • = K/pc, diffusivity of country rock. K•, p•, c•, •, thermal properties of solidified magma if different from those of country rock. ' ' thermal properties of liquid magma if different from those of K2', p2• C2 • country rock. c2 -c2' -•-L/(T• -T2) , equivalent specific heat of magma. To • -To + L/c, equivalen• initial •empera•ure. To, initial con•ac• •empera•ure. 2d, thickness of an intrusive sheee• (or diameter of a cylinder or sphere). t, •ime a•er intrusion. • -Kt/d 2, dimensionless time or Fourier number. x, distance from midplane of an intrusive shee•. • -x/d. Units are cgs, calorie, and øC unless otherwise stated. 443 444 J. C. JAEGER 1. INTRODUCTIONMany attempts have been made to calculate the cooling-history of igneous intrusions. The problem is a fairly definite one: a mass of magma at a known temperature and of a known shape is iniected into country rock at a known temperature; the subsequent variation of temperature at any point is to be calculated. Fortunately, most rocks and magma have much the same thermal properties, so that a simple approximation may be obtained by assuming these to be constant and equal; hence (neglecting the effects of latent heat, convection, and other complicating factors to be discussed later), the problem reduces to the conduction of heat in an infinite medium with a prescribed initial distribution of temperature, and the solution can be written down immediately. Ingersoll and Zobel [1913] gave solutions for intrusive and extrusive sheets and for a spherical laccolith. Lovering [1935] gave complete information for the sheet and laccolith in graphical form, stressing the fact that such numerical information for these bodies could be given in terms of two dimensionless parameters, so that special cases need not be considered, as had been done by many authors. A full review of this phase of ...

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Section: The Disturbance Of the Geothermal Gradientmentioning

confidence: 99%

Thermal effects of intrusions

Jaeger¹

1964

Reviews of Geophysics

259

142

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“…Fingered sills were first described from various localities in the Spanish Peaks area of Colorado, U.S.A. (e.g. Hills, 1901;McFarlane, 1929;Dapples, 1939;Tweto, 1951), and later in South Dakota (Hurlbut & Griggs, 1939). More recently, Dutcher, Campbell & Thornton (1966) discussed Cretaceous coals from the Sopris-Purgatoire River area, Colorado, which have undergone extensive alteration due to the emplacement of cylindrical lamprophyre bodies (see their figures 7 and 8).…”

Section: Introductionmentioning

confidence: 99%

Coal—magma interaction: an integrated model for the emplacement of cylindrical intrusions

Kent

Ghose

Pasteels³

et al. 1992

Geol. Mag.

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Olivine-bearing lamproite magmas intruded into Permian coal seams in northeast India occur as root-like cylinder stockworks, extending for up to several kilometres up-dip along the bedding planes of their sedimentary host. Clusters of eight or more conduits are typical, linked by thin tubular cross-branches. Cylindrical geometry may arise by injection of hot, low-viscosity fluid through a slot, with the development of multiple tube-like instabilities at the interface between the moving fluid and a higher-viscosity host. This behaviour appears more complex than the models of Chouke, van Meurs & van der Pod, and Saffman & Taylor, which predict the development of a single dominant tube in porous or layered flow. Cylinder emplacement may be an essentially passive process, in which the sediment column is reduced by expulsion of heated pore fluids at the head of the moving intrusion, creating a space into which the melt can propagate. Generation of a superheated vapour envelope by non-nucleated film boiling of these fluids around the hot lamproite magma (the Leidenfrost effect) allows melt flow to be maintained in a lengthening tube thermally insulated from the surrounding coal, in a manner analogous to submarine lava tubes. Cooling of the magma through the Nukiyama temperature (the temperature at which maximum evaporation of the heated fluid occurs) may give rise to violent surface boiling and the formation of large vapour bubbles at the magma–coal interface. Implosion of these bubbles could then result in the formation of shock breccias, comparable to hyaloclastites produced by bubble or surface film collapse in the vicinity of pillow lava tubes. The operation of such a process around lamproite magma is suggested by the presence of complex breccias composed of highly fragmented coal, sandstone, and lamproite, at the termini of certain cylinders.Surface and subsurface exposures of the cylinders reveal the presence of a carbonate–chlorite–clay halo surrounding each intrusion, resulting from the alteration of mafic mineral phases by fugitive volatiles released from the protective vapour jacket. The coal seams proximal to intrusion clusters are relatively undeformed, with no evidence of assimilation by the invading melts. The coals have experienced extensive carbonization, probably as a result of slow conductive heating from the cooling lamproite bodies, or fluids derived therefrom. Field observations indicate that these thermal effects are not merely confined to the coal–melt interface, but occur for some considerable distance away from the intrusions, producing large areas of naturally coked coal.

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“…Most basic magmas crystallize at temperatures of about 900 to 1200 °C (Macdonald, 1972;Hyndman, 1985). High levels of thermal maturity and unusual thermal maturity profiles in mudrocks and coals that have been invaded by hot igneous intrusions have been widely reported (Briggs, 1935;Dapples, 1939;Dutcher and others, 1966;Schopf and Long, 1966;Bostick, 1971;Dow, 1977;Peters andothers, 1978,1983;others, 1978,1981;Dypvik, 1979;Perregaard and 1979; Bostick and Pawlewicz, 1984;Clayton and Bostick, 1985;Niem and Niem, 1985).…”

Section: Geologic Significance Of High Thermal Maturities and Paleote...mentioning

confidence: 95%

Preliminary report on petroleum source potential and thermal maturity of the Lospe Formation (lower Miocene) near Point Sal, onshore Santa Maria Basin, California

Stanley¹,

Pawlewicz²,

Vork³

et al. 1995

Open-File Report

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The Lospe Formation is an 830-m-thick sequence of sedimentary and minor volcanic rocks at the base of the onshore Neogene Santa Maria basin of central California. Eighteen outcrop samples (14 from lacustrine and shallow-marine mudstones of the Lospe Formation, and 4 from bathyal marine shales of the overlying Point Sal Formation) were collected from a measured stratigraphic section at North Beach (informal name) near Point Sal, and analyzed using Rock-Eval pyrolysis and vitrinite reflectance. The Rock-Eval data indicate that mudstones of the Lospe are low in organic carbon (range 0.18 to 0.80 weight percent, mean about 0.35 percent), and therefore are generally poor potential source rocks of petroleum. In contrast, shales of the Point Sal Formation exhibit much higher total organic carbon (range 1.47 to 3.63 weight percent, mean about 2.4 percent), and therefore are good to very good potential source rocks. These results should be regarded as preliminary because only a small number of samples were analyzed, and because interpretation of the data is complicated by weathering effects, relatively high thermal maturity, and evidence of migrated bitumen in some samples.Vitrinite reflectance values (range 0.68 to 1.56 percent RQ, mean 1.29 percent RO) and calculated maximum burial temperatures (range 106 °C to 192 °C, mean 172 °C) of the Lospe and Point Sal Formations in the North Beach section are the highest ever reported for Neogene rocks of the onshore Santa Maria basin. These high values can be explained by a combination of burial heating plus a local heat source such as a nearby gabbro sill and (or) a high-temperature hydrothermal system. The local heating event is poorly dated but probably late early or early middle Miocene, and may have stimulated thermal generation of oil and gas from organic-rich strata of the Point Sal Formation.1 Above base of Lospe Formation in the measured stratigraphic section at North Beach. Numerous normal(?) faults of unknown displacement probably have removed parts of the section (Johnson and Stanley, 1994).

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Coal metamorphism in the Anthracite-Crested Butte quadrangles, Colorado

Cited by 23 publications

References 0 publications

Thermal effects of intrusions

Thermal effects of intrusions

Coal—magma interaction: an integrated model for the emplacement of cylindrical intrusions

Preliminary report on petroleum source potential and thermal maturity of the Lospe Formation (lower Miocene) near Point Sal, onshore Santa Maria Basin, California

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