The dolerite-chalk contact of Scawt Hill, Co. Antrim. The production of basic alkali-rocks by the assimilation of limestone by basaltic magma (With Plates XVII and XVIII.)

Tilley, C. E.; Harwood, H. F.

doi:10.1180/minmag.1931.022.132.02

Cited by 40 publications

(11 citation statements)

References 4 publications

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“…Spurrite, Ca 5 (SiO 4 ) 2 (CO 3 ), a nesosilicate typical of high‐temperature contact metamorphism of siliceous limestones (e.g., Tilley ; Tilley and Harwood ; Walter ; Joesten ; Marineca et al. ; Pascal et al.…”

Section: Resultsmentioning

confidence: 99%

The reaction of carbonates in contact with laser‐generated, superheated silicate melts: Constraining impact metamorphism of carbonate‐bearing target rocks

Hamann

Bläsing

Hecht

et al. 2018

Meteorit & Planetary Scien

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We simulated entrainment of carbonates (calcite, dolomite) in silicate impact melts by 1‐bar laser melting of silicate–carbonate composite targets, using sandstone, basalt, calcite marble, limestone, dolomite marble, and iron meteorite as starting materials. We demonstrate that carbonate assimilation by silicate melts of variable composition is extremely fast (seconds to minutes), resulting in contamination of silicate melts with carbonate‐derived CaO and MgO and release of CO2 at the silicate melt–carbonate interface. We identify several processes, i.e., (1) decomposition of carbonates releases CO2 and produces residual oxides (CaO, MgO); (2) incorporation of residual oxides from proximally dissociating carbonates into silicate melts; (3) rapid back‐reactions between residual CaO and CO2 produce idiomorphic calcite crystallites and porous carbonate quench products; (4) high‐temperature reactions between Ca‐contaminated silicate melts and carbonates yield typical skarn minerals and residual oxide melts; (5) mixing and mingling between Ca‐ or Ca,Mg‐contaminated and Ca‐ or Ca,Mg‐normal silicate melts; (6) precipitation of Ca‐ or Ca,Mg‐rich silicates from contaminated silicate melts upon quenching. Our experiments reproduce many textural and compositional features of typical impact melts originating from silicate–carbonate targets. They reinforce hypotheses that thermal decomposition of carbonates, rapid back‐reactions between decomposition products, and incorporation of residual oxides into silicate impact melts are prevailing processes during impact melting of mixed silicate–carbonate targets. However, by comparing our results with previous studies and thermodynamic considerations on the phase diagrams of calcite and quartz, we envisage that carbonate impact melts are readily produced during adiabatic decompression from high shock pressure, but subsequently decompose due to heat influx from coexisting silicate impact melts or hot breccia components. Under certain circumstances, postshock conditions may favor production and conservation of carbonate impact melts. We conclude that the response of mixed carbonate–silicate targets to impact might involve melting and decomposition of carbonates, the dominant response being governed by a complex variety of factors.

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Section: Resultsmentioning

confidence: 99%

The reaction of carbonates in contact with laser‐generated, superheated silicate melts: Constraining impact metamorphism of carbonate‐bearing target rocks

Hamann

Bläsing

Hecht

et al. 2018

Meteorit & Planetary Scien

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“…There is an abundant literature describing the reactions between silicate magmas and carbonate rocks at the magmatic and early postmagmatic stages. In a pioneering study, Tilley & Harwood (1931) described reactions at a dolerite-chalk contact at Scawt Hill, Ireland. In the case of Vesuvius, the magmadolostone interactions have been documented, among produced by contact-metamorphism of dolomites (e.g., Bowman & Essene 1982).…”

Section: Geological Setting Of the Qandilite-bearing Skarnsmentioning

confidence: 99%

Qandilite From Vesuvius Skarn Ejecta: Conditions of Formation and Miscibility Gap in the Ternary Spinel - Qandilite - Magnesioferrite

Pascal

Fonteilles

Boudouma

et al. 2011

The Canadian Mineralogist

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Qandilite (Mg 2 TiO 4 ) and magnesioferrite occur in forsterite -spinel -calcite skarn ejecta from Mt. Vesuvius, Italy, with an exceptionally large compositional range that outlines the miscibility gap in the system spinel -qandilite -magnesioferrite (with a small amount of Fe 2+ ), at present solely determined on the spinel-qandilite binary at T > 1000°C. The analyzed spinelqandilite and spinel-magnesioferrite pairs are consistent with the solvus and tie-lines (except for a temperature offset) derived from the thermochemical model of spinel solid-solutions. Temperatures of formation in the range 650-700°C are inferred from the petrological study of the skarn-forming processes involved, which typically include two types of metasomatic reactions, i.e., formation of spinel -forsterite -calcite endoskarns by desilication of aluminosilicate bodies at the contact of dolostone wallrocks, and reaction of such pre-existing endoskarns with new influxes of magma ± fluid. Calculated phase-relations among qandilite, perovskite and geikielite show that qandilite with moderate magnesioferrite contents is the high-temperature Ti mineral stable in magnesian and extremely silica-deficient surroundings under oxidized conditions.

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“…Several of these plugs have intruded the chert (flint)-bearing Upper Cretaceous Ulster White Limestone Formation. The chert nodules have been hornfelsed by the dolerite producing a calcsilicate mineral assemblage (Tilley, 1929(Tilley, , 1930(Tilley, , 1933Tilley and Harwood, 1931;Tilley and Alderman, 1934;Tilley and Vincent, 1948;Sabine, 1975;Griffith and Wilson, 1982;Sabine et al, 1982Sabine et al, , 1985Mitchell, 2004). A field visit was undertaken to examine and sample the metamorphic aureoles around the dolerite plugs at Scawt Hill and Carneal Plug (Fig.…”

Section: Geological Setting Of the Natural Analogue Sites From Northementioning

confidence: 99%

Carbonation of borehole seals: Comparing evidence from short-term laboratory experiments and long-term natural analogues

Rochelle

Milodowski

2013

Applied Geochemistry

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It is crucial that the engineered seals of boreholes in the vicinity of a deep storage facility remain effective for considerable timescales if the long-term geological containment of stored CO 2 is to be effective. These timescales extend beyond those achievable by laboratory experiments or industrial experience. Study of the carbonation of natural Ca silicate hydrate (CSH) phases provides a useful insight into the alteration processes and evolution of cement phases over long-timescales more comparable with those considered in performance assessments. Samples from two such natural analogues in Northern Ireland have been compared with samples from laboratory experiments on the carbonation of Portland cement. Samples showed similar carbonation reaction processes even though the natural and experimental samples underwent carbonation under very different conditions and timescales. These included conversion of the CSH phases to CaCO 3 and SiO 2 , and the formation of a well-defined reaction front. In laboratory experiments the reaction front is associated with localised Ca migration, localised matrix porosity increase, and localised shrinkage of the cement matrix with concomitant cracking. Behind the reaction front is a zone of CaCO 3 precipitation that partly seals porosity. A broader and more porous/permeable reaction zone was created in the laboratory experiments compared to the natural samples, and it is possible that short-term experiments might not fully replicate slower, longer-term processes. That the natural samples had only undergone limited carbonation, even though they had been exposed to atmospheric CO 2 or dissolved HCO 3 -in groundwater for several thousands of years, may indicate that the limited amounts of carbonate mineral formation may have protected the CSH phases from further reaction. IntroductionAcceptable performance of the geological storage of CO 2 will need to be demonstrated in order to satisfy operational, regulatory and public acceptance criteria, and a key element of this will be the effectiveness of the seals preventing CO 2 migration. At a generic level, the occurrence of natural CO 2 accumulations demonstrates the containment potential of caprock materials that have not been penetrated by human activity over time periods measurable in 10

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The dolerite-chalk contact of Scawt Hill, Co. Antrim. The production of basic alkali-rocks by the assimilation of limestone by basaltic magma (With Plates XVII and XVIII.)

Cited by 40 publications

References 4 publications

The reaction of carbonates in contact with laser‐generated, superheated silicate melts: Constraining impact metamorphism of carbonate‐bearing target rocks

The reaction of carbonates in contact with laser‐generated, superheated silicate melts: Constraining impact metamorphism of carbonate‐bearing target rocks

Qandilite From Vesuvius Skarn Ejecta: Conditions of Formation and Miscibility Gap in the Ternary Spinel - Qandilite - Magnesioferrite

Carbonation of borehole seals: Comparing evidence from short-term laboratory experiments and long-term natural analogues

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