Optical determination of the An-content of plagioclases twinned by Carlsbad-law; a revised chart

Tobi, A. C.; Kroll, Herbert

doi:10.2475/ajs.275.6.731

Cited by 7 publications

(3 citation statements)

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“…The plagioclase phenocrysts are, as a rule, strongly zoned. The anorthite contents, approximated optically (Tobi & Kroll, 1975), vary between An 80 and An 60 in the cores, to between An 60 and An 40 in the rims and in the groundmass crystals. Outlying values of An 40 _ 20 were found in an altered dolerite.…”

Section: Basaltic and Doleritic Rocksmentioning

confidence: 99%

Provenance of coarse ice-rafted detritus near the SE Greenland margin

Linthout

Troelstra

Kuijpers

2000

Netherlands Journal of Geosciences

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The provenance of coarse-grained ice-rafted detritus has been studied, based on material collected from the SE Greenland margin.The sediment was sampled by a 1.5 m 3 video-grab from 1256 m water depth. The fraction > 1cm was macroscopically investigated and a thin-section analysis was made. The results clearly show that East Greenland north of the Denmark Strait is the source region of the material sampled. The main provenance is from areas adjoining Kangerdlugssuaq Fjord, Blosseville Kyst, Scoresby Sund, Kong Oskar Fjord, and Kejser Franz Joseph Fjord. It can thus be demonstrated that significant ice-stream activity and iceberg calving occurred there. Present-day iceberg production is mainly concentrated to the Scoresby Sund, but the other areas apparently represent locations of larger ice-stream activity during periods prior to the Holocene.More generally, it can be concluded that southerly surface-water flow similar to the present East Greenland Current must also have occurred prior to the Holocene. Although either North America (Canada) or Scandinavia -or both -are generally referred to as important regions for the provenance of ice-rafted detritus, we conclude that (East) Greenland may have been an important source for (late) glacial North Atlantic ice-rafted detritus production as well.

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Section: Basaltic and Doleritic Rocksmentioning

confidence: 99%

Provenance of coarse ice-rafted detritus near the SE Greenland margin

Linthout

Troelstra

Kuijpers

2000

Netherlands Journal of Geosciences

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“…The al bite twins were pres ent in the thin sec tion. The plagioclase compo si tions (an or thite con tents) were es ti mated by the MichelLévy Method (Tobi and Kroll 1975;Nesse 1991).…”

Section: Ap Pa Ra Tus and Pro Ce Duresmentioning

confidence: 99%

An Experimental Petrological Study of Gabbro in Chintan, Taipei County, at Atmospheric Pressure

Hsu¹,

Liu²,

Iizuka³

2010

Terr. Atmos. Ocean. Sci.

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A gab bro from Chintan, Sindian, was sub jected to ex per i ments at at mo spheric pres sure to study the frac tional crys tal li za tion of the gabbroic melt. The range of ex per i men tal tem per a tures was from 1120 to 1262°C, and the du ra tions were from about 16 to 150 hours. The min eral phases and the glass com po si tions in the quench ing prod ucts were analyzed with the SEM-EDS.The ex per i men tal re sults showed that the liquidus tem per a ture of the gab bro of Chintan is 1261°C. Fe-Ti ox ides crys tal lized at 1261°C. Plagioclase and chro mite crys tal lized at 1233 and 1196°C, re spec tively. Fi nally, pyroxene crys tal lized at 1178°C. The sol i dus tem per a ture is es ti mated to be about 1110°C and the melt ing in ter val is about 151°C. By com par ing the re sults of the runs with Au 75 -Pd 25 cap sules, the iron loss of melt to the plat i num en ve lopes at 1238°C over 18 hours can be neglected.The frac tional crys tal li za tion of the gabbroic melt at at mo spheric pres sure is con trolled by iron-ti ta nium ox ides, plagioclase, chro mite, and pyroxene. The dif fer en ti a tion trend of the gabbroic melts moves around in the cen ter of the AFM di a gram and can not fractionate into microsyenitic and al kali feld spar syenitic melts on the ground.

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“…Plagioclase composition was determined using the tables of Tobi and Kroll (1975). Mafic minerals were determined using Durrell (1949) and Deer, Howie, and Zussman (1966).…”

mentioning

confidence: 99%

Petrology of the Bull-of-the-Woods intrusive complex

Jackson¹

2000

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The Bull-of-the-Woods intrusive cbmplex consists of a cluster of dikes, sills, and irregular stocks, ranging in composition from pyroxene and/or hornblende andesite, dacite, diorite, to quartz diorite. lhese intrusi6ns were emplaced at shallow depth within the Sardine Formition, 1.72-3.10 percent weight Na; 3.27-5.57 percent weight Fe; 8-140 ppm Cr; 14.5-29.6 ppm Co; 11.44-21.00 ppm Sc; 10-17 ppm.Rb; 13-29 ppm La; 2.2-6.4 ppm Sm; 0.91-1.68 ppm ~u; 21";"58 ppm Sm; 170-900 ppm Ba; 1.0-7.6 ppm Th; 0.18-0.l,o ppm Lu; and ·1.6-6.7 ppm Hf.The narrow range of rare earth elements and the ratios of Fe/Co and Fe/Sc indicate that these rocks are comagmatic. The range of Sc is distributed in concentric, geographic zones of low, medium, and high concentrations through the area suggesting that mild gravity differentiation occurred in the parent magma body. The units were intruded along fissures in the host rock by forceful injection. The fine-grained rocks preceded intrusion of the coarse grained rocks, as indicated by crosscutting relationships. Broad, gentle deformation and propylitic alteration of the host rock suggests that a stock underlies the area.

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Optical determination of the An-content of plagioclases twinned by Carlsbad-law; a revised chart

Cited by 7 publications

References 0 publications

Provenance of coarse ice-rafted detritus near the SE Greenland margin

Provenance of coarse ice-rafted detritus near the SE Greenland margin

An Experimental Petrological Study of Gabbro in Chintan, Taipei County, at Atmospheric Pressure

Petrology of the Bull-of-the-Woods intrusive complex

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