Geochemistry of volcanic rocks in Barton and Weaver peninsulas, King George Island, Antarctica: Implications for arc maturity and correlation with fossilized volcanic centers

2004 ◽  
Vol 8 (1) ◽  
pp. 11-25 ◽  
Author(s):  
Jeong Pil Yeo ◽  
Jong Ik Lee ◽  
Soon Do Hur ◽  
Byeon-Gak Choi
Keyword(s):  
Volcanic Rocks ◽  
King George Island

Geochemistry of a fossil hydrothermal system at Barton Peninsula, King George Island

1995 ◽  
Vol 7 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Chil-Sup So ◽  
Seong-Taek Yun ◽  
Maeng-Eon Park
Keyword(s):  
Hydrothermal System ◽  
Meteoric Water ◽  
Volcanic Rocks ◽  
King George Island ◽  
Sulphur Isotope ◽  
Alteration Zones ◽  
Vein Formation ◽  
Calcite Veins ◽  
Lead Zinc ◽  
Barton Peninsula

A fossil hydrothermal system on Barton Peninsula, King George Island, Antarctica, formed a series of lead-zinc- and pyrite + native sulphur-bearing epithermal quartz ± calcite veins, filling fault-related fractures in hydrothermally altered volcanic rocks of Eocene age. The lead-zinc veins occur within argillic hydrothermal alteration zones, whereas the pyrite + native sulphur veins are found within advanced argillic alteration zones. Fluid inclusion data indicate that the vein formation occurred at temperatures between about 125° and 370°C (sphalerite deposition formed at 123–211°C) from fluids with salinities of 0.5–4.6 wt.% eq. NaCl. Equilibrium thermodynamic interpretation of mineral assemblages indicates that the deposition of native sulphur in the upper and central portions of the hydrothermal system was a result of the mixing of condensates of ascending magmatic gases and meteoric water giving rise to fluids which had lower pH (<3.5) and higher fugacities of oxygen and sulphur than the lead-zinc-depositing fluids at depth. The δ34S values of sulphide minerals from the lead-zinc veins (δ34S = −4.6 to 0.7‰) are much higher than the values of pyrite and native sulphur from the pyrite + native sulphur veins (δ34S = −12.9 to −20.1‰). This indicates that the fluids depositing native sulphur had higher sulphate/H2S ratios under higher fo2 conditions. Sulphur isotope compositions indicate an igneous source of sulphur with a δ34SΣS value near 0‰, probably the Noel Hill Granodiorite. Measured and calculated δ18O and δD values of the epithermal fluids (δ18Owater = −6.0 to 2.7‰, δDwater = −87 to −75‰) indicate that local meteoric water played an important role for formation of lead-zinc and native sulphur-bearing quartz veins.

Thermal metamorphism of volcanic rocks on Barton Peninsula, King George Island, Antarctica

2002 ◽  
Vol 6 (4) ◽  
pp. 303-317 ◽  
Author(s):  
Hyeoncheol Kim ◽  
Moonsup Cho ◽  
Jong-Ik Lee
Keyword(s):  
Volcanic Rocks ◽  
King George Island ◽  
Thermal Metamorphism ◽  
Barton Peninsula

Isotope geochemistry of volcanic rocks from the Barton Peninsula, King George Island, Antarctica

2011 ◽  
Vol 22 (1) ◽  
pp. 40-51 ◽  
Author(s):  
Jeong Hwang ◽  
Xiangshen Zheng ◽  
Edward M. Ripley ◽  
Jong-Ik Lee ◽  
Dongbok Shin
Keyword(s):  
Isotope Geochemistry ◽  
Volcanic Rocks ◽  
King George Island ◽  
Barton Peninsula

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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