Al and Ti contents of hornblende, indicators of pressure and temperature of regional metamorphism

Raase, P.

doi:10.1007/bf00383440

Cited by 286 publications

(151 citation statements)

References 9 publications

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“…The interpretation of the P/T ratio does not strongly depend on whether the interpretation of the zoning mechanism is completely correct. Comparing the RA-ll-D data to the results of Leake (1965), Raase (1974), Graham (1974), andLaird (1977), these amphiboles were formed under intermediate P/T conditions, similar to the regional metamorphic conditions of the Dalradian rocks in southwestern Scotland and of intermediate pressure areas in the regionally metamorphosed Paleozoic rocks of western New England. The overall mineral assemblage in RA-ll-L is appropriate for making the comparisons.…”

Section: Bsupporting

confidence: 67%

A study of mylonitic rocks from major fault zones : [annual technical report]

Anderson¹

1980

Open-File Report

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Section: Bsupporting

confidence: 67%

A study of mylonitic rocks from major fault zones : [annual technical report]

Anderson¹

1980

Open-File Report

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“…6). Although the compositional variations are large, the generally higher Al and Ti contents of amphibole in the lower dikes indicate higher temperatures of alteration than shallower in the dikes (Raase, 1974;Robinson et al, 1982). The general positive correlation of Cl contents with Al and Ti suggests increasing incorporation of Cl into amphibole at higher temperatures.…”

Section: Amphibolesmentioning

confidence: 99%

Mineralogy and Stable Isotopic Compositions of the Hydrothermally Altered Lower Sheeted Dike Complex, Hole 504B, Leg 140

Alt¹,

Evelyn²,

Erzinger³

1995

Proceedings of the Ocean Drilling Program, 137/140 Scientific Results

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Drilling during Legs 137 and 140 of the Ocean Drilling Program deepened Hole 504B, the only hole to penetrate through the volcanic section and into the underlying hydrothermally altered sheeted dike complex, by 438.1 m to a total depth of 2000.4 meters below seafloor. This paper presents the secondary mineralogy, bulk-rock sulfur contents, and stable isotopic (O, S) compositions, plus oxygen isotopic compositions of secondary minerals from the lower sheeted dike complex drilled during Legs 137 and 140. Various evidence indicates higher temperatures of hydrothermal alteration in the lower dikes than in the upper dikes, including: the local presence of secondary clinopyroxene in the lower dikes; secondary anorthite and hornblende in the lower dikes vs. mainly actinolite and albite-oligoclase in the upper dikes; generally increasing Al and Ti contents of amphibole downward in the dike section; and greater 18 O depletions of the lower dikes (δ 18 θ = 3.6-5.0‰) compared with the upper dikes. Early high-temperature alteration stages (T = 350°-500°C) resulted in 18 O depletions and losses of metals (Cu, Zn) and sulfur from the rocks. Local incorporation of reduced seawater sulfate led to elevated δ 34 S values of sulfide in the rocks (up to 2.5‰). Quartz + epidote formed in crosscutting veins at temperatures of 310°-320°C from more evolved fluids (δ 18 θ = l‰). Late-stage lower-temperature (~250°C) reactions producing albite, prehnite, and zeolites in the rocks caused slight 18 O enrichments, but these were insufficient to offset the 18 O depletions caused by earlier higher-temperature reactions. Addition of anhydrite to the rocks during seawater recharge led to increased S contents of rocks that had previously lost S during axial hydrothermal alteration, and to further increases in δ 34 S values of total S in the rocks (up to 12‰). Despite the evidence for seawater recharge to near the base of the sheeted dike complex, the paucity of late zeolites in the lower dikes suggests that late-stage, off-axis circulation was mainly restricted to the volcanics and shallowest dikes, or to localized high-permeability zones (faults) at depth.

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“…Complementary P-T estimates of the amphibole-rich unit were obtained using the thermometer based on the cation exchange reaction of edenite (Holland and Blundy, 1994). Thermobarometers based on the contents of Ti and Al (VI) in amphibole were not used because of the absence of Zo and Ep in our samples (Raase, 1974;Plyusnina, 1982;Hammarstrom and Zen, 1986).…”

Section: Thermobarometric Methodsmentioning

confidence: 99%