A comparative fluid inclusion study of the Waterville and Sangerville (Vassalboro) formations, south-central Maine

Saved in:
Online Access: Get full text
doi: 10.1007/s004100050022
Authors:Olsen, S. N.; Ferry, J. M.
Author Affiliations:Primary:
Johns Hopkins University, Department of Earth and Planetary Science, Baltimore, MD, United States
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 118(4), p.396-413. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1995
Note:In English. 64 refs.; illus., incl. 3 tables, geol. sketch map
Summary:Petrological and oxygen isotope data indicate that water-rich fluids infiltrated metasedimentary rocks of these two formations during peak metamorphism, and depleted Sangerville rocks in alkalis but not equivalent Waterville rocks. Fluid inclusion data from two outcrops, ∼ 1 km apart, one of the Waterville and the other of the Sangerville, suggest a cause for the geochemical difference between the two units. Postulated peak metamorphic inclusions, the texturally earliest of aqueous inclusions in the metasediments, approximate the water-rich compositions of peak fluids predicted by mineral-fluid equilibria, and have average salinity in the Sangerville formation ∼ three times that of equivalent Waterville inclusions. The higher salinity in the Sangerville fluids could explain the greater alkali depletion of these rocks. Probable pre-peak or prograde inclusions are preserved in metasediments as the texturally earliest carbonic inclusions which contain CO2, CH4, N2 ± H2O, as determined by microthermometry and Raman spectrometry. They have formed by breakdown of organic matter. Probable retrograde inclusions occur as texturally late aqueous inclusions in healed fractures with salinity range indistinguishable between the two formations. Synmetamorphic granitic dykes present in the two outcrops were ruled out as a source for fluids in metasediments because composition and density ranges of inclusions in dykes and metasediments are fundamentally different, and because there is no correlation between the abundance or composition of inclusions in a sample and the proximity to dykes. Isochores for many of the inclusions in both metasediments and dykes are not consistent with the inferred P-T conditions of their trapping, but intersect at ∼ 300-400°C and 1 to 2 kbar. These intersections probably resulted because inclusion densities continued to equilibrate during uplift and cooling until quartz became rigid. The present densities are those at the last equilibration, not at the time of trapping. In contrast, the clear distinctions in inclusion compositions between dykes and between dyke and country rock show that the original compositional differences generally have been preserved. [P.Br.]
Subjects:Chemical composition; Cooling; Density; Dikes; Fluid inclusions; Framework silicates; Geologic thermometry; Inclusions; Intrusions; Metamorphic rocks; Metamorphism; Metasedimentary rocks; P-T conditions; Paleozoic; Quartz; Retrograde metamorphism; Sangerville Formation; Silica minerals; Silicates; Silurian; Uplifts; Waterville Formation; Maine; United States; South-central Maine
Abstract Numbers:95M/3173
Record ID:1995034550
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Tags: Add Tag
No Tags, Be the first to tag this record!
Be the first to leave a comment!
You must be logged in first