Flow and Transport During Contact Metamorphism and Hydrothermal Activity: Examples from the Oslo Rift

Jamtveit, Bjørn; Grorud, Hans Fredrik; Ragnarsdóttir, Kristín Vala

doi:10.1007/978-94-009-1533-6_4

Cited by 3 publications

(2 citation statements)

References 55 publications

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“…This is similar to the results of Voicu et al (2000), who found that Nd isotope compositions within a gold deposit hosted in granitoid rocks (with surrounding andesites and basalts) reflected the source of the mineralising fluid, while Sr isotopes had become rock buffered. In comparison, Jamtveit et al (1997) found that a skarn hosted in limestones and shales showed significant Sr isotope variation, yet little Nd isotope variation. It is likely that different hydrothermal systems will have different transport characteristics for Sr and Nd, depending on the composition of host rocks, and the composition and complexa-tion of Sr and Nd in the hydrothermal fluid (Gammons et al, 1996;DePaolo and Getty, 1996;DePaolo, 2006).…”

Section: Discussionmentioning

confidence: 86%

Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology

et al. 2009

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The 147 Sm-143 Nd isotope system may be used to determine the age of hydrothermal vein growth for single veins, or sets of veins, providing that the minerals in these veins formed from a hydrothermal fluid with initially homogeneous 143 Nd/ 144 Nd. In this study, we determined the 147 Sm-143 Nd, 87 Sr/ 86 Sr, δ 13 C and δ 18 O isotopic composition of 9 calcite and fluorite veins (comprising 12 samples in total) that form part of a lowtemperature (100-200°C) fault and fracture hosted hydrothermal system, in the eastern Lachlan Fold Belt, Australia. The vein swarm is hosted by mid-Devonian limestones, which were folded around 350-325 Ma, with vein growth occurring during folding. The veins chosen for analysis yield homogeneous Sr isotopic compositions ( 87 Sr/ 86 Sr = 0.70851 ±0.00003) and δ 18 O isotope values (22.5 ± 0.1‰), which are similar to those of the host limestones. The homogeneity of Sr and O isotope compositions is attributed to the progressive reaction of fluids with host rock, with sufficient reaction occurring along discrete fluid flow pathways to fully equilibrate the fluids for these isotope systems. By contrast, 143 Nd/ 144 Nd isotope compositions for the same samples show more variation ( 143 Nd/ 144 Nd = 0.51259-0.51199), which significantly exceeds analytical error. In addition, calcite and fluorite from within the same vein have distinctly different age-corrected Nd isotope compositions. Accordingly, it is likely that fluorite and calcite precipitated from different fluids. This study indicates that apparently synchronous vein-forming fluids, as suggested by structural relationships, may have diverse isotopic characteristics even over relatively small scales, reflecting variable equilibration of the fluids with the host-rocks. Incomplete equilibration or mixing, resulting in a range of initial 143 Nd/ 144 Nd compositions, is likely to be a common characteristic of fracture-hosted hydrothermal systems, compromising attempts to determine ages using Sm-Nd isochrons. The formation of veins with essentially identical Sr and O isotope compositions, yet diverse initial 143 Nd/ 144 Nd ratios, means that Sr and O isotopes cannot be used to identify suitable samples for Sm-Nd geochronological studies.

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Section: Discussionmentioning

confidence: 86%

Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology

et al. 2009

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“…The skarn samples have previously been described by Jamtveit et al [1993, 1995, 1997], who focused on the origin of oscillatory zoned grossular‐andradite (grandite) garnets in these rocks and concluded that the most Fe‐rich zones were formed during periods of rapid crystal growth triggered by influx of external fluids from a neighboring intrusion. Petrographic observations indicate that the skarn magnetite is formed simultaneously with the andradite garnets at temperatures and pressures of T = 350–400°C, P = 50–100 MPa [ Jamtveit et al , 1997]. Figure 1a shows a reflected light optical image of a section of a skarn sample dominated by grandite garnets, and millimeter‐sized magnetite grains.…”

Section: Samplesmentioning

confidence: 99%

Magnetic field visualization of magnetic minerals and grain boundary regions using magneto‐optical imaging

et al. 2007

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[1] Magneto-optical imaging based on the Faraday effect has been used to characterize magnetic minerals embedded in a nonmagnetic matrix. We have studied magnetite grains and magnetite-magnetite grain boundary regions in samples of skarns and serpentinites. Distributions of the remanent magnetic field were measured across at the surface of polished thin sections kept at room temperature. The magneto-optical images resolve directly magnetic structures on length scales ranging from millimeter down to micrometer, thereby revealing the shape and arrangement of the magnetite grains and allow determination of the grain magnetization. We find that (1) for the skarns the intergrain interactions do not affect the magnetic properties of magnetite grains within 0.6-60 mm of each other, while the saturation remanence decreases weakly with increasing grain size from 40 mm to 0.6 mm, and (2) for the serpentinites the magnetic properties of the stripes are size-dependent due to variations in chemical composition.

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Metamafic dyke and sill swarms in the Dom Feliciano Belt: Insights for post-collisional strike-slip tectonics and fluid-assisted metamorphism

Hoerlle

Remus

Dani

2022

Precambrian Research

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Flow and Transport During Contact Metamorphism and Hydrothermal Activity: Examples from the Oslo Rift

Cited by 3 publications

References 55 publications

Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology

Sm–Nd, Sr, C and O isotope systematics in hydrothermal calcite–fluorite veins: Implications for fluid–rock reaction and geochronology

Magnetic field visualization of magnetic minerals and grain boundary regions using magneto‐optical imaging

Metamafic dyke and sill swarms in the Dom Feliciano Belt: Insights for post-collisional strike-slip tectonics and fluid-assisted metamorphism

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