| Abstract: | Fluid inclusions in quartz and calcite of the Proterozoic Stripa granite, central Sweden, demonstrate that the rock and its fracture fillings have a complex evolutionary history. The majority of inclusions indicate formation during a hydrothermal stage following emplacement of the Stripa pluton. Total salinities of quartz inclusions range from 0-18 eq.wt% NaCl for unfractured rock and from 0-10 eq.wt% for fractured rock. Vein calcites contain up to 25 eq.wt% NaCl but the inclusion size is larger and the population density is lower. Homogenization temperatures are 100-150??C for unfractured rock and 100-250?? for fractured rock. Pressure corrections, assuming immediate post-emplacement conditions of 2 kbar, give temperatures about 160??C higher. Measurements of fluid-inclusion population-densities in quartz range from about 108 inclusions/cm3 in grain quartz to 109 inclusions/cm3 in vein quartz. Residual porosity from inclusion densities has been estimated to be at least 1% which is two orders of magnitude greater than the flow porosity. Breakage and leaching of fluid inclusions is proposed as an hypothesis for the origin of major solutes (Na-Ca-Cl) in the groundwater. Evidence for the hypothesis is based on (1) mass balance-only a small fraction of the inclusions need to leak to account for salt concentrations in the groundwater, (2) chemical signatures- Br Cl ratios of fluid inclusion leachates (0.0101) match those ratios for the deep groundwaters (0.0107), (3) leakage mechanisms-micro-stresses from isostatic rebound or mining activities acting on irregular-shaped inclusions could cause breakage and provide connection with the flow porosity, and (4) experimental studies-water forced through low permeability granites leach significant quantities of salt. This hypothesis is consistent with the available data although alternate hypotheses cannot be excluded. ?? 1989. |
| Genre: | Article |
| ProdID: | 70015470 |
| Citation Author: | Nordstrom, D. K.; Lindblom, S.; Donahoe, R. J.; Barton, C. C. |
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| Citation End Page: | 1755 |
| Citation Issue: | 8 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geochimica et Cosmochimica Acta |
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| Citation Number Of Pages: | 15 |
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| Citation Search Results Text: | Fluid inclusions in the Stripa granite and their possible influence on the groundwater chemistry; 1989; Article; Journal; Geochimica et Cosmochimica Acta; Nordstrom, D. K.; Lindblom, S.; Donahoe, R. J.; Barton, C. C. |
| Citation Start Page: | 1741 |
| Citation Volume: | 53 |
| Citation Year: | 1989 |
| Type: | citation/reference |
| Text: | Fluid inclusions in the Stripa granite and their possible influence on the groundwater chemistry; 1989; Article; Journal; Geochimica et Cosmochimica Acta; Nordstrom, D. K.; Lindblom, S.; Donahoe, R. J.; Barton, C. C. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1989 00:00 -0600 |
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