Sten Lindblom

Fluid inclusions in the Stripa granite and their possible influence on the groundwater chemistry

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—BrCl 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.

Fossilized microorganisms associated with zeolite–carbonate interfaces in sub-seafloor hydrothermal environments

In this paper we describe carbon-rich filamentous structures observed in association with the zeolite mineral phillipsite from sub-seafloor samples drilled and collected during the Ocean Drilling Program (ODP) Leg 197 at the Emperor Seamounts. The filamentous structures are approximately 5 microm thick and approximately 100-200 microm in length. They are found attached to phillipsite surfaces in veins and entombed in vein-filling carbonates. The carbon content of the filaments ranges between approximately 10 wt% C and 55 wt% C. They further bind to propidium iodide (PI), which is a dye that binds to damaged cell membranes and remnants of DNA. Carbon-rich globular microstructures, 1-2 microm in diameter, are also found associated with the phillipsite surfaces as well as within wedge-shaped cavities in phillipsite assemblages. The globules have a carbon content that range between approximately 5 wt% C and 55 wt% C and they bind to PI. Ordinary globular iron oxides found throughout the samples differ in that they contain no carbon and do not bind to the dye PI. The carbon-rich globules are mostly concentrated to a film-like structure that is attached to the phillipsite surfaces. This film has a carbon content that ranges between approximately 25 wt% C and 75 wt% C and partially binds to PI. EDS analyses show that the carbon in all structures described are not associated with calcium and therefore not bound in carbonates. The carbon content and the binding to PI may indicate that the filamentous structures could represent fossilized filamentous microorganisms, the globules could represent fossilized microbial cells and the film-like structures could represent a microbially produced biofilm. Our results extend the knowledge of possible habitable niches for a deep biosphere in sub-seafloor environments and suggests, as phillipsite is one of the most common zeolite mineral in volcanic rocks of the oceanic crust, that it could be a common feature in the oceanic crust elsewhere.

Fossilized Microorganisms from the Emperor Seamounts: Implications for the Search for a Subsurface Fossil Record on Earth and Mars

We have observed filamentous carbon-rich structures in samples drilled at 3 different seamounts that belong to the Emperor Seamounts in the Pacific Ocean: Detroit (81 Ma), Nintoku (56 Ma), and Koko Seamounts (48 Ma). The samples consist of low-temperature altered basalts recovered from all 3 seamounts. The maximum depth from which the samples were retrieved was 954 meters below seafloor (mbsf). The filamentous structures occur in veins and fractures in the basalts, where they are attached to the vein walls and embedded in vein-filling minerals like calcite, aragonite, and gypsum. The filaments were studied with a combination of optical microscopy, environmental scanning electron microscopy (ESEM), Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Minerals were identified by a combination of optical microscopy, X-ray diffraction, Raman spectrometry, and energy dispersive spectrometry on an environmental scanning electron microscope. Carbon content of the filaments ranges between approximately 10 wt % and approximately 50 wt % and is not associated with carbonates. These results indicate an organic origin of the carbon. The presence of C(2)H(4), phosphate, and lipid-like molecules in the filaments further supports a biogenic origin. We also found microchannels in volcanic glass enriched in carbon (approximately 10-40 wt %) compatible with putative microbial activity. Our findings suggest new niches for life in subseafloor environments and have implications for further exploration of the subseafloor biosphere on Earth and beyond.

Weathering detected by Raman spectroscopy using Al-ordering in albite

Albite samples from Ontario, Canada, laboratory weathered in HCl solutions at pH 1 have been analysed and compared to unreacted mineral samples with the same crystal orientation using Raman microspectrometry. The study was focused on Raman bands reflecting Al-ordering because destabilisation of Al–O bonds with subsequent release of Al is well recognised to be a major factor in low pH dissolution of albite. Analyses of unweathered samples reveal that most bands in the albite spectra show variations in intensities for different crystal orientations in the wavenumber range 100 to 1200 cm−1. A well-defined crystal orientation is therefore essential to a successful investigation of weathered samples. Unweathered albite has two bands; 455 and 976 cm−1 in the spectrum normal to the (001) face, which have been related to Al-ordering in the structure. In spectra of weathered albite crystals, with the same orientation, the band most sensitive to alteration is 976 cm−1. This band is very strong for unreacted albite, but diminishes in intensity relative to the other bands at the initial stage of weathering. When dissolution continued, the structural information in the range 700 to 1200 cm−1 was completely lost, shown as a bandbroadening of a less organised structure, while the characteristic albite bands still could be observed in the range 100 to 600 cm−1.

Fluid evolution in gold‐bearing quartz veins associated with feldspar porphyry dikes at Vinliden in the Skellefte District, northern Sweden

Abstract The Vinliden gold mineralization is located in the northwest‐em part of the Skellefte District in northern Sweden. The mineralization consists of a number of gold‐bearing quartz veinlets in a greywacke sequence. The quartz veins have been emplaced in small‐scale second order fault and shear zones within one of the major fault structures, which transects the folded supracrustal pile in the Skellefte District The Vinliden gold occurrence is spatially related to feldspar porphyry dikes which have intruded the greywackes. Alteration zones with albite or sericite surround the quartz veinlets. The mineralization also includes a sulfide assemblage dominated by arsenopyrite and pyrrhotite. Aqueous and carbonic (CO2‐CH4) fluid inclusions in the quartz veinlets indicate initial deposition of quartz and an early generation of arsenopyrite at a temperature exceeding 400 °C in association with a pressure drop from 5 to 1 kbar. Secondary fracturing opened passageways and allowed fluid pressure to adjust to hyd...

Identification and implications of fight hydrocarbon fluid inclusions from the Proterozoic Bidjovagge gold-copper deposit, Finnmark, Norway

Carbonic fluid inclusions were observed in quartz-bearing veins at the Proterozoic Bidjovagge AuCu deposit within the Kautokeino greenstone belt in Norway, where mineralization occurred in oxidation zones of graphitic schists. A primary fluid inclusion zonation was observed with C02-rich fluid inclusions in the structural footwall of the deposit, and CH4-rich inclusions within the ore zone in the oxidation zone. Microthermometry of the primary hydrocarbon inclusions revealed 2 groups; (1) a group which homogenized between −125°C and the critical temperature of CH4 (−82.1°C), which indicated the presence of pure CH4, and (2) a group which homogenized between the critical temperature of CH4 and −42°C, which indicated the presence CH4 and higher hydrocarbons (HHC). Raman microprobe analyses of the first group confirmed the presence of CH4. The second inclusion group were fluorescent, and Raman spectra clearly displayed CH4,C2H6, and rarer C3H8 peaks. A typical feature of the Raman spectra were elevated baselines at the hydrocarbon peaks. Carbon peaks were also usually detected in each inclusion by Raman analysis. Bulk gas chromatography analyses of samples containing the first group (CH4) indicated the presence of CH4 and low concentrations of C2H6 and C3H8. Gas chromatography analyses of samples containing the second group (CH4 and higher hydrocarbons) confirmed the presence of CH4, and higher hydrocarbons such as C2H6 and C3H8 and also butanes. Based on the spacial zonation of hydrocarbons and the estimated PT conditions of 300 to 375°C and 2 to 4 kbars, the authors suggest an abiotic origin for the hydrocarbons. It is suggested that the hydrothermal fluids oxidized the graphitic schist, precipitated Cu and Au and formed light gas hydrocarbons.

Evidence of fracturing and fluid movements in granite from Finnsjön, Sweden, derived from inclusions in fracture-filling calcite and prehnite

Abstract Fluid inclusions in fracture fillings in a red homogeneous granite at Finnsjon, Sweden, indicate a complex history of fracturing and infilling, dissolution and redeposition in the last calcite phase. Three events of fluid activation were documented in the fractures: (1) deposition at 80°C from a solution with 17 eq. wt.% NaCl; (2) deposition at 135°C from 3.4 eq. wt.% NaCl solution; (3) deposition or rehealing at 100°C or lower from a fresh to brackish water solution. The inclusions frequently display metastable behavior with regard to vapor phase nucleation, indicating that formation at a low temperature may be a dominant event. This could mean deposition from alternately a circulated seawater and a subsurface brine. The fractures may have been active quite recently as shown by low-temperature freshwater inclusions and tectonic textures.

Putative Fossilized Fungi from the Lithified Volcaniclastic Apron of Gran Canaria, Spain

We report the discovery of fossilized filamentous structures in samples of the lithified, volcaniclastic apron of Gran Canaria, which were obtained during Leg 157 of the Ocean Drilling Program (ODP). These filamentous structures are 2-15 μm in diameter and several hundred micrometers in length and are composed of Si, Al, Fe, Ca, Mg, Na, Ti, and C. Chitin was detected in the filamentous structures by staining with wheat germ agglutinin dye conjugated with fluorescein isothiocyanate (WGA-FITC), which suggests that they are fossilized fungal hyphae. The further elucidation of typical filamentous fungal morphological features, such as septa, hyphal bridges, and anastomosis and their respective sizes, support this interpretation. Characteristic structures that we interpreted as fossilized spores were also observed in association with the putative hyphae. The fungal hyphae were found in pyroxene phenocrysts and in siderite pseudomorphs of a basalt breccia. The fungal colonization of the basalt clasts occurred after the brecciation but prior to the final emplacement and lithification of the sediment at ∼16-14 Ma. The siderite appears to have been partially dissolved by the presence of fungal hyphae, and the fungi preferentially colonized Fe-rich carbonates over Fe-poor carbonates (aragonite). Our findings indicate that fungi may be an important geobiological agent in subseafloor environments and an important component of the deep subseafloor biosphere, and that hydrothermal environments associated with volcanism can support a diverse ecosystem, including eukaryotes.

Organic geochemistry of lipids in marine sediments in the Canary Basin: Implications for origin and accumulation of organic matter

Abstract The Canary basin consists of the continental margin off the coast of Northwest Africa, the deep basin, the Madeira Abyssal Plain (MAP) and the volcanic Canary Islands. The continental margin has an area of upwelling marine productivity with special characteristics: (a) a wide shelf area, (b) a wide irregular zone of upwelling, and (c) proximity to a large dust source—the Saharan desert. The Canary Islands divide the continental slope into a northern area and a southern area of primary productivity and accumulation of organic matter (OM). Accumulation of marine OM in the northern area is augmented by input of Saharan dust containing adsorbed terrigenous OM. n -Alkane distributions show a pronounced maximum around C 29 and C 31 with a strong odd-to-even predominance typical of terrigenous OM. There are less pronounced maxima near C 15 -C 17 , indicating a recent marine origin for the OM. Fatty acids show carbon number distributions similar to the n -alkanes, with a higher content and substantially higher C 16 /C 26 ratios in near-surface sediments of the slope samples, which decrease with depth in the sediment. The above data from the slope sediments can be compared to the most recent organic turbidite “a” on the MAP. Turbidite “a” was emplaced about 1000 years ago, incorporating slope derived material representing a 200,000-year time period. TOC and biomarker signatures of sediments on the slope are comparable to turbidite “a”. Biomarker analyses of deeper sediments on the MAP show similar data continuing back to early Miocene. Comparison of recent seafloor surface biomarkers with deeper samples indicates a varying contribution of terrigenous OM and a strong degradation of marine OM components in favor of leaving the long-chained compounds that increase a terrigenous signature of the sediments. The marine component is higher than analysis of deeper biomarkers tends to indicate. Polyaromatic hydrocarbons (PAH) are low in concentration, and no human pollution effects were detected. Perylene data suggest active diagenesis down the sediment core.