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At Cima Uzza, the tonalitic Adamello batholith and volumetrically minor gabbroic stocks and dikes were emplaced into a thick sequence of silica-poor dolostone. Stable isotopic data from dolomite in dolomitic marble in the contact aureole [[delta]18O = 29·7 ± 1·3%° (1[sgr]), [delta]13C = 2·2 ± 1·3%°] and from equivalent dolostone outside the aureole ([delta]18O = 28·8 ± 1·1%°, [delta]13C = 2·5 ± 0·2%°) are indistinguishable. These high and uniform [delta]18O values in the dominant lithology suggest metamorphism in a closed system, as does a closed-system reaction model that is consistent with observed isograd development. Localized fluid infiltration is reflected by low [delta]18O (13·2-18·5%°) and [delta]13C (-2·6 to -6·7%°) calcite values in siliceous marble xenoliths entrained in small gabbroic stocks at the tonalite margin. Such siliceous marble probably formed by Si and Al metasomatism of dolomitic marble during infiltration of magmatic fluids because no equivalent lithology occurs outside the aureole. Brucite marble, which occurs in xenoliths and as reaction rims around mafic dikes, displays a wide range of [delta]18O and [delta]13C values which are generally intermediate between those for siliceous marble and dolomitic marble. This range of isotopic values in brucite marble is consistent with a hydrothermal formation from a silica-poor dolostone protolith. In contrast, high [delta]18O values from centimeter-scale calc-silicate nodules and layers, which are irregularly distributed in the dolomitic contact aureole, indicate a sedimentary origin for such rocks. Hydrothermal alteration of dolomitic marble at Cima Uzza is limited to small areas near gabbroic stocks and dikes, whereas negligible country rock alteration is associated with the larger tonalite. The limited infiltration of magmatic fluids possibly reflects a low volatile content in the tonalitic magma. In addition, low permeability in the thick sequence of dolomitic marble could explain the small amount of fluid flow relative to other carbonate contact aureoles. [ABSTRACT FROM PUBLISHER]

Symbioses involving animals and chemoautotrophic bacteria form the foundation of entire ecosystems at deep-sea hydrothermal vents and cold seeps, but have so far not been reported in terrestrial or freshwater environments. A rare example of a terrestrial ecosystem sustained by chemoautotrophy is found within the sulfide-rich Frasassi limestone cave complex of central Italy. In this study, we report the discovery of abundant filamentous bacteria on the exoskeleton of Niphargus ictus, a macroinvertebrate endemic to Frasassi. Using 16S rDNA sequencing and fluorescence in situ hybridization (FISH), we show that N. ictus throughout the large cave complex are colonized by a single phylotype of bacteria in the sulfur-oxidizing clade Thiothrix. The epibiont phylotype is distinct from Thiothrix phylotypes that form conspicuous biofilms in the cave streams and pools inhabited by N. ictus. Using a combination of 13C labeling, FISH, and secondary ion mass spectrometry (SIMS), we show that the epibiotic Thiothrix are autotrophic, establishing the first known example of a non-marine chemoautotroph-animal symbiosis. Conditions supporting chemoautotrophy, and the N. ictus-Thiothrix association, likely commenced in the Frasassi cave complex between 350,000 and 1 million years ago. Therefore, the N. ictus-Thiothrix symbiosis is probably significantly younger than marine chemoautotrophic symbioses, many of which have been evolving for tens to hundreds of million years.