The magmatic-hydrothermal evolution of porphyry-style mineralization in the shallow crust that is linked to magmatic processes at depth has been extensively studied using bulksample isotopic analysis combined with relative timing constraints. However, a lack of evaluation of the fluid evolution process against an absolute time frame limits further understanding of the ore-forming process. Here,...

Phase-separation and -segregation (boiling/distillation of subseafloor hydrothermal fluids) represent the primary mechanisms causing intra-field variations in vent fluid compositions. To determine whether this geochemical process affects the formation of microbial communities, we examined the microbial communities at three different vent sites located within a few tens meters of one another. In...

We describe how seafloor heat flow is determined, review current understanding of advective heat loss from oceanic lithosphere, and present results from three field areas to illustrate how heat flow measurements are used (along with complementary data) to resolve fluid flow rates and patterns. Conductive heat flow through much of the seafloor is lower than predicted by lithospheric cooling mode...

Variations in the Mg, Ca, Sr, and SO4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). We present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87Sr/86Sr of op...

Petrological, geochemical and Nd-isotopic analyses have been carried out on rock samples from the Rainbow vent field to assess the evolution of the hydrothermal system. The Rainbow vent field is an ultramafic-hosted hydrothermal system located on the Mid-Atlantic Ridge, characterized by vigorous high-temperature venting (~365ºC) and unique chemical composition of fluids: high chlorinity, low pH...

Introduction: On Mars, the geomorphology of numerous surface features has been attributed to the interaction of magmatic and impact heat sources with an H 2 O-rich Martian crust/megaregolith [1-3]. In addition , geochemical analyses of soil at the Pathfinder and Viking landing sites indicate high concentrations of SO 3 and Cl [4-6], consistent with interaction between a basaltic protolith and f...

Porphyry deposits are copper-rich orebodies formed by precipitation of metal sulphides from hydrothermal fluids released from magmatic intrusions that cooled at depth within the Earth's crust. Finding new porphyry deposits is essential because they are our largest source of copper and they also contain other strategic metals including gold and molybdenum. However, the discovery of giant porphyr...

A knowledge of the stability of iron complexes in hydrothermal solutions is important for quantitative interpretation of the chemical behaviour of iron in hydrothermal systems. It is generally accepted that iron is predominantly transported as Fe(II) species in reduced acid fluids whereas Fe(III) hydroxy complexes become also important in reduced alkaline solutions. Previous studies on iron tra...

Subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle (i.e., serpentinite). However, geosphere-biosphere interactions in serpentinite-hosted subseafloor mixing zones remain poorly constrained. Here we examine fossil microbial communities and fluid mixing pr...