Fluid migration recorded by fluid inclusions in crack-sealed quartz veins and sandstone host rock; Cameros Basin, Spain

The role of deep hydrothermal fluid circulation through fractures and their impact on the sandstone host rock is studied in an extensional sedimentary basin (Cameros Basin, Spain) affected by a post-extensional hydrothermal metamorphism. The quartzarenites of the Urbión Group constituted a hydrocarbon carrier affected by very low to low-grade hydrothermal metamorphism during Late Albian to Coniacian. This process generated abundant quartz veins and transformed the quartzarenites into quartzites. This study compares the microthermometry of the fluid inclusion asemblages (FIAs) in the veins and in the quartz grain overgrowths in the quartzites, in order to understand the behavior of the hydrothermal fluids through fractures and their effects in the host rock. Fluid inclusions in the quartz grain overgrowths contain liquid and vapor at room temperature and homogenize to the liquid (Th: 124–265 °C, H2O + NaCl system). Those of quartz veins present both liquid and vapor CO2 and an aqueous liquid phase (room temperature). Final homogenization is to the liquid (Th: 109–282 °C, H2O + NaCl + CO2, mean values of amount-of-substance fractions: 0.92, 0.01, 0.07). Large Th variation within each FIA is common, due to crack and sealing processes and to reequilibration by successive thermal pulses. In contrast, the narrow Th range in each FIA towards the top of the record indicates that these inclusions are probably not reequilibrated. Two growing stages are recognized under SEM-CL in the quartz grain overgrowths, one diagenetic and another hydrothermal, the later with FIAs showing Th similar than the veins. The results can help in the evaluation of the geo-energy resources in sedimentary basins.

Mineral characteristics of metacarbonat in Sa Thay, Kon Tum and potential use for gemstone

Metacarbonates located in Sa Thay, Kon Tum massif are distributed in ultramafic marble assemblage from Kham Duc (NP-e1kđ) complex.The main rock-formingminerals arecalcite and dolomite (40÷85%), olivine (5÷20%), pyroxene (5÷15%), and serpentine (5÷25%). Accessory minerals aretalc and epidote. Chemical composition of pyroxene in metacarbonate was determined by EPMA method: the composition of pyroxene is diopsite (Wo49.5 En50.1Fs0.4 to Wo50.8En48.9Fs0.2). The rim of pyroxene grains generally have higher wollastonite than core(49.9÷50.8%).Metacarbonates originated from metamorphic sources with three main stages: regional metamorphism, superimposed metamorphismand hydrothermal metamorphism stages. With each stage, they have different color characteristicsto create a variety of color. Metacarbonateshave quality characteristicsofcolor, durability, pattern, diversity, and low radioactivity. These make the metacarbonates suitable for gemstone applications.

Fracture network analysis for carbon mineralization in basalts of the Oligocene Jizan volcanics, Saudi Arabia

<p>This study aims to characterize fracture permeability in altered Oligocene-Early Miocene basalts of the Jizan Group, which accumulated in half grabens during the continental rift stage of Red Sea evolution. Unlike fresh basalts, the Jizan Group was affected by low temperature hydrothermal metamorphism, which plugged the original matrix porosity in vesicles, breccias, and interflow layers with alteration minerals. On the other hand, the basalts are pervasively shattered by open closely spaced fractures in several directions. Characterization of these fractures is essential to reducing the fracture permeability uncertainty for mineral carbonation by the dissolved CO2 process such as Carbfix.<br>Conventional measurements of fracture orientations and densities were initially taken at outcrops of the Jizan Group to characterize the fracture network. Photogrammetry of drone images covering larger areas were then used to create 3D models of the outcrops using Agisoft Metashape, which were analyzed for fracture geometries using Cloud Compare. The automated analysis of fracture orientations and densities compared well with conventional manual measurements. This gives confidence in semi-automated dronebased fracture characterization techniques in 3D, which are faster and less labor intensive, especially for characterization of large and difficult to reach outcrops.<br>Our fracture characterization will be used to construct 3D fracture permeability models of the Jizan Group for combined physical and chemical simulation of injection of dissolved CO2 from industrial sources into basalts. This will provide essential parameters to mitigate geological risks and to determine depth, spacing, and injection rates in CO2 disposal wells.</p>

Connemara Marble, Co. Galway, Ireland: a Global Heritage Stone Resource proposal

Connemara Marble, a well-known distinctive decorative stone from the west of Ireland, is herein proposed as a Global Heritage Stone Resource. Connemara Marble is a sillimanite-grade ophicarbonate, dominated by dolomite and calcite with varying proportions of serpentine, diopside, forsterite, tremolite clinochlore and phlogopite. The marble displays intricate corrugated layers that range in colour from white through sepias to various shades of green. These features impart unique characteristics that set the marble apart from other ornamental stones. Characteristics reflect amphibolite-grade metamorphism of an impure siliceous dolomitic limestone during the Grampian orogeny (475–463 Ma). Olivine, diopside, tremolite along with calcite and dolomite were formed during the peak of metamorphism which was followed by a later pervasive hydrothermal metamorphism that led to the extensive growth of serpentine after olivine and diopside. It has been used since Neolithic times, but has been quarried and fashioned in Connemara since the eighteenth century, and widely utilized in buildings in Ireland and the UK, for cladding, banisters, columns and church fittings. Later in the late nineteenth and early twentieth centuries it was exported in large quantities to the USA for use in civic and educational buildings. Its many uses as an ornamental stone in the interiors of buildings and in Irish jewellery commands worldwide acclaim.