X-ray computed tomography study for drill core of the Drazhnoe orogenic-type gold deposit (Sakha (Yakutia), Russian Federation)

Orogenic gold-quartz deposits have a clear structural control and are accompanied by wallrock metasomatic alteration. However, in detailed modeling of such deposits, there is often a mismatch between the structural plans for high-grade ore zone distribution and metasomatite zones, and the latter are not always associated with faults. This is explained by the evolution of the hydrothermal process and the pulsating nature of the development of the territory. In the early stages of the mineral deposit study, it is very important to reliably determine the distribution of ore zones, since the correct targeting of the drilling program and the economic deposit assessment depend on it. The problem can be solved using the method of X-ray computed tomography (СТ) in the core study. This paper presents the methodology of studying fullsize core samples of gold deposits by using CT. A core sample characterizing the central part of ore body of Drazhnoye deposit (Tarynskoye ore field, Republic of Sakha (Yakutia)) was used as the study material. The sample studied was scanned by a SIEMENS Somatom Perspective tomograph at two energies (80 and 130 keV). As a result, a detailed three-dimensional stereological model of the core was obtained, which made it possible not only to study the distribution of ore minerals in the volume of the entire sample, but also to identify vein bodies of different ages, as well as to study their morphology and trace the distribution patterns of ore mineralization in them. Based on the study results, we can offer a preliminary interpretation of ore mineralization and vein formation sequence.

Progressive veining during peridotite carbonation: insights from listvenites in Hole BT1B, Samail ophiolite (Oman)

The reaction of serpentinized peridotites with CO2-bearing fluids to listvenite (quartz-carbonate rocks) requires massive fluid flux and significant permeability despite increase in solid volume. Listvenite and serpentinite samples from Hole BT1B of the Oman Drilling Project help to understand mechanisms and feedbacks during vein formation in this process. Samples analyzed in this study contain abundant magnesite veins in closely spaced, parallel sets and younger quartz-rich veins. Cross-cutting relationships suggest that antitaxial, zoned carbonate veins with elongated grains growing from a median zone towards the wall rock are among the earliest structures to form during carbonation of serpentinite. Their bisymmetric chemical zoning of variable Ca and Fe contents, a systematic distribution of SiO2 and Fe-oxide inclusions in these zones, and cross-cutting relations with Fe-oxides and Cr-spinel indicate that they record progress of reaction fronts during replacement of serpentine by carbonate in addition to dilatant vein growth. Euhedral terminations and growth textures of carbonate vein fill together with local dolomite precipitation and voids along the vein – wall rock interface suggest that these antitaxial veins acted as preferred fluid pathways allowing infiltration of CO2-rich fluids necessary for carbonation to progress. Fluid flow was probably further enabled by external tectonic stress, as indicated by closely spaced sets of subparallel carbonate veins. Despite widespread subsequent quartz mineralization in the rock matrix and veins, which most likely caused a reduction in the permeability network, carbonation proceeded to completion in listvenite horizons.

Features of morphometric parameters of vessels in the human portal venous system identified by multislice computed tomography

The aim of this study was to identify the morphometric features of the human portal venous system by means of multislice computed tomography (MSCT).Materials and methods. A contrast X-ray study of the portal vein was carried out in 53 men who were treated in the surgical departments of the Krasnoyarsk Regional Hospital No. 1. The average age of the patients was 54.9 ± 1.7 years (36–71 years). Measurements were performed on 3D models of the vascular bed in the portal venous system (GE Advantage Workstation and Siemens singo.via workstations). Branching patterns, length, diameter, angle of the portal vein formation relative to the midline of the human body, and angles of formation of the vessels forming the portal vein in the frontal plane were evaluated.Results. Variations in the morphometric parameters of the intrahepatic vessels of the portal vein are obvious, although the branching patterns are not diverse and are reduced to one type – the magistral pattern (according to V.N. Shevkunenko). The veins that form the portal vein are represented by three systems, each of which has a stem and tributaries that differ in branching patterns and other morphological characteristics.Conclusion. The findings of the study made it possible to supplement the scientific materials regarding branching patterns and morphological characteristics of the portal vein and its tributaries as well as to use the morphometric characteristics of the superior and inferior mesenteric and splenic veins to resolve the issues of surgical intervention on the abdominal organs.

Age, material source, and formation mechanism of bedding-parallel calcite beef veins: Case from the mature Eocene lacustrine shales in the Biyang Sag, Nanxiang Basin, China

The mechanisms leading to the formation of bedding-parallel calcite beef veins have been widely debated, with discussions centered on timing or burial depth of vein generation, source of the vein material, driving forces for vein initiation and widening, and growth direction and mechanism. To address these issues, a comprehensive study of drill core samples containing beef veins in the mature Eocene lacustrine Hetaoyuan Formation in the Biyang Sag, Nanxiang Basin, China was undertaken through a combination of microstructural observation, isotopic geochronological, geochemical, and fluid inclusion analyses, as well as basin modeling. X-ray diffraction and total organic carbon content analyses indicate that most of the beef veins accumulated in calcite-rich laminated shales with high organic matter contents. These beef veins yielded an absolute laser ablation−multi-collector−inductively coupled plasma−mass spectrometry U-Pb age of ca. 41.02 ± 0.44 Ma, which corresponds to a burial depth of 500−800 m. Such a shallow burial depth suggests that the full compaction and consolidation of sediments would not yet have been achieved, which is compatible with the following observations: (1) plastic deformation of shale laminae adjacent to the veins, and (2) a beef vein formation temperature of ∼59 °C derived from fluid-inclusion microthermometry. The radio-isotopic age of the beef veins is ∼1−3 m.y. younger than the stratigraphic age of the host rock (ca. 43.1 Ma) but earlier than the model-derived timing of oil generation (ca. 35.8 Ma) and tectonic extrusion (ca. 23.0−13.0 Ma). The beef vein formation predated bacterial sulfate reduction, as evidenced by crosscutting relationships with carbonate concretions, pyrite framboids, and apatite pellets. A two-stage formation model for these beef veins is proposed. When burial depth of laminated shales rich in organic matter and calcite reaches the methanogenic zone, overpressure triggered by biogenetic gas generation results in horizontal hydrofracturing, initiating cracks that act as gas expulsion pathways. Once all the generated gas has migrated, the opened fractures close again due to overburden load. The materials fed by pressure solution of host-rock calcite fractions then mobilized into the unhealed horizontal fractures by diffusion. Subsequently, by a force of crystallization, antitaxial, displacive growth of calcite fibers commenced, contemporaneous with fracture dilation, eventually leading to the formation of bedding-parallel beef veins.

A molecular framework for proximal secondary vein branching in the Arabidopsis thaliana embryo

The establishment of a closed vascular network in foliar organs is achieved through the coordinated specification of newly recruited procambial cells, their proliferation and elongation. An important, yet poorly understood component of this process, is secondary vein branching; a mechanism employed in Arabidopsis thaliana cotyledons to extend vascular tissues throughout the organ surface by secondary vein formation. To investigate the underlying molecular mechanism in vein branching, we analyzed at a single-cell level the discontinuous vein network of cotyledon vascular pattern 2 (cvp2) cvp2-like 1 (cvl1). Utilizing live-cell imaging and genetic approaches we uncovered two distinct branching mechanisms during embryogenesis. Similar to wild type, distal veins in cvp2 cvl1 embryos emerged from the bifurcation of cell files contained in the midvein. However, the branching events giving rise to proximal veins are absent in this mutant. Restoration of proximal branching in cvp2 cvl1 cotyledons could be achieved by increasing OCTOPUS dosage as well as by silencing of RECEPTOR LIKE PROTEIN KINASE 2 (RPK2) expression. The RPK2-mediated restriction of proximal branching is auxin and CLE-independent. Our work defines a genetic network conferring plasticity to Arabidopsis embryos to adapt the spatial configuration of vascular tissues to organ growth.

Hypozonal gold mineralisation in shear zone hosted deposits driven by fault valve action and fluid mixing: the Nalunaq deposit, Greenland

The Nalunaq deposit, Greenland, is a hypozonal, shear zone-hosted, Au deposit. The shear zone has previously been interpreted to have undergone 4 stages of deformation, accompanied by fluid flow,and vein formation. Coupled with previous trapping T estimates, fluid inclusion data are consistent with trapping of fluids with salinities between 28-45 wt. % NaCl eq., from 300-475°C during D2 and D3, with pressure varying between ∼800 and 100Mpa. The range reflects pressure cycling during seismic slip related depressurisation events. D4 fluids were lower salinity and trapped from 200-300°C, at ∼50-200Mpa during late stage normal faulting. The variation in major element chemistry is consistent with ingress of hypersaline, granitoid equilibrated fluids into the shear zone system and mixing with fluids that had reacted with the host metamorphic rocks. D4 stage fluids represent ingress of meteoric fluids into the system. Gold contents in inclusion fluids range from ∼300-10mg/kg. These data are consistent with the high P-T solubility of Au as AuHS(H2S)30 complexes, and Au deposition by decompression and cooling. The high salinities also suggest Au transport as chloride complexes may have been possible. Gold distribution was modified by the release of chemically bound or nanoscale Au during sulphide oxidation at the D4 stage.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635812

Control of vein-forming, striped gene expression by auxin signaling

Background Activation of gene expression in striped domains is a key building block of biological patterning, from the recursive formation of veins in plant leaves to that of ribs and vertebrae in our bodies. In animals, gene expression is activated in striped domains by the differential affinity of broadly expressed transcription factors for their target genes and the combinatorial interaction between such target genes. In plants, how gene expression is activated in striped domains is instead unknown. We address this question for the broadly expressed MONOPTEROS (MP) transcription factor and its target gene ARABIDOPSIS THALIANA HOMEOBOX FACTOR8 (ATHB8). Results We find that ATHB8 promotes vein formation and that such vein-forming function depends on both levels of ATHB8 expression and width of ATHB8 expression domains. We further find that ATHB8 expression is activated in striped domains by a combination of (1) activation of ATHB8 expression through binding of peak levels of MP to a low-affinity MP-binding site in the ATHB8 promoter and (2) repression of ATHB8 expression by MP target genes of the AUXIN/INDOLE-3-ACETIC-ACID-INDUCIBLE family. Conclusions Our findings suggest that a common regulatory logic controls activation of gene expression in striped domains in both plants and animals despite the independent evolution of their multicellularity.