Accurate determination of structural H2O in rocks using LIBS coupled with machine learning algorithms extensively exploring the characteristics of the Hα line

The application of laser-induced breakdown spectroscopy (LIBS) in elemental analysis and property assessment of geological materials has been demonstrated of great importance and effectiveness. The importance of the application becomes...

Early Earth zircons formed in residual granitic melts produced by tonalite differentiation

The oldest geological materials on Earth are Hadean (>4 Ga) detrital zircon grains. Their chemistry and apparently low Ti-in-zircon temperatures (≤700 °C) are considered to be inconsistent with crystallization in a magma of the tonalite-trondhjemite-granodiorite (TTG) suite, although these are the dominant Archean (4.0–2.5 Ga) silicic rocks. Using a new data set of trace element contents in zircons from Paleoarchean Barberton TTGs (South Africa) and thermodynamic modeling, we show that these zircons have crystallized at near-solidus conditions from a compositionally uniform granitic melt. This melt is residual from the crystallization of a less evolved (tonalitic) parent and thereby shows major and trace element compositions different from bulk TTG rocks. A global compilation reveals that most Hadean detrital and Archean TTG-hosted grains share a peculiar zircon trace element signature that is distinct from the chemical trends defined by Phanerozoic zircons. Our model shows that the low Ti contents of early Earth zircons reflect crystallization at higher temperatures (720–800 °C) than initially inferred due to lower modeled TiO2 activity in the melt relative to previous estimates. We therefore propose that near-solidus zircon crystallization from a chemically evolved melt in a TTG-like magmatic environment was the dominant zircon-forming process on the early Earth.

EXPERIENCE IN APPLYING EXPERT ANALYSIS AND RANK CORRELATION DURING GEOLOGICAL AND FORECASTING WORK ON HYDROCARBONS

Problem Statement and Purpose. The diverse and extensive geological materials and geophysical data used in forecasting and prospecting operations for oil and gas exploration within the Black Sea’s northwestern shelf are usually interpreted in a complex manner. This complexity, however, is often spontaneous and fragmentary, with no new theoretical concepts taken into account. For example, the theory of global fluidogenesis represents an alternative hypothesis to the organogenic-sedimentary formation of hydrocarbon deposits but is commonly not considered. The authors of this article believe that the complexity should be replaced by a method of directed rank interpretation of geological information, in which ranking distinguishes the maximum information on one of the sections of geological work with regard to its completeness and consistency. The purpose of this study is to apply expert analysis and rank correlation of obtained information to geological and forecasting research on hydrocarbons. To achieve this goal, two basic principles, rank and direction, are considered. The data include seismic, tectonic-geodynamic, lithological, geochemical, mineralogical, and meiobenthic characteristics of the sea bottom scaled according to their sensitivity to the independent variable, i. e., hydrocarbons. Study area, material, and methods. The Pradneprovskaya area has been chosen for analysis. It is a promising location for oil and gas exploration in the shallow part of the inner northwestern shelf of the Black Sea. Geologically, this is the area of junction for the South Ukrainian monocline with the system of blocks included in the Predobrudzha-Crimean riftogenic trough. The area was studied by geophysical, geochemical (hydrocarbon gases, liquid hydrocarbons), mineralogical (X‑ray diffraction of clay minerals, thermobarogeochemistry of inclusions in minerals), and paleontological (foraminifera, nematodes, ostracods) methods, along with the drilling of a deep (2352 m) parametric well (Pradneprovskaya‑2). Results. It is shown that expert analysis of the diverse information within the framework of selected tasks, which are poorly formalized into a single system, provides the basis for an effective method of comparing information databases formed on different principles. This analysis is founded on the principle of directed (vector) ranking, where each rank narrows the search area and becomes more sensitive to the hydrocarbon deposit. The article gives an example of how this method can be used for a specific objective in its entirety, namely: (a) selection of information ranks (parameters), (b) selection of experts, (c) calculation of the rank matrix, (d) determination of hierarchical dependencies of ranks, (e) verification of the matrix, and (e) calculation of the concordance coefficient. The obtained results indicate that the proposed method of expert analysis with rank correlation under modern conditions using diverse geological materials that are not formalized into a single database, provides high reliability in the comprehensive interpretation of data. The method will help optimize geological and forecasting research on hydrocarbons within the Black Sea shelf.

Aquifer Parameters Estimation from Natural Groundwater Level Fluctuations at the Mexican Wine-Producing Region Guadalupe Valley, BC

Determining hydrogeological properties of the rock materials that constitute an aquifer through stress tests or laboratory tests presents inherent complications. An alternative tool that has significant advantages is the study of the groundwater-level response as a result of the pore-pressure variation caused by the internal structure deformation of the aquifer induced by barometric pressure and solid Earth tide. The purpose of this study was to estimate the values of the physical/hydraulic properties of the geological materials that constitute the Guadalupe Valley Aquifer based on the analysis of the groundwater-level response to barometric pressure and solid Earth tide. Representative values of specific storage (1.27 × 10−6 to 2.78 × 10−6 m−1), porosity (14–34%), storage coefficient (3.10 × 10−5 to 10.45 × 10−5), transmissivity (6.67 × 10−7 to 1.29 × 10−4 m2∙s−1), and hydraulic conductivity (2.30 × 10−3 to 2.97 × 10−1 m∙d−1) were estimated. The values obtained are consistent with the type of geological materials identified in the vicinity of the analyzed wells and values reported in previous studies. This analysis represents helpful information that can be considered a framework to design and assess management strategies for groundwater resources in the overexploited Guadalupe Valley Aquifer.

Geological Materials in Late Antique Archaeology: The Lithic Lectern Throne of the Christian Syrian Churches

The geological materials used in early Christian Syrian churches involve a lithic furnishing element: the lectern throne of the Syriac bema, a stone device used as a support for the holy books. Some inscriptions found in Syria suggest an interpretation for this artifact, located in the middle of the Syriac bema hemicycle, fronting the altar zone. These elements were made of basalt or limestone, depending on the geographical–geological context of the building. In this work, an unedited classification of the main typologies of thrones is proposed with a collatio between geo-archaeological data, epigraphic texts, mosaic inscriptions, literary sources, and findings. The role of this uncommon piece of furniture, uncertain up to now, is explained with a new interpretation coming from archaeological–architectural data combined with ancient sources. The study thus locates this architectonical sculpture in the building stratigraphy and also describes decorations from the lecterns, thus contributing to chronology analysis of published and unedited Syrian sites.