Geologica Acta

Comparative study of iron and trace element mobilization during Fe-oxide bioreduction in mine tailings: a case study of Ensenada Chapaco (Chile) and Portman Bay (Spain)

Thu, 27 Feb 2025 00:00:00 +0000

elements (e.g. Ti, Ni, Cd, Pb), leading to contamination of the marine environment. Sea-Tailings Disposal (STD) along the northern coast of Chile (Ensenada Chapaco) and along the eastern coast of Spain (Portman Bay) results in an adverse impact on the environment. This paper focuses on bioreduction under marine conditions. To this end, two column experiments were carried out with samples from Portman Bay and Ensenada Chapaco. Lactate (i.e. organic matter source) was supplied during the experiments. The results obtained are compared with those from batch experiments performed under similar conditions.
In the column filled with Portman Bay tailings, the high content of magnetite (15wt%) in contact with water gives rise to a large magnetite surface area and abundant Fe(III), which results in a high release of Fe(II) and Trace Elements (TE). Since Fe(II) adsorbs onto the magnetite surface reducing the availability of Fe(III), the magnetite bioreduction and the consequent TE release decrease after 2000h. By contrast, the magnetite bioreduction lasts longer (3000h) in the column with Ensenada Chapaco tailings. This is because a lower magnetite content in the tailings (1wt%) provides a smaller reactive surface area yielding less Fe(III). Consequently, the concentrations of Fe(II) and TE in the output solutions are lower, which slows down the Fe(II) adsorption onto magnetite. This results in a longer magnetite bioreduction. Bioreduction is regulated by the availability of Fe(III) in both columns.
It is inferred that the bioreduction rate diminishes as a function of time and increases as a function of soluble Fe(II) concentration. Moreover, the concentrations of TE released from the two bioreduced tailings exceed the elemental concentrations under marine conditions.

The Chicxulub crater drilling program – continuous coring, well logging and core analyses reviewed

Thu, 20 Feb 2025 00:00:00 +0000

Continuous core recovery, core scanning and logging are used for borehole characterization and petrophysical analyses in the Chicxulub drilling projects. The crater formed by an asteroid impact on the Yucatan platform ~66Ma ago, marking the Cretaceous/Paleogene (K/Pg) boundary. The K/Pg boundary clay layer, characterized by the Ir and platinum group element anomaly, has been studied worldwide. The crater has a ~200km rim diameter and is covered by up to ~1km of carbonate sediments, with studies based on geophysical surveys, drilling and ejecta deposits. The Yaxcopoil-1 borehole, drilled in the southern crater terrace zone sampled the post-impact carbonates, impact breccias and target Cretaceous carbonates. The M0077A borehole drilled in the marine sector sampled the peak ring succession, with the post-impact carbonates, impact breccias, melt and basement. The Yaxcopoil-1 and M0077A boreholes were continuously cored from about 400m to 1511 and 1335m, respectively and sampled distinct crater structures. Studies provide constraints on the crater formation, crustal deformation, lateral/vertical displacement, ejecta emplacement and crater collapse. Impact breccias are heterogeneous materials, with clasts of melt, carbonates and basement in carbonate-rich and melt-rich matrix. The lower breccias were emplaced by high-temperature basal surges, followed by collapse of the impact plume and lateral curtains. The upper breccias are reworked deposits of the post-collapse stage. The crater formed a depositional basin, filled with sediments that preserve records of sea level and sediment transport across the platform. Core analyses and scans provide constraints on the structure, stratigraphy, textures, mineralogy, deformation and hydrothermal alteration. Studies show the usefulness of continuous coring and core analyses to constrain the crater formation, impact deformation, ejecta and impact dynamics.

Early Pliocene paleoenvironmental and paleoclimatic reconstruction of shallow lacustrine depositional systems in the Baklan Basin, SW Anatolia, Turkey

Hülya Alçiçek, Johannes M. Bouchal, Mehmet Cihat Alçiçek — Tue, 11 Mar 2025 00:00:00 +0000

A multiproxy study of the Lower Pliocene (Zanclean) shallow lacustrine succession in the southwestern margin of the Baklan Basin (SW Anatolia, Turkey) provides new insights into the paleoclimatic, paleohydrologic, and paleovegetation evolution of an extensional basin located at the top of the western Taurides mountain range in the southeastern Mediterranean region. Detailed petrographic, sedimentological, palynological and stable isotope analyses on Mg-rich carbonates were carried out on the dolomitic succession in the Sapaca locality in the basin, indicating a vegetated, quiet to slow-moving, low-gradient, perennial, alkaline shallow lake environment rich under warm and arid climate conditions. The stable isotopic analysis of the dolomitic carbonates exhibits a narrow range of values (-1.31<δ¹⁸O<+5.82‰ and -7.10<δ¹³C<-2.10‰) and the δ¹⁸O–δ¹³C correlation (r=0.70) indicates a hydrologically closed lake. Two types of dolomite are identified in the studied section. Type-1 crystals formed mainly as a result of primary precipitation of dolomite in the shallow lake, whereas type-2 crystals probably indicate microbially controlled dolomite precipitation. The palynological record from Sapaca reveals that the Early Pliocene paleoenvironment was dominated by steppe and open vegetation with some isolated shrubs. Similar paleoclimatic and paleovegetational conditions are observed in other Anatolian basins and the southern Mediterranean region. Therefore, the results of this study demonstrate that the shallow lacustrine system of the Baklan Basin serves as a good analogue for understanding Early Pliocene warmth and aridity in this region.

An Integrated Remote Sensing, Petrographic, and Mineralogical Techniques for Mapping of Marble Deposits in the Vicinity of the Ophiolite Sequence in North Pakistan

Muhammad Shahab, Liaqat Ali — Wed, 19 Feb 2025 00:00:00 +0000

Marble, a high-pressure and high-temperature metamorphic rock primarily composed of calcium carbonate (CaCO3) and calcium magnesium carbonate (CaMgCO3), has been utilized extensively by ancient civilizations for various architectural purposes globally. The expansion of marble production during the 19th century facilitated its widespread use, with major quarries emerging in various regions, notably China, India, Italy, and Turkey. Despite its historical significance and economic importance, mapping and identifying marble deposits in remote and inaccessible areas remain challenging.

This study presents an integrated approach utilizing advanced remote sensing techniques for mapping carbonate lithologies in the Northwest Mohmand District, Khyber Pakhtunkhwa, Pakistan. By employing advanced spaceborne thermal emission and reflection radiometry (ASTER) imaging coupled with iterative adaptive reweighted regression (IARR), principal component analysis (PCA), minimum noise fraction (MNF), and spectral angle mapper (SAM) classification techniques, we processed and analysed the ASTER images using the Environment for Visualizing Images (ENVI) software. Subsequently, geographic information systems (GIS), ArcMap, and ArcScene software were used for spatial analysis and model generation.

Validation of the results was conducted through extensive fieldwork, X-ray diffraction (XRD), and petrographic analysis. The XRD and petrographic data corroborated the findings derived from the classified ASTER imagery, confirming the presence of significant concentrations of dolomite and calcite, which are indicative of carbonate deposits. The integration of these techniques underscores the efficacy of remote sensing as a viable tool for identifying and mapping mineralized zones in remote locations.

The findings of this study have significant implications for Pakistan's marble industry, particularly in Khyber Pakhtunkhwa, Punjab, and Baluchistan, where an estimated 300 million tons of marble reserves exist. Leveraging remote sensing techniques, this research contributes to the delineation of valuable marble resources and facilitates recommendations for targeted exploration activities in the Mohmand area and beyond.

Major-element analysis of the La Alquimia Compañía Anónima rock collection: Establishing a geochemical repository for the systematic classification of Iberian karstic bauxite and kaolin deposits

Wed, 02 Apr 2025 00:00:00 +0000

The La Alquimia Compañía Anónima rock collection comprises a diverse range of rock samples collected across the Iberian Peninsula to identify bauxites suitable for aluminum oxide production. In this study, the major-element compositions of the rock samples were analysed using non-destructive portable X-Ray Fluorescence (XRF). The data were processed through Principal Component Analysis (PCA), calibrated and used to calculate the Index of Laterisation/Index of Bauxitisation (IOL/IOB) and the Chemical Index of Alteration (CIA). The PCA results revealed SiO₂, Al₂O₃ and Fe₂O₃ as the key components explaining most of the rock samples compositional variance. The calibrated data provided the major element compositions, confirming that the rock samples predominantly correspond to karstic bauxites and kaolin deposits. For the karstic bauxite samples, the calculated IOL/IOB values, combined with the SiO₂–Al₂O₃–Fe₂O₃ ternary diagram, facilitated their classification. The samples were categorised into bauxitic types associated with regions of moderate uplift and karst development and near-lateritic types indicative of advanced weathering processes typical of more stable continental terrains under warm and humid climates. Besides, the calculated CIA values and the Al₂O₃–CaO*+Na₂O–K₂O ternary diagram were applied to classify the kaolin deposits. This approach also identified compositional variations among the kaolin rock samples, reflecting differences in their formation. The rock collection serves as a repository for advancing the regional understanding of the formation, distribution and geochemical trends of Iberian karstic bauxite and kaolin deposits. Moreover, these deposits hold significance as potential sources of Al, Li and REE, emphasising the value of the La Alquímia Compañía Anónima collection as a geochemical repository, particularly considering the growing demand for these critical resources.

Latest Barremian - early Aptian chronostratigraphy and sedimentary evolution of the northwestern Maestrat Basin

Sat, 01 Feb 2025 00:00:00 +0000

Some aspects on the age and correlation of the upper Barremian-lower Aptian stratigraphic units of the NW Maestrat Basin were uncertain prior to this study, due to the differing lithostratigraphy of the marginal Oliete subbasin compared to the more depocentral Galve and Morella subbasins. New magnetostratigraphic, ammonite and sedimentological data presented in this study refine the age and sequence stratigraphy of the upper Barremianlower Aptian succession, enabling a direct and precise correlation across these subbasins. Three third-order TR sequences are identified. The lower boundary of Sequence 1 corresponds to a transgressive surface found on top of the continental red beds of the lower Morella Fm. These beds are equivalent in age to the continental succession of the upper Blesa Fm. (Fm. (Oliete subbasin). The boundary between the M1 and M0r magnetozones (latest Barremian) is found above this surface, in the lower part of the Alacón Fm. Sequence 1 includes the lower part of the Alacón Fm., which passes basinwards to the upper Morella and Xert formations. Sequence 2 corresponds to the upper part of the Alacón Fm and basinwards to the Cap de Vinyet and Barra de Morella members of the Forcall Fm. The boundary between the M0r and C34n magnetozones (earliest Aptian) is found towards the lowermost part of Sequence 2. Sequence 3 includes the Josa Fm and its offshore equivalents, the Morella la Vella Mb. and the Villarroya de los Pinares Fm. Additionally, the overall facies distribution in successive depositional stages is reconstructed, describing the lateral transition from marginal protected to open marine areas. The improved chronostratigraphic framework presented here will enable more accurate correlations with other subbasins of the Maestrat Basin, and the reconstructed sedimentary evolution may be useful for the interpretation of other Lower Cretaceous successions of the Tethys.

Paleogene kinematics of the central Catalan Coastal Ranges: temporal constraints from magneto-chronology and provenance analysis in synorogenic deposits in the SE margin of the Ebro Basin (NE Spain)

Sat, 01 Feb 2025 00:00:00 +0000

The precise determination of the tectonic deformation timing such as thrust emplacement has always been a challenge for understanding the evolution of fold-and-thrust belts. In the Catalan Coastal Ranges, this issue has traditionally been addressed through the mapping and the analysis of the syn-tectonic successions preserved in the SE margin of the Ebro Basin. However, the age of the Paleogene contractional structures located towards the hinterland and responsible of the inversion and uplift of the inherited Mesozoic structure remained uncertain due to the lack of preserved syn-kinematic strata in these areas. With the aim of better understand the contractional evolution of the area during the Paleogene, this work presents a tectono-stratigraphic analysis approach that combines structural reconstructions, provenance analysis and magnetostratigraphic dating in well-exposed synorogenic sediments in the central SE margin of the Ebro Basin. The results of the study allow to establish the precise age of the main contractional structures present in the central Catalan Coastal Ranges. The combined analysis has revealed that: i) the inversion of the Montmell-Vallès Faults System started in the Bartonian and continued up to the late Priabonian, and ii) the emplacement of the Gaià-El Camp Thrust and the formation of the Cabra-Carme Anticline took place from early to late Priabonian and was the responsible of the sudden increased of the sedimentation rates. A later decrease of the sedimentation rates during late Priabonian (chron C15n) has been interpreted as the prelude of the end of the Paleogene compressional phase in the area.

The non-marine Lower Cretaceous of El Montsec thrust sheet (South-Central Pyrenees)

Carles Martín-Closas, Iván Lozano-Fernández, Jordi Pérez-Cano, Telm Bover-Arnal — Tue, 25 Mar 2025 00:00:00 +0000

The aim of this study is resolving uncertainties on the lithostratigraphy and chronostratigraphy of the non-marine Lower Cretaceous of El Montsec thrust sheet, which contains the most developed record of such facies in the central Pyrenees (Catalonia, Spain). The materials, traditionally known as “El Montsec Charophyte Limestones”, overlie upper Berriasian marine limestones and belong in fact to two different stratigraphic units, separated by an angular unconformity, which is represented by an irregular karstic surface. The lower unit, newly defined as the Cova dels Lladres Intraclastic Limestone Formation, is composed by metric-scale fining-upward parasequences with black intraclast conglomerates at the base covered by charophyte limestones at the top. This first non-marine unit is attributed to the lower Barremian Eurasian charophyte biozone Atopochara trivolvis triquetra. The upper non-marine unit, (revisited El Montsec Charophyte Limestone), is made of metric-scale fining-upward parasequences of charophyte limestones. Ferruginous marls at the base of the upper unit have yielded charophytes of the Hemiclavator neimongolensis neimongolensis Eurasian charophyte biozone, corresponding to the early–late Barremian boundary. El Montsec Charophyte Limestone Formation transitions laterally to La Pedrera de Rúbies Lithographic Limestones Formation, which includes the two famous fossil Konservat Lagerstätten of La Pedrera de Meià and La Cabroa. In sum, the non-marine Lower Cretaceous succession of El Montsec thrust sheet shows at its base a stratigraphic gap ranging from the upper Berriasian to the early Barremian. Furthermore, the angular unconformity separating the Cova dels Lladres Formation and El Montsec Formation clearly reflects the strong tectonic activity associated with the Barremian Iberian rift, which has been linked with the opening of the Bay of Biscay.