Thin Section Samples Research Articles

Supergene formation of sulfur-rich, tochilinite-bearing serpentinites in the Oman ophiolite

Mass transfer processes between fluids and ultramafic rocks produce subsurface environments encompassing a wide range of redox conditions. A notable locality where an extensive range of redox conditions is observed in one location is Hole BA1B, a ∼ 400 m borehole drilled by the Oman Drilling Project. A sulfur-enriched serpentinite zone, containing up to 0.6 wt% S, occurs between shallow oxidized serpentinites (<30 m) and deep partially serpentinized harzburgite (>150 m). All three alteration zones are predominantly composed of serpentine. However, microanalysis of samples from the sulfur-enriched zone shows that mesh textures after olivine are composed of serpentine, brucite, and tochilinite mixtures, yielding optically black thin-section samples that characterize this sulfidic zone. It is proposed that sulfur accumulates in this zone via a process similar to those found in supergene ore deposits. Reaction-path models show that at shallow conditions open to atmospheric input, sulfur is mobilized via oxidative weathering of serpentinized dunite and harzburgite. Sulfate-bearing fluids percolate deeper and react with host rocks in a system closed to atmospheric input. As fluids become more reduced, dissolved sulfate is precipitated as sulfide minerals yielding rocks with ∼0.4 wt% S, like those observed in Hole BA1B. Despite enrichment of S in the sulfidic zone in Hole BA1B, Ni and Co contents are uniform throughout all three layers in the borehole. This is consistent with model results which show that Ni (and, by analogy, Co) is less mobile than S, and can be hosted in serpentine and NiFe alloys in addition to sulfides. The sulfur enrichment process may occur abiotically. However, sulfide enrichment via microbial reduction of sulfate and other sulfur species can also facilitate the formation of the sulfidic zone. Bioenergetic calculations show that abundant energy is available for sulfur reducing microbes, consistent with previous work demonstrating the presence of active, sulfate-reducing microorganisms in Hole BA1B and other nearby boreholes. This suggests that the observed sulfur enrichment is an ongoing process. Overall, this work shows that variable redox conditions are attained as fluids percolate and react with serpentinized ultramafic rocks at variable extents of interaction between aquifer fluids, host ultramafic rocks, and the atmosphere.

IMAGE-BASED YOLOV4 ARCHITECTURE FOR DETECTING MINERAL IN SEDIMENTARY ROCKS THIN SECTION

Thin section analysis of sedimentary rocks is the basis for identifying minerals and textures. In general, quantitative analysis of thin sections of rock often requires many hours of work when done manually. In today's era, mineralogical interpretation and percentage calculations must be carried out automatically using more practical applications. The research method begins with the identification of 44 thin section samples in parallel plane polarized (PPL) and crossed polarized (XPL) conditions with thin section analysis then mineralogy detection is carried out using a computational approach, namely the use of image-based Deep Learning YoloV4 architecture with 2D RGB image objects from the thin section of sedimentary rock. The results of this study show the best values of Average Precision in Quartz, Feldspar, and lithic are 39.21% in the XPL model, 26.53% in the XPL model, and 15.75% in combined mode, according to the training and testing of YoloV4 Models for the identification of rock minerals in thin sections. Based on the complexity of the mineral types, the granularity of the detection, and the specific geological objectives, establishing a meaningful benchmark or baseline for comparison is always challenging. Additionally, consider discussing the trade-offs between precision and recall, as a higher precision may be more critical in some geological applications. It is expected that the application of this research can produce practical, fast and accurate interpretation of the determination of minerals in sedimentary rocks from all thin-section images of rocks and thus provide a complete understanding of geological views automatically.

Biostratigraphy of the Upper Cretaceous Gurpi Formation: Enhancing correlation potential by identification of abundance events of planktonic foraminifera as auxiliary indicators

The Upper Cretaceous Gurpi Formation represents a pelagic interval composed of shale and marly limestone rich in planktonic foraminifera. This study focuses on the analysis of planktonic foraminifera from the Gurpi Formation in the Zard-Shehneh Anticline section in southwestern Iran. The formation is of significant importance in parts of the Zagros foreland basin, as it acts as both a cap rock and a source rock. The presence of the Cretaceous/Paleogene (K/Pg) boundary at the upper boundary of this formation further emphasizes the significance of studying it. Therefore, the study of its biozonation and bioevents is crucial. Through the recovery of planktonic foraminifera from 125 samples in thin sections and washed residues, 30 genera, 88 species, and 10 biozones were identified for the Gurpi Formation, as well as 7 genera, 12 species, and one biozone for the base of the overlying Pabdeh Formation. In addition, high accuracy was achieved in the placement of bioevents, including: 1) the occurrence of Globotruncana linneiana at the base of the Gurpi Formation, indicating the Santonian age; 2) the highest occurrences of Dicarinella asymetrica and most species of marginotruncanids, marking the Santonian/Campanian boundary; 3) the earlier occurrence of Globotruncana aegyptiaca; 4) the occurrence of the Campanian/Maastrichtian boundary in the lower part of Gansserina gansseri Zone; 5) the occurrences of five abundance events including: V. eggeri in the upper half of the Dicarinella asymetrica Zone, benthic foraminifera in the middle to upper half of the Radotruncana calcarata Zone, G. linneiana, G. lapparenti, and G. esnehensis in the lower part of Globotruncana falsostuarti Zone, G. esnehensis in the upper part of Globotruncana falsostuarti Zone, and G. gansseri at the end of the Pseudoguembelina hariaensis Zone; and 6) the disappearance of most keeled planktonic foraminifera species during the late Maastrichtian, starting from the middle parts of the Abathomphalus mayaroensis Zone. In this study, the K/Pg boundary, which is considered the upper boundary of the Gurpi Formation, exhibits unconformity and condensation. The high-resolution biozonation and bioevents framework not only allows for accurate dating of the Gurpi Formation in the Zard-Shehneh section, but also enhances the ability to precisely correlate sedimentary sequences and paleoenvironmental intervals at regional or global scales in future studies.

A machine learning application for the automatic recognition of planktonic foraminifera in thin sections

The automated recognition of fossil planktonic foraminifera in thin section (TS) samples can bring benefit through reduction of time, costs, and human effort for biostratigraphic analyses. In this work we present the outcomes of an Eni internal Research and Development project aimed at evaluating the feasibility of automated recognition of microfossils by means of computer vision. We trained two Deep-Learning (DL) models to first identify fossil candidates within TS samples and subsequently classify selected taxa among 66 registered Oligocene-Miocene planktonic foraminifera species. In the step of fossil detection, we achieved a mean average precision of 81.4% in extracting bounding boxes containing fossils from raw TS photomicrographs. In the subsequent fossil classification step, we obtained a top-1 accuracy of 70% (i.e., in approximately 70% of cases, the label assigned by the biostratigraphers coincided with the model best guess) and a top-3 accuracy of 88% (i.e., in 88% of cases, it was included within the top-3 species predicted by the model). Given these promising performances, the fossil detection and classification pipeline has been deployed in a web application that indicates fossil-containing bounding boxes and suggests the top-3 most likely species for each sample. Biostratigraphers’ corrections/confirmations are stored to be used for future re-trainings and incrementally improve the performances of the algorithms.

Kelimpahan Foraminifera Bentonik Besar

The aim of this research is to determine the abundance of large benthic foraminifera in the study area. This research method is descriptive quantitative. There were 4 thin section samples used in this research, these samples came from cores at a depth of (36m – 39m). The results of the research showed that from the four incisions, 7 variations of large benthonic foraminifera genera were found, including, Spiroclypeus, Alveolina, Trillina hawchini, Cycloclypeus, Miogypsina, Heterostegina, and Assilina. Analysis of the abundance of large benthic foraminifera was carried out based on identification of the presence of foramnifera in each thin section sample. It is known that the thin section sample with the highest abundance of large benthonic foraminifera was in the code section sample (38m – 39m) with a total abundance of 9 individuals, consisting of 4 different genera of large benthonic foraminifera. In conclusion, the abundance of large benthic foraminifera tends to increase with increasing core depth. Keywords: Large Benthonic Foraminifera, Genus, Abundance, Rajamandala

Deep UV-excited fluorescence microscopy installed with CycleGAN-assisted image translation enhances precise detection of lymph node metastasis towards rapid intraoperative diagnosis

Rapid and precise intraoperative diagnosing systems are required for improving surgical outcomes and patient prognosis. Because of the poor quality and time-intensive process of the prevalent frozen section procedure, various intraoperative diagnostic imaging systems have been explored. Microscopy with ultraviolet surface excitation (MUSE) is an inexpensive, maintenance-free, and rapid imaging technique that yields images like thin-sectioned samples without sectioning. However, pathologists find it nearly impossible to assign diagnostic labels to MUSE images of unfixed specimens; thus, AI for intraoperative diagnosis cannot be trained in a supervised learning manner. In this study, we propose a deep-learning pipeline model for lymph node metastasis detection, in which CycleGAN translate MUSE images of unfixed lymph nodes to formalin-fixed paraffin-embedded (FFPE) sample, and diagnostic prediction is performed using deep convolutional neural network trained on FFPE sample images. Our pipeline yielded an average accuracy of 84.6% when using each of the three deep convolutional neural networks, which is a 18.3% increase over the classification-only model without CycleGAN. The modality translation to FFPE sample images using CycleGAN can be applied to various intraoperative diagnostic imaging systems and eliminate the difficulty for pathologists in labeling new modality images in clinical sites. We anticipate our pipeline to be a starting point for accurate rapid intraoperative diagnostic systems for new imaging modalities, leading to healthcare quality improvement.

Petrology and Mineralogy of Metamorphic Rocks in The Pringsewu District, Lampung Province, Indonesia

The origin of metamorphic rock is greatly influenced by the temperature and pressure changes in every tectonic setting, especially in active subduction margins. One of the wide outcrops of metamorphic rock occurs in the Pringsewu District, Lampung, and it is a part of the Palaeozoic Gunung Kasih Complex. The presence of metamorphic rocks in Pringsewu has raised several questions and debates for some time due to the lack of research and field evidence found in this area, especially, since the origin of metamorphic rock in Lampung has been rarely studied. This research aims to determine the metamorphic rock facies and the tectonic setting underlying the formation of metamorphic rocks in the study area.&#x0D; Petrographic analysis on 19 thin-section samples shows that metamorphic rock in the research area can be divided into two regions i.e., western and eastern regions. The Eastern part is characterized by muscovite-epidote schist and greenschist which consist of quartz, muscovite, actinolite, epidote, and garnet as index minerals. Whereas the western part is characterized by quartzite and biotite-epidote schist that consist of quartz, biotite, and muscovite. Based on the mineral index, metamorphic rock’s protoliths are pelitic rock, mafic rock, and quartz-feldspathic sandstone. The metamorphic rock zonation shows the created temperature is from 280-550oC.&#x0D; The foliation structure such as schistose and porphyroblastic texture in the whole rocks sample indicated that metamorphic rocks are created in medium-grade metamorphism and are characterized by the greenschist facies to epidote-amphibolite facies. The abundance of quartz, k-feldspar, and labradorite minerals show that metamorphic rocks came from the microcontinent which was caused by a collision between the intra-oceanic Woyla plate and West Sumatra microcontinent in the Cretaceous. Indications of tectonic activity that create the lithology in Lampung Province need more geological study, especially to determine the absolute age of the metamorphic rock.

Building YoloV4 models for identification of rock minerals in thin section

Rock mineral identification is a costly and time-consuming task using conventional methods of testing physical and chemical properties, especially in the petrographic laboratory. A comprehensive identification model for three rock minerals in sedimentary rocks based on the YoloV4 model is available as a solution. The models predict rock minerals by calculating the pixels and the weights that have been trained previously. First, the YoloV4 models and framework were built. Then, a total of 44 manually labelled thin section images (sedimentary rocks thin section) were used to create the model to detect minerals accurately. The MAP and loss results showed that the parameters of the minerals detection model in PPL are 11% and 1.19, respectively. Meanwhile, The MAP and loss results of XPL are 19% and 1.18, respectively. Finally, Identification of rock minerals using deep learning algorithms is a very promising idea especially the YoloV4 model can build a comprehensive detection of rock samples in thin sections effectively.

Adopted Factorial and New In-Situ Micro-Designs for Stimulation of Matrix Acidizing of Carbonate Reservoir Rocks

Matrix acidizing has been developed in the petroleum industry for improving petroleum well productivity and minimizing near-wellbore damage. Mud acid (HF: HCl) has gained attractiveness in improving the porosity and permeability of reservoir formation. However, there are several challenges facing the use of mud acid, comprising its corrosive nature, high pH value, formation of precipitates, high reaction rate and quick consumption. Therefore, different acids have been developed to solve these problems, including organic-HF or HCl acids. Some of these acid combinations proved their effectiveness in being alternatives to mud acid in reservoir rock acidizing. The current research deals with a new acid combination based on Hydrochloric–Oxalic acids for acidizing carbonate core samples recovered from Qamchuqa Formation in Kirkuk oilfield, northern Iraq. A new in-situ micro-model adopted laboratory technique is utilized to study the microscale alteration and evolution of pore spaces, dissolved grains and identification of matrix acidizing characteristics. The in-situ micro-model is based on the injection of an identical dose of different concentrations of the new acid combination into thin section samples under an optical light microscope. The adopted procedure aims to provide unique and rapid information regarding the potential for texture and porosity modification that can be caused by the acidizing stimulation procedure. In connection, solubility tests for the untreated and treated reservoir core samples and the density of the combined acids after treatment are conducted based on designed experiments using response surface methodology (RSM). The effect of acid concentration [12% HCl: Oxalic acid (3.8–8.8%)] and acidizing temperature (from ambient to 78.8 °C) on the solubility percentage of the samples and percentage increase in the combined acid density after acidizing were optimized and modeled. The obtained results confirm that the optimum dissolution of the core samples took place using 12% HCl:3.2% Oxalic acid with an optimum solubility (%) of the carbonate core rock of 53.78% at 21.7 °C, while the optimum increase in density (%) of the combined acids was 1.54% at 78.3 °C. The promising results could be employed for matrix acidizing of carbonate reservoir rocks for other oilfields.

Organic preservation of vase-shaped microfossils from the late Tonian Chuar Group, Grand Canyon, Arizona, USA.

Vase-shaped microfossils (VSMs) are found globally in middle Neoproterozoic (800-730 Ma) marine strata and represent the earliest evidence for testate (shell-forming) amoebozoans. VSM tests are hypothesized to have been originally organic in life but are most commonly preserved as secondary mineralized casts and molds. A few reports, however, suggest possible organic preservation. Here, we test the hypothesis that VSMs from shales of the lower Walcott Member of the Chuar Group, Grand Canyon, Arizona, contain original organic material, as reported by B. Bloeser in her pioneering studies of Chuar VSMs. We identified VSMs from two thin section samples of Walcott Member black shales in transmitted light microscopy and used scanning electron microscopy to image VSMs. Carbonaceous material is found within the internal cavity of all VSM tests from both samples and is interpreted as bitumen mobilized from Walcott shales likely during the Cretaceous. Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) reveal that VSM test walls contain mostly carbon, iron, and sulfur, while silica is present only in the surrounding matrix. Raman spectroscopy was used to compare the thermal maturity of carbonaceous material within the samples and indicated the presence of pyrite and jarosite within fossil material. X-ray absorption spectroscopy revealed the presence of reduced organic sulfur species within the carbonaceous test walls, the carbonaceous material found within test cavities, and in the sedimentary matrix, suggesting that organic matter sulfurization occurred within the Walcott shales. Our suite of spectroscopic analyses reveals that Walcott VSM test walls are organic and sometimes secondarily pyritized (with the pyrite variably oxidized to jarosite). Both preservation modes can occur at a millimeter spatial scale within sample material, and at times even within a single specimen. We propose that sulfurization within the Walcott Shales promoted organic preservation, and furthermore, the ratio of iron to labile VSM organic material controlled the extent of pyrite replacement. Based on our evidence, we conclude that the VSMs are preserved with original organic test material, and speculate that organic VSMs may often go unrecognized, given their light-colored, translucent appearance in transmitted light.

Petrographic Analysis of Rocks in Tanah Puteh and Pulai, Gua Musang, Kelantan

Gua Musang, Kelantan is well known with diversity of rock associations and also rich in mineral resources such as gold and feldspar according to the existence of active mining sites in this area. The diversity of rock associations in Pulai and Tanah Puteh, Gua Musang have been identified and sampled for this study. The objectives are to determine the mineral association and its composition in various rock types as well as its distribution within these areas. Rock and soil samples have been collected for further analyses using petrography and geochemical analysis respectively. Limestone, tuff, shale, chert, phyllite are amongst of the rock types that have been sampled in this study area. The properties of mineral association in the thin section samples (from the rock samples) have been observed in details using optical microscope. Meanwhile, the results of xray fluorescence (XRF) analysis for selected samples have shown that the SiO2 were ranging between 66 to almost 80 wt.%, and Al2O3 varied from 17 to nearly 26 wt.%. The correlation of the mineral composition from chemical analysis are found in accordance with the mineral existence based on the petrographic studies on selected thin sections from Pulai and Tanah Puteh.

Keurusselkä impact structure, Finland—Overview, new observations, and renewed interpretation of the size

AbstractThe Keurusselkä structure is one of Finland's 12 meteorite impact structures—one of the world's oldest (1150 ± 10 Ma) and the largest of its kind in Finland. Findings of numerous well‐formed shatter cones in a wide area have helped define and prove Keurusselkä's impact origin. Keurusselkä is deeply eroded, making estimating its size challenging. Thus, various size ranges are based on the distribution of shatter cones. This study provides an overview of the earlier published studies in light of the unpublished data resulting from 2003 to 2019 field surveys. Two shatter cone outcrops 15 km from each other were sampled during a field survey in 2019. Thin section samples from these sites were studied with a polarizing microscope, and shock metamorphic features were identified and measured with the universal stage. We also compared topographic and bathymetric Lidar (light detection and ranging) data with the existing geophysical data and shatter cone occurrences. In situ outcrops—Metsomäki 9.6 km toward the W and Martinniemi 5.7 km toward SE from the crater's center—delimit the maximum radius of shatter cones found so far. Studies resulted in planar fractures parallel to (0001) in Metsomäki shatter cones. We determine the size of 37.5 km as the apparent diameter of the Keurusselkä impact structure, whereas the 25 km in diameter semicircular feature represents faulted rim structures.

Geochemical and Petrographic Analyses on Middle and Upper Palaeolithic Cherts from the Central Region of Mediterranean Iberia

ABSTRACT This paper presents the geochemical and petrographic characterization, along with the macroscopic observations, of several cherts from the central region of the Mediterranean Iberia. To determine the microfacies and microtextural features, thin-section samples were analyzed using polarizing light microscopy (PLM) and scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer (SEM/EDX). Geochemical analyses were performed using instrumental neutron activation analyses (INAA). With the data, multivariate statistical analysis by means of hierarchical cluster analysis (HCA) and principal components analysis (PCA) was applied to the chemical variables to identify clusters among the chert samples. The results showed different geochemical features between cherts concerning major, minor, and trace elements. Archaeological samples from different sites demonstrated lithic raw material circulation and, thus, human mobility in the central region of Mediterranean Iberia during the Middle and Upper Paleolithic.

Electrochemical Intelligent Recognition of Mineral Materials Based on Superpixel Image Segmentation.

In order to study the needs of identifying rock thin-section samples by manual observation in the field of geology, a method of electrochemical intelligent recognition of mineral materials based on superpixel image segmentation is proposed. The image histogram of this method can be used to represent the distribution of each pixel value of the image. This interval is consistent with the number of pixels in the method. And using the experiment, the CPU used in the experiment is Intel® Core™ i7-8700 3.2 GHz, the memory is 16 GB, and the GPU is NVIDIA GeForce GT × 1080 Ti, which ensures the accuracy of the experiment. Based on all the experimental results, it can be seen that after the two-stage processing of the designed superpixel algorithm and the region merging algorithm, the final sandstone slice image segmentation results are close to the results of manual labeling, which is helpful for the subsequent research on sandstone component identification. The feasibility of this method was verified.

Origin of dolomites in Lower-Middle Ordovician carbonate rocks in the Yingshan Formation, Gucheng Area, Tarim Basin: Evidence from petrography and geochemical data

Various degrees of dolomitization are widely present in the Yingshan Formation in the Gucheng area of the Tarim Basin. To determine the petrological characteristics and origin of the massive dolomites present, a rich combination of tools was well used, including previous research results, core and thin-section samples, cathodoluminescence, carbon (C-) and oxygen (O-) isotopes, strontium (Sr-) isotopes and content, and burial-thermal history data. The results of this analysis successfully reveal three primary matrix dolomites and three special cements, as follows: (1) microcrystalline to very fine crystalline nonplanar-a dolomite (MD1); (2) very fine to fine crystalline planar-s to planar-e dolomite (MD2); (3) medium to coarse crystalline nonplanar-a to planar-s dolomite (MD3); (4) coarse crystalline nonplanar-a saddle dolomite cement (SD) and (5) medium to coarse crystalline calcite cements (C1 and C2). Among them, MD1 precipitated from the reflux of mildly evaporated seawater, and MD2 was formed by the first significant recrystallization of MD1 in shallow burial environments. In particular, some MD3 was formed by the second significant recrystallization of MD1 in medium-burial environments. The others, even SD, were likely the products of the third significant recrystallization and cementation in deep-burial environments that precipitate under the action of a hydrothermal fluid mixture composed of mantle-derived fluid and Cambrian thermal brine. In addition, C1 and C2 would form close to the times in which the Himalayan and Late Caledonian–Early Hercynian hydrocarbon charging events occurred, respectively.

An investigation of the effect of different aggregate types on concrete properties with thin section and nondestructive methods

Concrete is the most important material in construction industry. Aggregate is one of the most important components of concrete, which consists of many different components. In this study, concrete of constant water/cement ratio was produced by using different types of aggregates, and the effect of aggregate on concrete properties was investigated. After determining the physical properties of the aggregates, the textural properties of the aggregates were investigated with the help of image analysis. Standard water cure was applied to concrete test samples for 7, 28, 90, and 180 days. After the curing process, the physical and mechanical properties of the samples were determined by destructive and nondestructive methods. Thin section samples were taken from hardened concrete samples, and cement aggregate interface investigations were performed under microscope. As a result, it has been determined that aggregate type creates a change in concrete strength, and this situation is related to aggregate properties.

Using Fission-Track Radiography Coupled with Scanning Electron Microscopy for Efficient Identification of Solid-Phase Uranium Mineralogy at a Former Uranium Pilot Mill (Grand Junction, Colorado)

At a former uranium pilot mill in Grand Junction, Colorado, mine tailings and some subpile sediments were excavated to various depths to meet surface radiological standards, but residual solid-phase uranium below these excavation depths still occurs at concentrations above background. The combination of fission-track radiography and scanning electron microscope energy-dispersive X-ray spectroscopy (SEM-EDS) provides a uniquely efficient and quantitative way of determining mineralogic associations of uranium that can influence uranium mobility. After the creation of sample thin sections, a mica sheet is placed on those thin sections and irradiated in a nuclear research reactor. Decay of the irradiated uranium creates fission tracks that can be viewed with a microscope. The fission-track radiography images indicate thin section sample areas with elevated uranium that are focus areas for SEM-EDS work. EDS spectra provide quantitative elemental data that indicate the mineralogy of individual grains or grain coatings associated with the fission-track identification of elevated uranium. For the site in this study, the results indicated that uranium occurred (1) with coatings of aluminum–silicon (Al/Si) gel and gypsum, (2) dispersed in the unsaturated zone associated with evaporite-type salts, and (3) sorbed onto organic carbon. The Al/Si gel likely formed when low-pH waters were precipitated during calcite buffering, which in turn retained or precipitated trace amounts of Fe, As, U, V, Ca, and S. Understanding these mechanisms can help guide future laboratory and field-scale efforts in determining long-term uranium release rates to groundwater.

The acid test: An experimental microarchaeological study of guano-driven diagenesis in tropical cave sediments

Caves in tropical regions form a key resource for those reconstructing human evolution and dispersals. However, the complex sedimentary records they contain remain under-interpreted because of the poorly constrained effects of humid tropical climates upon archaeological site formation processes. Guano-driven phosphatic diagenesis impacts archaeological preservation in caves, but atypical features observed in guano layers in prominent Southeast Asian archaeological sites suggested that hot and humid conditions had promoted the formation of distinctive sedimentary environments with unknown effects on assemblage taphonomy. Few reference data exist that are relevant to geomorphic processes in tropical caves and this laboratory-based modern analogue study was designed to conclusively relate analytical observations to sedimentary palaeoenvironments and explore their effects on assemblage taphonomy. Stratigraphic models were kept under simulated tropical conditions, each containing an identical range of faunal remains, organic materials and minerals, which was buried in wet bat guano. These were excavated, one per month over 24 months, while nine further stratigraphic models were used to control for environmental variables. Sedimentary environments were investigated using sedimentological characterisations of excavated sediments, while post-depositional alterations to buried materials were investigated through optical and scanning electron microscopic analysis of thin-section samples combined with chemical characterisations of excavated samples through Fourier-transform infrared spectroscopy (FTIR). Experimental conditions prevented the sediment acidification that is typically associated with guano-driven diagenesis, but buried materials were severely, and distinctively, diagenetically altered. Organic decomposition in guano, bamboo and charcoal was associated with the activities of sulphate-reducing bacteria, but diagenetic alterations affecting charcoal remain poorly resolved due to variation in the experimental assemblage. Bone was discoloured and affected by dissolution, recrystallisation and alteration to secondary minerals, including gypsum, while carbonates reprecipitated as calcium phosphates and non-stochiometric mineral species. Diagenesis of clay minerals was observed, but related diagenetic trajectories remain poorly resolved. These alterations provide micromorphological and mineralogical indicators of sedimentary palaeoenvironments in the earliest stages of burial and this experiment provides a framework within which to understand the taphonomy of archaeological materials in tropical caves.

Rare-earth elements in the ore of the Bukukinskoye tungsten deposit (the Eastern Transbaikalia)

Research subject. This study investigated the mineral association of quartz-wolframite veins of the Bukukinskoye tungsten deposit, with a particular focus on the content of rare-earth elements and their carrier minerals, their chemical composition and the distribution of light and heavy lanthanides. Materials and methods. The chemical composition of two groups of samples containing different ore minerals, as well as the mineral composition of ores was investigated on 143 samples in thin and polished sections using an AXIO ScopeAI optical polarizing microscope and a LEO 1430 VP scanning electron microscope. Chemical examination of ores was carried out using the ISP MS method. Results. The study of the chemical composition of group samples determined that the content and distribution of REE, the ratio of light and heavy lanthanides in ores depends on the ratio of wolframite and other ore minerals, associated with fluorite and apatite. The main REE concentrator mineral in the wolframite-sulfide-quartz ores of the Bukukinskoye deposit is monazite-(Ce) containing (wt %) Ce (27.09–31.59) La (13.13–17.67), Nd (5.59–10.26), Pr (up to 2.86), Sm (up to 1.14), Th (up to 6.59). Conclusion. The obtained results confirmed our earlier findings for the wolframite of the Sherlova Gora that an increase in the concentration coefficient of heavy lanthanides depends on a decrease in their ionic radius. The contents, mineral forms and ratios of REE of the cerium and yttrium groups in the ore of the Bukukinskоyе deposit can be typochemical signs of greisen tungsten deposits, thus being useful for typification of ore formation in geological forecasting and prospecting.

EARLY METAL AGE POTTERY FROM FATU AKI ANIK KNUA, TIMOR-LESTE AND THE APPEARANCE OF CERAMICS IN THE WALLACEAN ISLANDS SUPPLEMENTARY FILE 1: FAAK CAVE CATALOGUE

This catalogue presents descriptions on 16 diagnostic shards: rims (11), decorated rims (3), and decorated body shards (2) from the Faak Cave.