Mineral identification using data-mining in hyperspectral infrared imagery

Les applications de l’imagerie infrarouge dans le domaine de la géologie sont principalement des applications hyperspectrales. Elles permettent entre autre l’identification minérale, la cartographie, ainsi que l’estimation de la portée. Le plus souvent, ces acquisitions sont réalisées in-situ soit à l’aide de capteurs aéroportés, soit à l’aide de dispositifs portatifs. La découverte de minéraux indicateurs a permis d’améliorer grandement l’exploration minérale. Ceci est en partie dû à l’utilisation d’instruments portatifs. Dans ce contexte le développement de systèmes automatisés permettrait d’augmenter à la fois la qualité de l’exploration et la précision de la détection des indicateurs. C’est dans ce cadre que s’inscrit le travail mené dans ce doctorat. Le sujet consistait en l’utilisation de méthodes d’apprentissage automatique appliquées à l’analyse (au traitement) d’images hyperspectrales prises dans les longueurs d’onde infrarouge. L’objectif recherché étant l’identification de grains minéraux de petites tailles utilisés comme indicateurs minéral -ogiques. Une application potentielle de cette recherche serait le développement d’un outil logiciel d’assistance pour l’analyse des échantillons lors de l’exploration minérale. Les expériences ont été menées en laboratoire dans la gamme relative à l’infrarouge thermique (Long Wave InfraRed, LWIR) de 7.7m à 11.8 m. Ces essais ont permis de proposer une méthode pour calculer l’annulation du continuum. La méthode utilisée lors de ces essais utilise la factorisation matricielle non négative (NMF). En utlisant une factorisation du premier ordre on peut déduire le rayonnement de pénétration, lequel peut ensuite être comparé et analysé par rapport à d’autres méthodes plus communes. L’analyse des résultats spectraux en comparaison avec plusieurs bibliothèques existantes de données a permis de mettre en évidence la suppression du continuum. Les expérience ayant menés à ce résultat ont été conduites en utilisant une plaque Infragold ainsi qu’un objectif macro LWIR. L’identification automatique de grains de différents matériaux tels que la pyrope, l’olivine et le quartz a commencé. Lors d’une phase de comparaison entre des approches supervisées et non supervisées, cette dernière s’est montrée plus approprié en raison du comportement indépendant par rapport à l’étape d’entraînement. Afin de confirmer la qualité de ces résultats quatre expériences ont été menées. Lors d’une première expérience deux algorithmes ont été évalués pour application de regroupements en utilisant l’approche FCC (False Colour Composite). Cet essai a permis d’observer une vitesse de convergence, jusqu’a vingt fois plus rapide, ainsi qu’une efficacité significativement accrue concernant l’identification en comparaison des résultats de la littérature. Cependant des essais effectués sur des données LWIR ont montré un manque de prédiction de la surface du grain lorsque les grains étaient irréguliers avec présence d’agrégats minéraux. La seconde expérience a consisté, en une analyse quantitaive comparative entre deux bases de données de Ground Truth (GT), nommée rigid-GT et observed-GT (rigide-GT: étiquet manuel de la région, observée-GT:étiquetage manuel les pixels). La précision des résultats était 1.5 fois meilleur lorsque l’on a utlisé la base de données observed-GT que rigid-GT. Pour les deux dernières epxérience, des données venant d’un MEB (Microscope Électronique à Balayage) ainsi que d’un microscopie à fluorescence (XRF) ont été ajoutées. Ces données ont permis d’introduire des informations relatives tant aux agrégats minéraux qu’à la surface des grains. Les résultats ont été comparés par des techniques d’identification automatique des minéraux, utilisant ArcGIS. Cette dernière a montré une performance prometteuse quand à l’identification automatique et à aussi été utilisée pour la GT de validation. Dans l’ensemble, les quatre méthodes de cette thèse représentent des méthodologies bénéfiques pour l’identification des minéraux. Ces méthodes présentent l’avantage d’être non-destructives, relativement précises et d’avoir un faible coût en temps calcul ce qui pourrait les qualifier pour être utilisée dans des conditions de laboratoire ou sur le terrain.The geological applications of hyperspectral infrared imagery mainly consist in mineral identification, mapping, airborne or portable instruments, and core logging. Finding the mineral indicators offer considerable benefits in terms of mineralogy and mineral exploration which usually involves application of portable instrument and core logging. Moreover, faster and more mechanized systems development increases the precision of identifying mineral indicators and avoid any possible mis-classification. Therefore, the objective of this thesis was to create a tool to using hyperspectral infrared imagery and process the data through image analysis and machine learning methods to identify small size mineral grains used as mineral indicators. This system would be applied for different circumstances to provide an assistant for geological analysis and mineralogy exploration. The experiments were conducted in laboratory conditions in the long-wave infrared (7.7μm to 11.8μm - LWIR), with a LWIR-macro lens (to improve spatial resolution), an Infragold plate, and a heating source. The process began with a method to calculate the continuum removal. The approach is the application of Non-negative Matrix Factorization (NMF) to extract Rank-1 NMF and estimate the down-welling radiance and then compare it with other conventional methods. The results indicate successful suppression of the continuum from the spectra and enable the spectra to be compared with spectral libraries. Afterwards, to have an automated system, supervised and unsupervised approaches have been tested for identification of pyrope, olivine and quartz grains. The results indicated that the unsupervised approach was more suitable due to independent behavior against training stage. Once these results obtained, two algorithms were tested to create False Color Composites (FCC) applying a clustering approach. The results of this comparison indicate significant computational efficiency (more than 20 times faster) and promising performance for mineral identification. Finally, the reliability of the automated LWIR hyperspectral infrared mineral identification has been tested and the difficulty for identification of the irregular grain’s surface along with the mineral aggregates has been verified. The results were compared to two different Ground Truth(GT) (i.e. rigid-GT and observed-GT) for quantitative calculation. Observed-GT increased the accuracy up to 1.5 times than rigid-GT. The samples were also examined by Micro X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) in order to retrieve information for the mineral aggregates and the grain’s surface (biotite, epidote, goethite, diopside, smithsonite, tourmaline, kyanite, scheelite, pyrope, olivine, and quartz). The results of XRF imagery compared with automatic mineral identification techniques, using ArcGIS, and represented a promising performance for automatic identification and have been used for GT validation. In overall, the four methods (i.e. 1.Continuum removal methods; 2. Classification or clustering methods for mineral identification; 3. Two algorithms for clustering of mineral spectra; 4. Reliability verification) in this thesis represent beneficial methodologies to identify minerals. These methods have the advantages to be a non-destructive, relatively accurate and have low computational complexity that might be used to identify and assess mineral grains in the laboratory conditions or in the field

Definition of a genetic model for the dark-colored overgrowths in pegmatitic gem tourmaline crystals

Elba gem tourmalines are renowned for the delicate pastel colors and the perfection of their crystal shapes in small size. Characteristic for these tourmalines is the presence of color anomalies that occur as dark-colored terminations, frequently at the analogous pole that typically are rich in Fe and/or Mn. The formation of such dark-colored overgrowths is related to sudden physicochemical changes in the crystallization environment during the latest-stages of tourmaline crystal growth. However, the detailed events that led to the availability of Fe and/or Mn in the pocket environment, resulting in the growth of late-stage tourmalines, remained unclear. The goal of this Ph.D project is the definition of a genetic model for the dark-colored overgrowths in pegmatitic gem tourmaline crystals. Since tourmaline is an excellent petrogenetic indicator, the origin and chemical composition of fluids involved in tourmaline crystallization, responsible for such color anomalies, have also been investigated. To achieve this goal, selected gem tourmaline crystals with dark overgrowths of different colors and textural features from several miarolitic Li-bearing aplite-pegmatite veins, located in the eastern border of Monte Capanne monzogranite pluton (Elba Island, Italy), were studied. Chemical and spectroscopic investigations were applied as experimental approach in order to describe the crystal-chemical characteristics of the zones characterized by such color anomalies. This information, along with microstructural and paragenetic observations of the cavities in which the studied tourmaline samples were collected, were used to determine and propose a general genetic model for the color anomalies observed at the termination of Elba gem tourmaline crystals. This study was further extended to tourmaline samples collected from the Alto Ligonha pegmatite district (Nampula Province, NE Mozambique). Gem-quality tourmalines from the Alto Ligonha pegmatite district are among the most renowned for the combination of color and rarity. These features make them unique from a gemological viewpoint and therefore with a high commercial value, limiting the information regarding their crystal-chemical characteristics. To fill this gap, several tourmaline samples from the secondary deposit of Mavuco, in the eastern portion of the Alto Ligonha pegmatite district, were studied. These tourmaline samples were provided by ongoing mining projects, and were subjected to an in-depth analysis. Specifically, a detailed chemical characterization as well as a correlation study between compositional data and color displayed by the tourmaline crystals, were conducted. In addition, on selected samples with particular chromatic features, optical absorption spectroscopy analyses were performed. For all the tourmaline samples analyzed, the gemological variety, according to the color displayed, was identified and the relative color mechanisms were investigated. Tourmaline grains from the secondary deposit of Mavuco are also characterized by a dark-colored prismatic overgrowth. The genetic mechanisms responsible for these prismatic overgrowths have not been defined so far, as the pegmatitic source from which these tourmalines originated was still uncertain. This uncertainty was essentially due to the strong NYF (Niobium-Yttrium-Fluorine) geochemical affinity (Li- and B-poor composition) of the Alto Ligonha pegmatites located quite close the secondary deposit of Mavuco, as well as the rudimentary excavation techniques, which did not allow the exploration of new pegmatitic deposits in the Alto Ligonha district. To gain information about the processes that led to the formation of the prismatic dark-colored overgrowths, selected tourmaline crystals from a recently discovered pegmatitic field, the so-called “Marina” pegmatite (Mavuco area), were analyzed. The “Marina” pegmatite was hypothesized to be a source of the detrital tourmaline grains of the Mavuco area, given its proximity to the secondary deposit, and its LCT geochemical signature. Studies on tourmaline crystals from the “Marina” pegmatite were carried out to confirm the above hypothesis, through the comparison of the compositional data obtained from such tourmaline crystals with those obtained from the detrital tourmalines of the secondary deposit of Mavuco. The same studies allowed obtain detailed information on the genesis of the dark-colored prismatic overgrowths, which also characterize some of the detrital tourmalines. During the chemical characterization activity, two new mineral species of the tourmaline supergroup were discovered. Both of them were approved by the IMA-CNMNC (International Mineralogical Association-Commission on New Minerals, Nomenclature and Classification) and named celleriite, ideally □(Mn2+2Al)Al6(Si6O18)(BO3)3(OH)3(OH), and ferro-bosiite, ideally NaFe3+3(Al4Fe2+2)(Si6O18)(BO3)3(OH)3O. The results obtained in this PhD research improved the knowledge on the opening of geochemical systems in which tourmaline crystallized, and allowed the definition of a genetic model for the formation of the dark-colored overgrowths in tourmaline crystals. This model can be exported to explain late-stage color and composition anomalies of gem tourmaline crystals of many other gem-pegmatite deposits in the world

Pegmatites of the Anderson Ridge quadrangle, Fremont County, Wyoming

“The oldest rocks in the area consist mainly of para- schists of low to medium rank and restricted higher rank sillimanite schist. The entire series has been at least double folded. The most apparent are tight north to north- east trending folds. These have been intruded in the northern part of the area by a batholithic body of granitic composition, a granitic stock, a pegmatitic granite, a granitic sill-like body and different types of pegmatite dikes and sills. The youngest intrusions are a series of northeast trending basic dikes and sills. A major easterly trending transverse fault and a series of smaller faults of almost east-west trend are the main fault trends in the area. They are younger than all bodies above. Pegmatites are very abundant and vary in size, shape, texture, and mineralogy. They are more numerous in the north than the south and invade all rock types except the younger basic intrusions. A new classification of the size, shape, and texture of pegmatites is proposed. The size and shape of any individual pegmatite body is identified by two values, namely, the length X width (LXW) value and the length/width (L/W) ratio. Because of the extreme variation in texture of the pegmatite bodies a classification based on a geometric scale is proposed. Both mega- and microscopic sizes applicable to field and laboratory studies are included. Five different mineralogioal types of pegmatites are recognized: magnetite granite, graphic granite, tourmaline granite, garnet granite, and biotite granite. Both concordant and discordant types of pegmatites are present. A few of the concordant varieties show a rough zoned character, but layering is characteristic of the discordant and many of the concordant varieties. The layering may result from textural and/or compositional variations. Coarse and very coarse bands alternate with fine and very fine ones. Also distinct mineralogic variations are common in these different bands. Fine-grained red garnet-rich bands characterize a good percentage of the pegmatites in the area. These colored bands are of great help in determining the internal structure of such bodies. The pegmatites are believed to be of magmatic origin. The temperature of the magmatic fluids, the content of volatiles, and the confining pressure as well as the chemical composition are thought to have varied greatly for the different pegmatite types of the area. Beryl is the most important economic mineral known to date. The very coarse tourmaline granite pegmatites are the most important host for beryl. Coarse perthitic bands and massive quartz bands in the tourmaline garnet granite pegmatites and the garnet granite pegmatites offer some promise as hosts for beryllium minerals. The district is now under active exploration”—Abstract, pages iii-iv

High-resolution heavy mineral studies on “black sands” from the Nama Group (Fish River Subgroup) in Namibia – Part II.

Master's thesis in Petroleum Geosciences Engineering“Black sands” from a presumed heavy mineral placer of the Nama Group in Namibia will be studied in detail. The samples for this thesis are collected from various outcrops belonging to the Fish River Subgroup in the Nababis Formation. This formation lies in the Nama Basin, in which the Haribes Member is deposited. High-resolution heavy mineral stratigraphy for the succession will be used to determine provenance of the detrital material. To achieve this, a methodical approach will be used where geochemistry, XRD (X-Ray Diffraction), and semi-quantification of heavy minerals using MLA (Mineral Liberation Analyzer) are combined with FEG-SEM-BSE-EDS-CL (Field Emission Gun Scanning Electron Microscope, Back Scattered Electron, Energy Dispersive Spectrometer and Cathodoluminescence). Heavy mineral size distribution suggests normal size distribution with peaks around 125-150 microns for all samples, with one exception, Zf 409, which has bimodal size distribution in the range of 75 – 125 microns. Furthermore, all heavy mineral particles are generally angular to sub-angular, which can infer a short transportation route. The samples display relative similar mineralogy according to FEG-SEM and MLA analyses. One can suggest a proximal metamorphic source based on findings of i.e. chamosite, garnets, clinopyroxene, as well as the possibility of the identified grossular are Ca-epidotes according to XRD analysis. Moreover, the chemical composition of garnets was plotted in ternary diagrams, which show evidence of amphibolite facies and metabasic rock associations. Provenance studies can be very useful to determine the tectonic setting of the sedimentary successions and the detrital material. By determining the main characteristics of the depositional basins and the source areas of the deposited detritus, it is possible to understand sedimentological processes. This is one of the important sources of information for the mineral and petroleum industry that need to evaluate potential plays

Raja Au-Co mineralization in the Paleoproterozoic Peräpohja belt:on the occurrence of tourmaline, anhydrite and gypsum proximal to the mineralization

Abstract. The Raja Au-Co mineralization in the Paleoproterozoic (2.5–1.8 Ga) Peräpohja belt in northern Finland is a part of the wider Rompas-Rajapalot area with several known Au occurrences. The area is characterized by a distinct occurrence of tourmaline, locally spatially associated with the known mineralizations. In addition, recently, an unusual rock unit with bright purple anhydrite and white gypsum veins has been intersected by diamond drilling. While the sulfate-rich unit is non-mineralized, the atypical mineralogy and close spatial association to the Raja mineralization is interesting. In this master’s thesis, the occurrence of tourmaline and sulfates are studied, and their relationship to the Raja mineralization is examined. In-situ geochemical, major and trace elements, and boron isotopic data of tourmaline were obtained by EPMA and LA-ICP-MS from thin section samples prepared from Raja drill core. The analytical data was used to complement the petrographic observations from thin sections, and to quantitatively evaluate tourmaline chemical composition. Additionally, orientations of quartz-tourmaline veins from drill core samples were measured and analyzed with stereographic projections. In-situ sulfur isotope data was obtained for the sulfate phases by LA-ICP-MS. Three texturally different types of tourmaline are identified: 1. Coarse grained euhedral tourmaline as abundant dissemination in metasomatic bands, 2. Tourmaline in quartz-tourmaline veins crosscutting the host rock, and 3. Rare footwall tourmaline in healed microfractures, and associated to ambiguous pegmatitic quarts-felspar-mica veins. All assayed tourmaline belongs to alkali-group and are classified as dravite. They have variable chemical composition that suggests crystallization in reduced and low- to moderate saline conditions. Tourmaline geochemistry together with boron isotope data (δ11B from -11.5 to -0.9 ‰) suggests that tourmaline could have formed from mixed fluid source: from devolatilization of clastic metasedimentary rocks or non-marine evaporites, and granites or pegmatites. Orientation data from the quartz-tourmaline veins outlines a stronglinear trend towards 340° that matches within few degrees with the Raja high-grade mineralization trend. This is seen as evidence of the structural control for theRaja mineralization, which possibly is contained in local shear-zone or hinge region of local higher degree folding. In Raja, anhydrite has δ 34S values in a narrow range from 8.07 to 9.77 ‰. Gypsum has slightly heavier δ 34S from 10.63 to 12.19 ‰. Textural evidence together with isotope fractionation constraints suggests authigenic formation of gypsum with SO4 2- sourced from anhydrite. Significant similarities in sulfur isotope values, and textural evidence (pseudomorphs after evaporite minerals, folded anhydrite bands), to well-known evaporite succession in Onega basin, western Russia, suggest that the sulfates in Raja might represent preserved Paleoproterozoic sulfate evaporites, which, if true, can have important regional metallogenic and scientific implications.Varhaisproterotsooinen Rajan Au-Co mineralisaatio Peräpohjan liuskejaksolla : turmaliinin, anhydriitin ja kipsin esiintyminen mineralisaation läheisyydessä. Tiivistelmä. Rajan kulta-koboltti -mineralisaatio varhaisproterotsooisella (2.5–1.8 miljardia vuotta sitten) Peräpohjan liuskejaksolla on osa laajempaa Rompas-Rajapalojen aluetta, josta tunnetaan useita kultaesiintymiä. Turmaliini on yleinen mineraali alueen esiintymien yhteydessä. Lisäksi viimeaikaisten syväkairausten yhteydessä on löydetty anhydriitti-kipsipitoinen kivilajiyksikkö, joka on mielenkiintoinen alueen geologisen evoluution selvittämiseksi. Tässä pro gradu -tutkielmassa selvitetään turmaliinin ja sulfaattien esiintymistä sekä niiden yhteyttä Rajan mineralisaatioon. Tutkimusta varten Rajan kairasydännäytteistä valmistettiin ohuthieitä, jotka analysoitiin elektronimikroanalysaattorilla sekä LA-ICP-MS -menetelmällä turmaliinin geokemian ja boori-isotooppikoostumuksen selvittämiseksi. Kvantitatiivista analyyttistä dataa käytettiin yhdessä perinteisen mikroskooppisen tutkimuksen kanssa turmaliinien luokitteluun sekä petrologiseen tulkintaan. Lisäksi kairasydännäytteiden kvartsi-turmaliinijuonista tehtiin rakenteellisia suuntamittauksia, joita tulkittiin graafisten kuvaajien avulla. Sulfaattifaaseista määritettiin rikin isotooppikoostumus LA-ICP-MS -menetelmällä. Tutkimuksessa tunnistettiin kolme tekstuuriltaan erilaista turmaliinityyppiä: 1. Karkearakeinen ja omanmuotoinen turmaliini, joka esiintyy runsaina kasaumina metasomaattisissa vyöhykkeissä, 2. Turmaliini isäntäkiveä leikkaavissa kvartsi-turmaliini juonissa, ja 3. Harvemmin esiintyvä turmaliini Rajan mineralisaation jalkapuolella parantuneissa mikroraoissa sekä epämääräisten pegmatiittisten kvartsi-maasälpä-kiille -juonien yhteydessä. Geokemialtaan kaikki analysoidut turmaliinit kuuluvat alkaliryhmään ja luokitellaan draviiteiksi. Turmaliinin kemiallinen koostumus viittaa mineraalin kiteytyneen pelkistävissä ja suolaisuudeltaan matalan tai keskitason olosuhteiden vallitessa. Mitatut booriisotooppiarvot (δ 11B välillä -11.5 ja -0.9 ‰) yhdessä turmaliinin geokemian kanssa viittaavat turmaliinin mahdollisesti kiteytyneen kahden toisistaan eroavan fluidin läsnäollessa, joista ensimmäinen voi olla peräisin klastisista metasedimenteistä tai mantereen sisäisten järvialaiden evaporiiteista, ja toinen graniiteista tai pegmatiiteista. Kvartsiturmaliinijuonista mitattu rakennedata asettuu graafisesti esitettynä noin 340° suuntaisesti, vastaten läheisesti Rajan mineralisaation suuntausta. Mineralisaation ja juonten esiintymistä ohjaa todennäköisesti sama rakenteellinen piirre, joka voi olla paikallinen hiertovyöhyke tai korkeamman asteen poimujen harjavyöhyke. Sulfaateista mitatut δ 34S arvot vaihtelevat kapealla välillä (δ 34Sanhydriitti = 8.07–9.77 ‰, δ 34Skipsi = 10.63–12.19‰). Mikroskooppiset tekstuurit ja isotooppifraktioitumisen rajoitteet viittaavat kipsin kiteytyneen paikallisesti anhydriitistä liuenneesta sulfaatista (SO4 2- ). Merkittävät yhteneväisyydet rikki-isotooppiarvoissa verrattuna Venäjän länsiosan hyvin säilyneisiin evaporiittimuodostumiin, sekä Rajalta havaitut korvautuneita evaporiittimineraaleja mukailevat karbonaattipseudomorfit, viittaavat Rajan sulfaattien edustavan varhaisproterotsooisia sulfaattievaporiitteja. Mikäli tämä pitää paikkansa, evaporiittiesiintymien olemassaololla on merkittäviä tieteellisiä ja alueellisia malmigeologisia seurauksi

Evidence for fluid-assisted shear failure in a ductile shear zone: tectonic tremor in the geologic record?

Includes bibliographical references.2015 Summer.Recent direct observations of tectonic tremor below the seismogenic zone of large fault zones have emphasized the significance of coeval ductile and brittle processes at high temperatures. Tectonic tremor is defined as long-duration, low-amplitude, and low-frequency seismic signals produced at depths of 18-40 km. Because the source of tremor is currently unknown, the physical conditions and processes that cause tremor are unknown. This study presents observations of an exhumed shear zone system contained within the Saddlebag Lake pendant of the eastern Sierra Nevada, California. The high-strain rocks in this shear zone exhibit multiple episodes of vein formation, indicating a prolonged migration of hydrothermal fluids through the system. Crosscutting relationships and mineral assemblages define discrete sets of variously oriented veins that are folded and boudinaged. I document foliation-parallel quartz veins that show shear displacement parallel to the foliation. Textural evidence for dynamic recrystallization mechanisms, stable isotope data, and fluid inclusion thermobarometry measurements indicate temperatures between 300-680°C and relatively high fluid pressure conditions, greater than σ₃, during fracture. Conditions of nucleation of shear fractures within this ductile shear zone suggest these structures may record similar processes to those under which tectonic tremor is observed in other continental transform fault zones. I interpret that these veins formed as shear fractures under increasing differential stress and fluctuations in pore pressure, with failure driven by heterogeneous materials within the shear zone

A CRITICAL EVALUATION OF CHALLENGES TO MARINE PROTECTED AREAS IN PUERTO RICO

This report, prepared for University of Puerto Rico Mayaguez, is an independent assessment of the challenges to the development and management of marine protect areas (MPA) in Puerto Rico. Through analysis of five established MPA in Puerto Rico and interviews with key stakeholders that were involved in the establishment of MPA, we have documented lessons learned and possible solutions for successful MPA in Puerto Rico

Application of air photograph to porphyry copper exploration

Imperial Users onl