Post-sedimentation Processes Research Articles

Вторичные изменения карбонатных пород Непско-Ботуобинской антеклизы юга Сибирской платформы и их влияние на коллекторские свойства продуктивных горизонтов

Nepa-Botuoba anteclise is one of the most promising territories in Eastern Siberia, within which more than a half of the hydrocarbon resources are connected with carbonate reservoirs. One of the main tasks in the development of oil and gas resources in this region is associated with the forecast of the localization of reservoir rocks, which is largely determined by the degree of knowledge of the post-sedimentation proc-esses which have occurred. The article is dedicated to the influence of secondary processes on the capacitive and filtration properties of productive carbonate rocks of the Nepa-Botuoba anteclise. One of the wells drilled within its northeastern section has been taken as an example. The features of each of the post-sedimentation processes manifestation which took place were examined in detail and their influence on the filtration-capacitive properties of rocks of various lithotypes was assessed for all carbonate horizons penetrated by the well. The results of the research will help to increase the reliability of the forecast for the localization of carbonate rocks with improved capacitive and filtration properties, and therefore increase the efficiency of development of oil and gas resources in the considered region

FIRST RESULTS OF U−Th/He DATING OF EPIGENETIC PYRITE FROM ROCKS OF THE BAZHENOV FORMATION, WESTERN SIBERIA

U–Th/He method was applied to determine the age of epigenetic pyrite from the oil source rocks of the Bazhenov Formation, Western Siberia. Results indicate the possibility to date the post-sedimentation processes in a sedimentary basin by authigenic pyrite U–Th/He dating. The U–Th/He isochron age of pyrite (n = 7) from the dolomites of the Bazhenov Formation within the Frolovskaya megadepression is much younger than the age of sedimentation and corresponds to the Santonian-Cenomanian stages of the Upper Cretaceous (90 ± 8 Ma).

First Results of U–Th/He Dating of Epigenetic Pyrite from Rocks of the Bazhenov Formation, Western Siberia

The U–Th/He method has been applied for the first time to determine the age of epigenetic pyrite from the oil source rocks of the Bazhenov Formation, Western Siberia. The possibility to date the post-sedimentation processes in a sedimentary basin by authigenic pyrite using the U–Th/He method is shown. The U–Th/He isochrone age of pyrite (n = 7) from the dolomites of the Bazhenov Formation within the Frolovskaya megadepression is much younger than the sedimentation age and corresponds to the Santonian–Cenomanian stages of the Upper Cretaceous (90 ± 8 Ma).

Вертикальная трещиноватость как особенность геологического разреза левобережной части АГКМ, влияющая на обводнение эксплуатационных скважин

The left-bank part of the Astrakhan gas condensate field (AGCF) is represented by a carbonate reservoir of a complex type. The study of the geological structure and properties of the deposit is a fundamental factor for its successful operation. There are presented the main characteristics of the lithological composition and filtration-capacitance properties of the carbonate productive reservoir C2b of the left-bank part of the AGCF, described the specific features of their formation. One of the important features of the productive carbonate reservoir of the left-bank part of the AGCF is the anisotropy of filtration-capacitance properties in different directions. Special attention was paid to the description of horizontal and vertical fracturing, and post-sedimentation processes. There is proposed a probable mechanism of fracturing in areas of high occurrence of productive strata. The problem of well flooding is of great importance for the development of AGCF. Different factors of geological and technical order were investigated (the position of drilled faces and perforation intervals/open barrel relative to the position of the gas-water contact). No regularities were revealed. Based on the study of field data, zones of vertical fracturing have been identified, which caused the flooding of wells. It is possible to map watering zones according to the structural parameters of Bashkir deposits at the highest roof marks. There has been suggested a probable model of well flooding in the left-bank part of the AGCF associated with the tectonic factor and post-sedimentation processes of external influence. The actual data are presented, including a diagram of wells with a water-gas factor WGF ≥ 100 cm3/m3 depending on the occurrence of the roof C2b, which clearly confirm the predominance of a crack-pore collector with significant communication in the described zones.

Hydrogeochemical processes and groundwater chemistry in the West Siberia

The present study aimed to identify the formation factors of the current hydrogeochemical character of the Middle-Jurassic aquifer groundwaters (beds YU 2–4) in the Lyaminsky petroleum district of West Siberia in Russia. We hypothesized that the scales of the impact of post-sedimentation processes at the current stage have largely predetermined the character of the Middle-Jurassic aquifer system. To check if the hypothesis is valid, two research problems have been addressed using the lithogenesis theory of the transformation of the groundwater composition during the geologic evolution: we have evaluated factors that governed the genetic type and composition of initial waters (lithologic, paleogeographic), and factors that control subsequent changes in the chemical composition of groundwaters (geotemperatures, neotectonics effect, etc.). To solve the first problem, the formation conditions of groundwaters under study in the continental setting were investigated. To settle the second problem, we obtained the coefficients of correlation between the Middle-Jurassic aquifer groundwater salinity and the current temperature and paleotemperature of the Tyumenian suite, and between the porosity coefficient and the basement depth. We have concluded that the current hydrogeochemical character of the Middle-Jurassic aquifer system is the resultant of the consecutive effects of the whole set of factors.

Нижнесерпуховские карбонатные псефитолиты центральной части гряды Чернышева

The paper presents the results of the study of carbonate psephitolites developed in the Lower Serpukhovian deposits in the Central part of the Chernyshev Ridge. They have different morphology and genesis. There include sedimentation breccia and post-sedimentation intra-formation units, however thick strata of brecciated rocks have the most problematic genesis indicating the formation of these clastic carbonate rocks during sedimentation and post-sedimentation processes. 
 As a result we determined that a shallow sea basin existed on the territory of the central part of the Chernyshev Ridge in the Early Serpukhovian period. In the western part, shallow sediments, including intraplate karst breccias and coastal-marine detrital limestones, were deposited in shoals with island uplifts and lagoons. At the same time, dark-colored limestone silts were accumulated in the deeper sea in the east, and intercalated with removed debritic flows. During the Ural orogeny, due to the layer-by-layer breakdown at the base of the Serpukhovian, thick strata of intensively breccated carbonate deposits were formed. Post-sedimentation processes of changes in the Lower Serpukhovian sediments (recrystallization, dolomitization, partial dissolution) could occur during major Middle and Upper Carboniferous regressions, as well as after the change of the elysial hydrogeological regime to infiltration at the Triassic-Jurassic boundary. They have continued up to the present time. This is especially evident in the eastern part of this territory in areas of increased permeability of rocks. There are intensive processes of leaching, dolomitization, calcitization, and karst developing.

Cyclicity, sedimentation environments and the influence of post-sedimentary processes on the structure and formation of the Vanavara Formation reservoir (based on the analysis results of core material of the Novo-Yudokon field)

The Lower Vendian oil and gas bearing play is one of the main ones in the Siberian platform and dominant within large tectonic elements (Nepa-Botuoba anteclise, Sayan-Yenisei syneclise, etc.). The oil and gas content of the complex is determined both by the conditions of its formation and by post-sedimentation processes, which are largely associated with the stages of formation and reformation of hydrocarbon pool. All these features of Vanavara reservoir were explored in a detailed lithofacies analysis of the core material of the Novo-Yudokon field and adjacent territories.

Lithogenetic preconditions of reservoirs and reservoir rocks formation in the Middle Devonian sediments of the Skhidnosaratske deposit (Dobrudja Foredeep)

The lithological features of the Middle Devonian sediments of the Skhidnosaratska structure of the Dobrudja Foredeep in the aspect of their influence on the formation of reservoir rocks and hydrocarbon reservoirs have been considered. Nine lithocycles of regressive nature (e-1 – e-5; g-1 – g-4), characterized by a two-membered structure have been identified in the section. Each lithocycle represents a separate productive horizon. The lower parts of the latter are composed of porous and fractured reservoir rocks (limestones, dolomites, siltstones, sandstones), and the upper parts are composed of fluid-resistant packs (marls, anhydrites).Features of cyclic sedimentation conditions caused spatial-age variability of trap localization and morphology, nature of distribution of reservoir rocks of various types, and post-sedimentation processes caused spatial heterogeneity of petrophysical properties of rocks, which entailed different prospects for individual areas of the Skhidnosaratske deposit. The vaulted traps of the productive horizons of the Eifelian deposits tend to the area of borehole 2, and the Zhivetian deposits to the borehole 1. Consequently, in the first case, the most perspective horizons are e-2 and e-3, in the second – g-2 – g-4. Often more powerful packs of better-quality reservoir rocks are developed outside the vault, which leads to the formation of lithological traps in the e-1 and e-2 horizons. It has been shown that the complex structure (presence of layers of carbonate and terrigenous rocks) of fluid-resistant marl-sulfate packs could cause dispersion of hydrocarbons and thus reduce the prospects of individual horizons, in particular, e-2 and e-3. The established heterogeneity of the structure of the productive horizons, the pinching out of individual packs of both pore and fractured reservoirs, the spatial uneven development of the limestones anhydritization and dolomitization processes give possibilities to suggest the formation of separate deposits with different hypsometry of water-oil contacts.

MAR comparisons between different chronometric methods for two profiles in the Bodrogkeresztúr area

The deepening and exploration of the loess-palaeosol section at the foot of the Kopasz Hill at Bodrogkeresztúr have been carried out to expand the existing knowledge of the Carpathian foothill palaeoenvironmental factors and their impact. The study deals with particle size analysis, organic matter and carbonate content. For the presentation of age-depth models, the OSL dates of Bodrogkeresztúr (BKT) and the 14C dates of Bodrogkeresztúr, brickyard 1 were used-, and the diagrams of the Accumulation Rates (AR) derived from them. These were compared with Mass Accumulation Rate (MAR) calculations based on OSL and 14C data from BKT and 14C data from Bodrogkeresztúr, brickyard 1. It became evident that there is a significant difference between the two sections, which may be due to the upland position, the overlap, or the wind tunnel effect. Sedimentological studies revealed coarser grain composition, however, the nearly complete absence of coarser sand fraction is also noticeable in the case of BKT. Also, the entire section is characterized by increased carbonate content due to post-sedimentation processes, recarbonization and leaching. The AR and MAR results show the difference between the suitability of different chronometric methods, indicating that the top of both sections may have been redeposited or eroded.

ВИЗУАЛИЗАЦИЯ СТРУКТУРНО-ТЕКСТУРНЫХ ИЗМЕНЕНИЙ В НОВООБРАЗУЮЩЕМСЯ СНЕЖНОМ СЛОЕ ПРИ ДЛИТЕЛЬНОМ СНЕГОПАДЕ

Observations were made on the dynamics of structural and textural transformations in the newly fallen snow layer during its transition to a stratigraphically significant snow accumulation layer. To visualize the structural and textural transformations during a prolonged snowfall and post-sedimentation changes in it after the snowfall stopped, a reflective screen was used in combination with photomicrography of solid precipitation and snow grains. Observations were made for seven days. Already on the third day, with the thickness of the newly formed snow layer of 12 cm, the primary texture in the form of internal layering, due to the microstructure of freshly fallen snow, began to differ in it. In the process of post-sedimentation transformations, the primary stratification in the newly formed stratigraphically significant snow layer was preserved, but became less noticeable. Micrographs showed that the deposited snowflakes were transformed by sublimation metamorphism to form small rounded RGsr particles, which differed little from the snow grains in the underlying layer. It is assumed that the structural and textural post-sedimentation transformations of solid precipitation in the upper part of the snow thickness are more controlled by the depth of penetration of the air temperature gradient. Lower boundary of this upper part is well distinguished in the snow profile owing to the optical anisotropy of the snow horizons composed of RGsr snow grains and FCso and DHla facet crystals. The performed studies demonstrated that the light-reflecting screen can be used in snow science as a simple tool for optical monitoring of structural heterogeneities of seasonal snow cover and visualization of post-sedimentation processes that occur during its growth.

УСЛОВИЯ ФОРМИРОВАНИЯ ПЕСЧАНЫХ ПЛАСТОВ-КОЛЛЕКТОРОВ ЯКОВЛЕВСКОЙ СВИТЫ НА ТЕРРИТОРИИ ЛОДОЧНОГО НЕФТЕГАЗОКОНДЕНСАТНОГО МЕСТОРОЖДЕНИЯ

Актуальность исследования обусловлена необходимостью расширения ресурсного потенциала Российской Федерации за счет прироста месторождений углеводородов. На сегодняшний день нефть относится к полезным ископаемым, достигнутые уровни добычи которых недостаточно обеспечены запасами разрабатываемых месторождений. Подробное изучение строения продуктивных песчаных пластов-коллекторов в пределах Ванкорской группы месторождений на севере Красноярского края в перспективе даст возможность для прогноза и открытия новых залежей углеводородов в нижнемеловых отложениях Сибири. Цель: определить условия формирования продуктивных песчаных пластов по данным изучения кернового материала, изучить причины неоднородности сформированных отложений и выявить их характерные признаки для последующего прогноза нижнемеловых нефтеносных отложений на территории Красноярского края. Объект: продуктивные песчаные пласты яковлевской свиты нижнего мела Лодочного нефтегазоконденсатного месторождения. Методы: петрографический анализ шлифов, стадиальный анализ, гранулометрический анализ, фациальный анализ, исследование фильтрационно-емкостных и петрофизических свойств пород. Результаты. По данным петрографического анализа был изучен вещественный состав продуктивных песчаных отложений верхне- и нижнеяковлевской подсвит Лодочного месторождения, дана их сравнительная характеристика. Определена степень влияния постседиментационных процессов на формирование современного облика изучаемых отложений. Предложена фациальная модель, наиболее точно описывающая условия формирования продуктивных пластов. Установлено влияние условий осадконакопления в комплексе с последующими постседиментационными преобразованиями пород на фильтрационно-емкостные параметры песчаников. Объяснены причины наличия карбонатизированных прослоев во флювиальных отложениях. Сделаны выводы о возможности прогноза продуктивности отложений яковлевской свиты, накопленных в различных фациальных обстановках.

Marking of productive intervals in Bazhenov formation based on a limited set of well testing

The article is devoted to features of the geological structure of Bazhenov formation. The rocks of Bazhenov formation were dissected according to the data of a limited complex of well testing. The presented method is based on qualitative signs of changes in the registered curves, which have a pronounced character of changing values comparable to changes in the spectrometric composition of rocks, paleontological characteristics, the facies situation of sedimentation and secondary post-sedimentation processes occurring in Bazhenov deposits. During the analysis and development of the algorithm, the basic marking horizons were identified, which took into account the main lithological and metamorphic features of the formation's deposits. The presented method of marking differs slightly from the usual lithotypisation of a well section. Its simplicity makes sense to use the minimum amount of available information with the possibility of selecting and testing the most productive intervals of the formation. Successfully conducted testing of algorithms works in two deposits of the different genesis of the sediments, the data obtained are compared are presented with the detailed lithological characteristics selected by the core and the tested wells.

Comparative petrography and organic geochemistry of different types of organic matter occurring in the Outer Carpathians rocks

The characterization of organic matter (OM) in sedimentary rocks is important in many types of biological, geological and environmental research. The integrated use of microscopy and geochemistry, as here, is particularly useful in any attempt to define the origin and evolution of OM in sedimentary basins. The organic petrography and geochemistry different types of allogenic and authigenic OM from the Polish Outer Carpathian (POC) rocks were studied in present study to compare their genetic type, thermal maturity, depositional environment and post-sedimentation processes. Special attention was paid to redeposited coal clasts occurrences. The used techniques show differences in organic matter type originating from various sources. The organic petrography analysis shows that redeposited coal clasts (CC) and terrigenous organic matter (TOM) are composed predominantly of woody material (the gas-prone Type-III kerogen). Similar results were obtained during the Rock-Eval pyrolysis. Moreover, the GC-MS analysis of extracts indicated the additional source of OM, namely planktonic organic matter (POM) with oil-prone kerogen Type-I or II. This OM is in some cases high thermally mature and could potentially has allochthonous origin. The n-alkane, saturated and aromatic biomarker data revealed deposition of this POM in anoxic deltaic or close-shore sedimentary environments whereas the redeposited coal clasts were probably originally deposited in coal swamps as were the Upper Silesian bituminous coals.

The influence of redeposition on the anthracological records from the Moravian Karst caves (Czech Republic, Central Europe)

The study focuses on some methodological problems associated with the research of cave sites. A large amount of anthracological material came from the context of the layers with archaeological material from the Pod hradem Cave (Moravian Karst, Czech Republic). Some samples were determined as Taxus, which in this context would be among the first evidence of yew in the Middle Pleistocene. However, their dating showed significant secondary redepositions. Similar redepositions of material were repeatedly found in the dating of material from the Kůlna Cave (Moravian Karst, Czech Republic). Here, too, in certain parts of the cave, there was secondary redeposited archaeological material in seemingly intact sediments. Both caves were inhabited – Kůlna Cave from MIS 8 to MIS 2, Pod hradem Cave – from MIS 3e to MIS 2. At the same time, intensive post-sedimentation processes took place in both caves, accompanied by the activities of large carnivores inhabiting these caves alternately with humans. The last important factor influencing stratigraphy was the archaeological excavations at the end of the 19th and the beginning of the 20th century.

New Type of Fluidizate-Explosive Rock in Sedimentary Strata (Torgashino Limestone Deposit, Eastern Sayan Mountains, Russia)

The paper provides the results of comprehensive studies of bodies composed of different fluidolite types (psephitic, argillizite) and hydrothermalites found in the carbonate stratum of the Torgashino suite (Eastern Sayan Mountains, Russia). These rocks are the result of post-sedimentation processes imposed on limestones. Argillizites in the carbonate stratum are referred to a new type of fluidizate-explosive rock. Their low-temperature hydrothermal origin and association with the Later Ordovician tectono-magmatic activation of the area have been identified.

Influence of formation conditions on reservoir thickness and reservoir properties

Authors of the article identified the influence of sedimentation conditions on reservoir thickness and the patterns of change in reservoir properties of superviscous oil field from the following three zones of the sandstone sequence of the Sheshminsky horizon: Northern, Southern and Central identified by PJSC Tatneft and prepared for initial development. The following relationships have been investigated: open porosity relation with bitumen content (by weight and by volume), open porosity relation with carbonate content, open porosity relation with bulk density, carbonate content relation with bulk density, bitumen content (by weight and by volume) relation with carbonate content, and also bitumen content relation with their depth. The revealed patterns of changes in reservoir properties and bitumen content within the sandstone sequence can be the result of not only changing conditions of sedimentation, but also the result of post-sedimentation processes resulting in calcitization or redistribution of carbonate cement in the rock under the influence of aggressive products (oxidation, biodegradation) of oil deposits destruction.

238U/235U isotopic ratio as redox conditions marker in ediacarian paleobasin: section in Chaya river, Baikal-Patom highland, south of middle Siberia

This article is devoted to a study of variations in the U isotopic composition (238U/235U) in the section of clas- tic-carbonate Ediacaran sediments exposed along the Chaya River in the southern part of Central Siberia (Russia). Measurements of 238U/235U in the rocks were performed using a high-precision (±0.07%o, 2SD) MC-ICP- MS with a 233U-236U double isotope spike. The total variation range of S238U in the studied carbonate rocks was -0.91 to -0.01%. Extremely low values of S238U (-0.91%, -0.9%, and -0.84%), which were found in a number of samples from the lower part of the section, are interpreted as the result of postsedimentation processes affecting the rocks. In the overlying sediments, the range of S238U variations is smaller from -0.49 to -0.01%. Here, regular “weighting” of the U isotopic composition observed upwards through the section indicates an increase in the reduction conditions at this time (about 550 Ma) in the paleobasin. This conclusion is consistent with the elevated concentrations of U, Mo, and V in the Late Ediacaran sedimentary rocks of the region studied.

Tellurium-bearing minerals in clastic ores of Ybileynoe massive sulfide deposit (South Urals)

At the well preserved Yubileynoe VMS deposit (South Urals), sulfide breccias and turbidites contain abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, calaverite as well as phases of intermediate solid solution tellurobismuthite – rucklidgeite. There is three generation of tellurides were highlighted: 1) primary hydrothermal tellurides in the fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; 2) authigenic tellurides in pseudomorphic chalcopyrite and veins of chalcopyrite after fragments of colloform and granular pyrite; 3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. In sulfide turbidites and gravelites with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts, primary hydrothermal and authigenic tellurides are less common. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, which peripheral parts contain inclusions of epigenetic tellurides. It is assumed that the source of tellurium for authigenic tellurides were fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during post-sedimentation processes. The main concentrators of tellurium in clastic ores are pseudomorphic chalcopyrite, which inherits high contents of Te, Bi, Au, Ag, Co, Ni, As from the substituted colloform pyrite, and varieties of granular pyrite, containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite and hessite (Ag, Te).

Manifestations of post-sedimentation processes in the Lower Cretaceous sediments of Bolshekhetskaya depression (Western Siberia)

Оbject.The article presents the results of studies of secondary mineral formation in the lower Cretaceous sediments of the Bolshekhetskaya depression, which contain highly promising oil and gas deposits, with established industrial performance at Pyakyakhinskoye, Khalmerpayutinskoye and South-Messoyakhskoye fields. The objects under consideration are located in the most submerged part of the Nadym-Taz syneclise in the zone, where the Taz and Urengoy facies regions meet.Materials and methods.Main types of postsedimentary changes of reservoir rocks selected on the basis of study of core material Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms. Petrography and Mineralogy of the rocks under consideration were studied on the basis of stage analysis using optical and electron microscopy, and X-ray diffraction study at the Center of core and reservoir fluids research of “LUKOIL-Engineering’s KogalymNIPIneft branch In Tyumen” (Kogalym). Determination of the mineral type of zeolite was performed by X-ray phase analysis at the Institute of Geology and Geochemistry UrO RAS (Ekaterinburg).Resuts.It was found that for rocks Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms characteristic a diverse range of secondary minerals and structures, evidence of the background stage catagenesis and the superimposed processes. The most important among them is the regeneration of quartz, the transformation of feldspar, violation of the crystal structure of biotite, the formation of various clay minerals, crystallization of zeolites and calcite.Conclusions.Studies show that the upper part of the section of the lower Cretaceous deposits of Bolshekhetskaya depression corresponds to the area of the middle catagenesis (gradation MK2), the bottom – changed to the stage of deep catagenesis (gradation MK3). In this case, the epigenetic process proceeded unevenly, pulsation, due to changing tectonic conditions. Particular attention is paid to the origin of zeolites, which is still debatable. It is assumed that their formation is associated with the transformation of “camouflage pyroclastic” in particular, feldspar clastics.

Tellurium-Bearing Mineralization in Clastic Ores at the Yubileynoe Copper Massive Sulfide Deposit (Southern Urals)

At the well-preserved Yubileynoe VMS deposit (Southern Urals), sulfide breccias and turbidites host abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, and calaverite, as well as phases of the intermediate tellurobismuthite → rucklidgeite solid solution. Three telluride generations were highlighted: (1) primary hydrothermal tellurides in fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; (2) authigenic tellurides in pseudomorphic chalcopyrite and chalcopyrite veins after fragments of colloform and granular pyrite; and (3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. Primary hydrothermal and authigenic tellurides are less common in sulfide turbidites and gritstones with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, whose peripheral parts contain inclusions of epigenetic tellurides. It is assumed that Te for authigenic tellurides originated from fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during the postsedimentation processes. The main Te concentrators in clastic ores include pseudomorphic chalcopyrite, which inherits high Te, Bi, Au, Ag, Co, Ni, and As contents from the substituted colloform pyrite, and varieties of granular pyrite containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite, and hessite (Ag, Te).