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Constructing a reservoir simulation model requires an accurate definition of saturation functions, including capillary pressure and relative permeability data. Usually, these saturation functions are available only for a limited number of samples. Assigning saturation functions to the simulation model requires finding a clear relationship between them and a 3D predictable property of grid cells. Different indices are usually evaluated to describe such a relationship. It was recently shown that each petrophysical dynamic rock type should form similar True Effective Mobility (TEM) curves. In this study, TEM-function was used to evaluate the reliability and performance of different rock typing indices in defining dynamic rock types. FZI, FZIM, MFZI, and FZI∗ (FZI-star) indices were considered and tested on a collection of laboratory-derived core-flooding data from an Iranian carbonate reservoir. Results showed that FZI-star had a better performance than FZI, MFZI, and FZIM.

Resource modeling plays a crucial role in raw material quality management for cement manufacturing. Research has shown that geological uncertainty in resource modeling is inevitable and results in risk to future extraction planning and operations of the cement plant. This study aims to assess the geological uncertainty and associated risk in modeling a cement raw material deposit in southern Vietnam. For this deposit, soil, clay, laterite, and limestone are the four primary rock types, controlling the occurrence and spatial distribution of chemical grades. In this study, hierarchical simulation method was used to evaluate the uncertainty. Rock types were first simulated, and the chemical grades conditioning to the rock types were then generated. The results demonstrated the capability of the hierarchical simulation approach to incorporate the uncertainty of rock types in resource modeling and to allow evaluating the risks in providing the desired raw material for the cement plant in the form of grade-tonnage curves.

Special core analysis (SCAL) measurements play a noteworthy role in reservoir engineering. Due to the time-consuming and costly character of these measurements, routine core analysis (RCAL) data should be inspected thoroughly to select a representative subset of samples for SCAL. There are no comprehensive guidelines on how representative samples should be selected. In this study, a new framework is presented for selection of representative samples for SCAL. The foundation of this framework is using methods of PSRTI, FZI∗ (FZI-star) and TEM-function for the early estimation of petrophysical static, dynamic, and pseudo-static rock types at RCAL stage. The global hydraulic element (GHE) approach is benefitted and a FZI∗-based GHE method (i.e., GHE∗) is presented for partitioning data. The framework takes into consideration different laboratory, reservoir engineering, geological, petrophysical and statistical factors. A carbonate reservoir case is presented to support our methodology. We also show that the current forms of Lorenz and Stratigraphic Modified Lorenz Plots in reservoir engineering are not appropriate, and present new forms of them.

The paper presents petrochemical, geochemical, and mineralogical data on rocks of the phoscorite–carbonatite complex in the Kovdor alkaline–ultramafic massif, Kola Peninsula, Russia. In contrast to what is usually thought, trace elements were determined to be concentrated not in the carbonatites themselves but in the related phoscorites. The paper presents data on the evolution of the compositions and zoning of minerals in successive generations of both rock types as a result of the fractional crystallization of their parental magmas, and data on general trends in the concentrations of trace elements. The Fe-rich phosphate–carbonate melt seems to have separated from the primitive alkaline–ultramafic silicate melt during its advanced differentiation. The Fe-rich phosphate–carbonate magma was parental for the phoscorite–carbonatite complex. The possibility of its splitting into immiscible Fe-rich phosphate and carbonatite melts is discussed.

The present study evaluates the performance of PNN models for porosity prediction using seismic attributes. Four seismic datasets and more than 20 wells from different sedimentary basins located in Libya, Iraq, Egypt and USA are employed to characterize the effective attributes for porosity prediction. Verification and testing error analysis is adopted for evaluating the prediction performance. Results indicated that the porosity prediction models are primarily dependent to the propagation related attributes with frequency attributes as the most effective parameters in porosity prediction. In addition, the data quality and processing history strongly control the prediction model performance with relatively limited effects to dataset dimensionality (2D versus 3D) and the number of wells utilized in model construction. Such results are important to better understand and evaluate the performance of PNN porosity prediction models using various seismic attributes. Keywords: Porosity prediction, Seismic attributes, PNN, Al Ghani field, Sooner field, Kifl field, Baltim field

Rock typing is an important tool in evaluation and performance prediction of reservoirs. Different techniques such as flow zone indicator (FZI), FZI* and Winland methods are used to categorize reservoir rocks into distinct rock types. Generally, these methods are applied to petrophysical data that are measured at a pressure other than reservoir pressure. Since the pressure changes the pore structure of rock, the effect of overburden pressure on rock typing should be considered. In this study, porosity and permeability of 113 core samples were measured at five different pressures. To investigate the effect of pressure on determination of rock types, FZI, FZI* and Winland methods were applied. Results indicated that although most of the samples remain in the same rock type when pressure changes, some of them show different trends. These are related to the mineralogy and changes in pore system of the samples due to pressure change. Additionally, the number of rock types increases with increasing pressure. Furthermore, the effect of overburden pressure on determination of rock types is more clearly observed in the Winland and FZI* methods. Also, results revealed that a more precise reservoir dynamic simulation can be obtained by considering the reservoir rock typing process at reservoir conditions.

Evaporites, such as salt and potash, pose unique problems to ground-support designs that are not encountered in other rock types. Evaporites are subject to continual creep and no amount of ground support can successfully arrest this process. Common ground-support techniques that are useful for most rock types may reduce the effective life of bolts in evaporite mines and create unseen hazards. A different approach to ground support must be applied to provide long-term support in areas where high creep rates are present. The goal of effective ground-support designs in these situations is not to contain and prevent the rock from moving; rather, the ground-support design must be able to move along with the rock and contain any fully detached slabs until additional remediation measures can be undertaken. The most appropriate ground-support designs will consider the expected movement of the rock and the duration that the area needs to remain accessible. Keywords: Ground support, Ground control, Rock mechanics, And salt mechanics

There was extensive Permian to Triassic magmatism in Hainan Island, southern part of the South China Block (SCB), which began earlier and exhibits different rock types and geochemical characteristics compared to the Indosinian magmatism in the hinterland of the SCB. Two stages of magmatism have been identified in central Hainan Island in this study. The first-stage magmatism (253–262 Ma) is characterized by strongly deformed granites. These gneissic granites exhibit SiO2 (64.0–69.8 wt%), MgO (0.97–1.60 wt%), Fe2O3T (2.68–6.78 wt%), A/CNK (most

Classification of rock types using geochemical variables is widely used in geosciences, but most standard classification methods are restricted to the simultaneous use of two or three variables at a time. Machine learning-based methods allow for a multivariate approach to classification problems, potentially increasing classification success rates. Here a series of multivariate machine learning classification algorithms, together with different sets of lithogeochemistry-derived variables, are tested on samples collected at the Lalor Zn-Cu-Au volcanogenic massive sulphide deposit, to discriminate volcanic units and alteration types. Support Vector Machine and Ensemble method algorithms give the best performance on both classification exercises. Untransformed chemical element concentrations with high classification power are the best-performing variables. Classification success rates are equal or better than those obtained using standard classification methods and are satisfactory enough for the use of the resulting predictions for 2D and 3D modelling of geological units.

Metasomatism occurs when fluid interacts with rock to add, or remove, its chemical constituents; these processes form mineral deposits where economic element(s) are concentrated into small volumes of rock. It can be difficult, or impossible, to visually determine original rock types for samples that are significantly altered, e.g., when rocks have experienced texturally destructive metasomatism or deformation. A typical solution using chemical data involves the separation and labelling of chemically distinct rocks using discrimination diagrams. However, such approaches can be subjective, and manual sample-by-sample consideration of large mining or exploration databases is untenable. Here we present an example workflow to facilitate relating rocks with similar origins but differing geological histories. We employ a combination of unsupervised and supervised machine learning algorithms to automate classification tasks typically undertaken manually by a geologist with domain expertise. In this study, data are first normalised and then clustered into natural groupings that represent protolith lithologies or rock-type subunits. These clusters are then used to inform a classification algorithm that assigns protolith equivalent labels to samples of altered rocks. Applied to problems involving large chemical datasets, machine learning provides objectivity, reproducibility and rapidity; useful advantages as compared to geostatistical domaining methods that involve manual determination and selection of geochemically similar regions. We utilise k-means ++ unsupervised clustering to create objective and reproducible groupings of data points, with many geochemical variables considered simultaneously. Subsequently, Random Forests supervised classification is used to label samples while accommodating interactions and/or correlations between data points. We present a case study from the Minto Cu-Au-Ag mine, Whitehorse, Yukon, Canada. Interpretation of multi-element geochemical data using the approach that we have outlined here allows reconstruction of protolith geometry and an understanding of how rock type may have influenced later partitioning of hydrothermal fluids and ductile deformation.

The inherent nonuniqueness in modeling magnetic data can be partly reduced by adding prior information, either as mathematical constructs or simply as bounds on magnetization obtained from laboratory measurements. If a good prior model can be used as a reference model, then the quality of estimated models through an inverse approach can be greatly improved. But even though data on magnetic properties of rocks might exist, their distribution may often be quite irregular on local and regional scales, so that it is difficult to define representative classes of rock types suitable for constraining geophysical models of magnetization. We have developed a new way of constructing a reference model that varies only laterally and is confined to the part of the terrain that lies above the lowest topography in the area. To obtain this model, several estimated 2D magnetization distributions were constructed by data inversion as a function of the iteration number. Then, a suitable 2D model of the magnetization in the topography was chosen as a starting point for constructing a 3D reference model by modifying it with a vertical decay such that its average source depth was the same for all horizontal positions. The average source depth of the reference model was chosen to satisfy the average source depth obtained from analyzing the radial power spectrum of the area studied. Finally, the measured magnetic data were inverted in three dimensions using the given reference model. For a selected reference model, shallow structures indicated a better overall correlation with large remanent magnetizations measured on rock samples from the area. Throughout the entire model, the direction of magnetization was allowed to vary freely. We found that the Euclidean norm of the estimated model was reduced compared with the case where the magnetization direction was fixed.

Tectonically young, orogenic settings are commonly the sites of post-collisional silica-rich ultrapotassic magmas with extreme K2O-contents of up to 9 wt% and K2O/Na2O > 2. Many experimental studies investigating the generation of these melts have concentrated on melting of homogenous phlogopite bearing peridotites, whereas geochemical signatures indicate the involvement of at least two types of source rocks: ultra-depleted and K and trace elements-enriched ones. We report the results of melting experiments at 1–2 GPa of mixed glimmerite and harzburgite, in which these rock types make up two halves each capsule. Melting begins in the glimmerite, and its metasomatic effects on the harzburgite are apparent at 1100 °C even before melt pools are visible. The first melts are Na-rich, seen in zoning of olivines and as growth of clinopyroxene in the harzburgite, but change at higher degrees of melting to produce a typical lamproite-like melt with K2O > 10 wt%. A major advantage of this study is the preservation of distinct melts in different parts of the capsule, which reflect a process of dynamic metasomatism: within the harzburgite matrix, the infiltrating melt derived from melting of the glimmerite changes consistently with the distance of travel through the harzburgite, enabling quantification of the metasomatic effects as an increase in SiO2 and K2O. This results principally from assimilation of orthopyroxene, which increases the Ol/Opx ratio of the residual harzburgite. The effects of quench olivine growth are recognizable and can be quantified due to a step-change in composition at the glimmerite/harzburgite border: the large total surface area of olivine and small melt fraction mean that the amount of quench olivine is high within the harzburgite, but negligible in the almost completely molten glimmerite. Melts of the glimmerite contain up to 8–10 wt% K2O and 53 wt% SiO2, which increase to 55–56 wt% after interaction with the harzburgite. Mediterranean lamproites resemble melts of glimmerite, whereas melts that have interacted with harzburgite are more similar to less potassic, but more SiO2-rich shoshonites of the Mediterranean region.

Garnet could be the ultimate petrochronometer. Not only can you date it directly (with an accuracy and precision that may surprise some), but it is also a common rock-forming and porphyroblast-forming mineral, with wide ranging—yet thermodynamically well understood—solid solution that provides direct and quantitative petrologic context. While accessory phase petrochronology is based largely upon establishing links to the growth or breakdown of key rock-forming pressure–temperature–composition ( P–T–X ) indicators (e.g., Rubatto 2002; Williams et al. 2007), garnet is one of those key indicator minerals. Garnet occurs in a great variety of rock types (see Baxter et al. 2013) and is frequently zoned (texturally, chemically) meaning that it contains more than just a snapshot of metamorphic conditions, but rather a semi-continuous history of evolving tectonometamorphic conditions during its often prolonged growth. In this way, garnet and its growth zonation have been likened to dendrochronology: garnet as the tree rings of evolving tectonometamorphic conditions (e.g., Pollington and Baxter 2010). In some ways, the dream of ‘petrochronology’ all started with garnet (Fig. 1). When Atherton and Edmunds (1965) or Hollister (1966) recognized the chemical zonation in garnet, when Rosenfeld (1968) noted the spiral ‘snowball’ of inclusions in rotated garnet, or when Tracy et al. (1976) drew the first 2-D map of garnet chemical zonation, illuminating those ‘tree-rings’ for the first time, they could only imagine what is now a reality decades later—direct zoned garnet geochronology of those concentric rings of growth. Geoscientists soon thereafter attempted the first garnet geochronology (van Breemen and Hawkesworth 1980), though several factors severely limited the development and wider-spread use of garnet geochronology from that point. These factors included 1) contamination of garnet by micro-mineral inclusions, 2) analytical limitations of small sample size, 3) the requirement of anchoring a garnet age analysis with another point on an isochron, and …

Some faults are considered strong because their strength is consistent with the Coulomb criterion under Byerlee's friction, 0.6 μ 0.85 . In marked contrast, numerous studies have documented significant fault weakening induced by fluid-assisted reaction softening that generally takes place during the long-term evolution of the fault. Reaction softening promotes the replacement of strong minerals with phyllosilicates. Phyllosilicate development within foliated and interconnected fault networks has been documented at different crustal depths, in different tectonic regimes and from a great variety of rock types, nominating fluid-assisted reaction softening as a general weakening mechanism within the seismogenic crust. This weakening originates at the grain-scale and is transmitted to the entire fault zone via the interconnectivity of the phyllosilicate-rich zones resulting in a friction as low as 0.1 μ 0.3 . Collectively, geological data and results from laboratory experiments provide strong supporting evidence for structural and frictional heterogeneities within crustal faults. In these structures, creep along weak and rate-strengthening fault patches can promote earthquake nucleation within adjacent strong and locked, rate-weakening portions. Some new frontiers on this research topic regard: 1) when and how a seismic rupture nucleating within a strong patch might propagate within a weak velocity strengthening fault portion, and 2) if creep and slow slip can be accurately detected within the earthquake preparatory phase and therefore represent a reliable earthquake precursor.

The paper presents data on the specifics of the distributions of chemical elements in natural waters of the Kola North depending on the landscape–geochemical characteristics of the water catchment areas and aerotechnogenic pollution. The territory is subdivided into seven zones with different dominant rock types and typical landscapes. Lakes in the Kola region generally contain elevated concentrations of Cu, Ni, Co, Cr, V, Mo, U, Sb, Bi, Al, Fe, Mn, Sr, Li, Rb, Pb, Zn, Cd, La, and Ce. The waters of lakes in the influence zones of Cu–Ni mines are enriched in La, Ce, Sm, Gd, Pr, and Nd. In waterlogged landscapes, waters are enriched in certain trace elements because of their migration with humic acids. Technogenic acidic precipitation is proved to result in leaching of several elements, first of all Cd, Zn, and As (as well as other elements contained in rocks composing the water catchment areas) and their transfer into the waters.

Geological modeling is a useful tool for host rock reconstruction in volcanogenic massive sulfide (VMS) deposits. In this paper, we have proposed two rock type models for Nohkouhi copper deposit, which is a siliciclastic felsic volcanogenic massive sulfide in Central Iran zone. In the deposit, copper mineralization is hosted by different copper grade rocks consisting of Black shale and Rhyodacite. Moreover, in the Black shale, the copper grade distribution directly corresponds to the Rhyodacite. Geochemical factors of the rock types distinguished using ICA. Scores of the IC1 via Scores of the IC2 indicated the best discrimination between the Black shale and Rhyodacite. Our manually constructed class boundary provided a bivariate discriminant line that can be used to determine the rock types. Scores of the ICs are simulated using sequential Gaussian simulation (SGS). The discriminant line is used to classify each node of the grid to the rock type for each pair realization. Also, sequential indicator simulation (SIS) is applied to the Black shale and Rhyodacite on account of their wide range of geometries and assumed deterministic geological model. In order to model the deposit, we have compared two methods comprising direct simulation of rock type (using sequential indicator simulation) and indirect simulation of rock type (using independent component analysis). The experimental results indicated that direct simulation, could be employed for both resource evaluation and knowledge of the geological model. Besides, the indirect simulation produces a model which cannot be used for resource evaluation stage; however, it is helpful with respect to the basic understanding of the geology of the deposit. Our two models showed 96% agreement with each other. Also, ICA chemically presented a key relations between Black shale and Rhyodacite.

Numerous studies on active mountain ranges have demonstrated the interaction between tectonics and climate in shaping topography. Here we explore how variations in rock types have affected the topographic development of the Pyrenees since cessation of orogenesis ca. 20 Ma. Our study is based on a multidisciplinary approach and integrates topographic analyses, rock strength measurements and thermal modelling of low-temperature thermochronological data published across the Central Pyrenees. Results indicate a strong influence of rock strength in determining the post-orogenic morphology of the Pyrenees. We observe a correlation between rock strength and the normalized channel steepness index ( k s n ) of the different lithologies. Moreover, the highest topography is dominated by the Variscan plutonic massifs which have highest rock strength. Consequently, the drainage divide appears to track the position of these massifs. Abrupt deceleration of exhumation recorded in inverse modelling of low-temperature thermochronologic data suggests that the exhumation of the Variscan massifs also played role in lowering in erosion rates over the massifs during orogenesis.

Pressure-solution creep is one of the most common crustal deformation mechanisms, inducing changes in the porosity and permeability of rocks. For a variety of rock types undergoing pressure solution, it has been shown that the presence of phyllosilicates may significantly enhance the rate of the pressure-solution process. In this experimental investigation, we present 4-dimensional (three dimensions + time) X-ray microtomographic data that contrast deformation by pressure-solution of a pure NaCl aggregate with that of a mixture of NaCl and biotite. The results show that for mixed samples (NaCl+biotite), phyllosilicates induce a marked reduction in porosity and pore connectivity and contribute to an increase in the local strain rates by an order of magnitude over pure NaCl samples. At the same time, phyllosilicates do not induce strain localization in the sample. We discuss various possible explanations for these observations including a possible positive feedback between the porosity distribution and pressure solution. Our study yields novel insights into the local effects of phyllosilicates during pressure-solution creep and provides full 4-dimensional imaging and characterization of the coupled evolution of porosity and pore connectivity over previously unprecedented experimental time scales.

This paper presents results of the study of norite complex from the Vestfold Hills (East Antarctica) containing a low-sulfide type of mineralization. The ore mineralization occurs in specific rock types and along the contact of norites the host rocks. Three mineralization types: Fe–Ni–Cu sulfide, oxide, and PGE-bearing are known. PGE mineralization is represented by palladium–bismuth tellurides of the michenerite–merenskyite series. A model of ore-formation succession and a concept of the origin of low-sulfide PGE mineralization by means of crystallization and subsequent evolution of monosulfide and intermediate solid solutions have been developed.

In this paper, the southwestern Fujian metallogenic belt, one of the important Fe polymetallic belts in southern China, was chosen as a case study area to evaluate the uncertainty due to missing evidence in mineral prospectivity mapping. Four geological features were considered important for mineral prospectivity mapping based on the geological model for skarn deposits in the belt: (1) the Yanshanian granitic intrusions, because they provided energy, fluids, and part of the metal budget; (2) faults, because they served as pathways for hydrothermal fluids; (3) the Carboniferous–Permian carbonate sequences, because they supplied part of the metal budget and served as host rocks for ore deposition; and (4) geochemical anomalies, because they indicate presence of skarn-type alteration and mineralization. Four separate predictive evidence layers depicting each the above geological features were extracted from relevant geoscience data and were integrated using a modified fuzzy weights-of-evidence model, which retains the advantages of both fuzzy weights-of-evidence and logistic regression modeling. The results show that most of the known Fe deposits occur in or near, and thus have strong correlation with, areas of high posterior probabilities, as indicated by the delineated prospective areas that occupy only 4.6% of the studied region but contain 88.5% of the total number of known Fe deposits. Different combinations of predictive evidence layers were used to examine prediction uncertainty related to missing evidence. Plots of accumulative number of Fe deposits versus accumulative prospective areas show that the order of the most to the least important evidence of mineral prospectivity in the studied region is: favorable rock types > geochemical anomalies > intrusive rocks > faults. Results of blind testing the prospectivity models indicate that the geological model of Fe mineralization in the belt is suitable for predicting exploration target areas for skarn-type Fe deposits, and suggest that the highest risk in follow-up exploration is related to sequences of carbonates in the Carboniferous–Permian formations that were likely either not mapped or not represented at the present regional scale of mapping.

Supergene metal deposits form when common rock types or deeply buried primary ore bodies are exposed at or near the Earth's surface and undergo oxidation, dissolution and reconcentration of the metals. Supergene metal deposits are economically interesting because of their accessibility for extraction and increased grades. Scientifically they are attractive because of their mineralogical diversity and what they reveal about surficial history. Apart from supplying mankind's need for metals, supergene metal deposits provide clues about our past climate and offer an unparalleled opportunity to explore the long-term corrosion behavior of natural and man-made materials and their environmental impact.

The Beiya gold–polymetallic orefield, with gold reserves of 305 t, is one of the most representative porphyry-skarn orefields in the Jinshajiang–Ailaoshan Cu–Au ore belt within the Sanjiang region of southwest China. The orefield contains seven deposits: the Wandongshan, Hongnitang, Dashadi, Bijiashan, Weiganpo, Matouwan, and Bailiancun deposits. In this paper we report on the geochemistry and geochronology of porphyries associated with mineralization from the seven deposits. The results show that all the porphyries have similar geochemistry, with high alkalinity, high contents of SiO2, Al2O3, K2O, and Sr, high K2O/Na2O ratios, low MgO, Y, and Yb contents, enrichments in Ba, K, and Pb, depletions in P, Ti, Nb, and Ta, and non-evident to weak Eu depletions (δEu = 0.42–0.99). In the SiO2 vs. Th/Ce diagram, the porphyry samples are distributed in the area of thickened lower crust, and in the Sr/Y vs. Y and La/Yb vs. Yb diagrams, the porphyries broadly followed the batch-melting trend of amphibolite containing up to 10% garnet. LA-MC-ICP-MS zircon U–Pb dating analysis suggests that the porphyries were emplaced between 34.62 ± 0.25 and 36.72 ± 0.25 Ma. They were coeval with lamprophyres (34 to 36 Ma) in the Beiya area and with potassic–ultrapotassic intrusive rocks (40 to 35 Ma) within the Jinshajiang–Ailaoshan magmatic belt, indicating possible genetic relation between these rock types. We suggest that the porphyries in the Beiya gold–polymetallic orefield were derived from the partial melting of a K-rich mafic source in the thickened lower crust, with the melting triggered by asthenospheric upwelling following the removal of lower lithospheric mantle.

We performed a joint analysis of SHRIMP II U-Pb ages (68 measurements for 5 rock types) and trace and rare-earth element compositions of zircons (41 determinations made in the same points that were utilized for measurement of U-Pb isotope ratios) from the complex Orekhovo-Pavlograd shear zone of the Ukrainian Shield. It was determined that this zone is composed of rocks of different age: 3.5, 3.4, 2.8, and 2.0 Ga. The main stage of structural-metamorphic reworking took place 2.0 Ga and lasted for over 30 Ma. It was established that fluid reworking of zircons was accompanied by an increase of LREE content and decrease of Ce anomaly. The preservation of U-Pb system in some zircons with high LREE contents may be explained by their solid state transformation.

Triaxial compression tests were carried out on Shikotsu welded tuff, Kimachi sandstone, and Inada granite under confining pressures of 1–15 MPa at 295 and 353 K. The permeability of the tuff declined monotonically with axial compression. The post-compression permeability became smaller than that before axial compression. The permeability of Kimachi sandstone and Inada granite declined at first, then began to increase before the peak load, and showed values that were almost constant in the residual strength state. The post-compression permeability of Kimachi sandstone was higher than that before axial compression under low confining pressures, but lower under higher confining pressures. On the other hand, the permeability of Inada granite was higher than that before axial compression regardless of the confining pressure values. For the all rock types, the post-compression permeability at 353 K was lower than at 295 K and the influence of the confining pressure was less at 353 K than at 295 K. The above temperature effects were observed apparently for Inada granite, only the latter effect was apparent for Shikotsu welded tuff, and they were not so obvious for Kimachi sandstone. The mechanisms causing the variation in rock permeability and sealability of underground openings were discussed.

Based on in-mine instrumentation and theoretical analysis of the unsymmetrical large-deformation that occurred in the roadway after excavation, Differential Floor Heave (DFH) was found to be the main reason for roadway failure. It needs to be pointed out that the specific roadway was driven in inclined rock strata. In addition, the factors that contribute to the occurrence of DFH are discussed in detail. It is believed that DFH is triggered by the unsymmetrical stress distribution in the floor and the different rock types encountered near the two floor corners. Hence, DFH control should be focused on the left floor corner where shearing failure occurs initially and the left floor surface where tensile failure is more severe. The proposed DFH control strategies include unsymmetrical grouting for the whole roadway, re-design of the roof and ribs support, reinforcement of the weak zones, and release of the concentrated stress in the earlier stage. Meanwhile, it is recommended that in the later stage, both bolts and cable bolts with higher strength and the backfilling technique using the coal measure rocks and concrete should be employed in the reversed-arch floor. The field instrumentation results, after using the proposed control strategies, indicate that large deformation in a DFH roadway has been successfully controlled. Keywords: Deep roadway, Inclined strata, Differential Floor Heave (DFH), Unsymmetrical deformation, Two stage control strategies

An earthquake dataset consisting of 327 records from 67 earthquakes is used to study the frequency‐dependent amplitude decay of seismic coda waves in the Kumaon Himalayas, India. Coda amplitude decays with time t are measured by empirical t − α dependences, with exponent α being variable regionally with frequencies and lapse times. The results show that α varies from 1 to 3, with an average of about 1.93. The lapse‐time dependence of α is noticeable but weak, and no significant azimuthal dependence of α is obtained. Significant regional variations of α are found, ranging from α ≈2.1 for the Lesser Himalaya to α ≈1.76 for the Greater Himalaya. These variations correlate with the geology of the region and crustal structure. The values of α are mostly frequency independent, indicating low intrinsic attenuation within the crust. When interpreted according to the conventional coda‐ Q ( Q c ) model, these values of α lead to Q c ≈78 f 1.06 in the Kumaon Himalaya, Q c ≈90 f 1.09 in the Kumaon Lesser Himalaya, and Q c ≈90 f 0.92 in the Kumaon Greater Himalaya. A frequency‐dependent α is found within a localized area, giving an estimate of near‐surface Q ≈200. Three general conclusions of this study may be significant for coda studies in other areas. First, the values of α are variable regionally, whereas its average level is remarkably constant and correlates with rock types and upper‐crustal structure. Second, the traditionally assumed value of α =1 is much lower than the actual spreading rates, which shows that the coda cannot be viewed as body waves scattered within a uniform crust. Using the value of α =1 causes a systematic underestimation of coda amplitude decays in the data. Third, the dependence of α on frequency is relatively weak and occurs in localized areas. Combined with an underestimated α , this weak frequency dependence may cause biases in the estimation of secondary parameters, such as coda Q .

Sulfides are among the most important petrogenetic agents in magmatic systems. They are ubiquitous in most upper-mantle rock types, common as inclusions in diamonds and they host significant amounts of geochemically and economically important chalcophile (‘sulfur-loving’) elements, such as Cu, Ni, Pb, In, Au and the platinum-group elements. Despite their low abundance (<< 1% of the bulk rock), residual sulfides have a disproportionate control over the chalcophile element budget in upper mantle lithologies, as well as that of melts derived from the Earth's mantle.

Shale is one of the most common rock types, with a rich and complex variety of failure structures in the Earth’s continental crust. In this paper, a synopsis of these structures including joints, pressure-solution seams and cleavages, faults, and shear bands is presented. First, two main categories, sharp and diffuse structures, each of which has subclasses based on its displacement discontinuity type including shear, compaction, and dilation are defined. Then, natural field examples are provided for each class as well as complex structural assemblages that include more than one type of failure-mode structures. Finally, the significances of these assemblages in terms of how older structures may influence later natural and man-made fractures and how they may interact in terms of fluid and gas flow are briefly discussed.

The North China Craton (NCC) is characterized by major ∼2.5 Ga tectono-thermal events and is thus different from many other cratons worldwide where ∼2.7 Ga events are well developed. However, whole-rock Nd and Hf-in-zircon isotopic compositions of ∼2.5 Ga crustally derived granitoids reveal that they mainly formed through reworking of late Mesoarchean to early Neoarchean continental material. We review the spatial distribution, rock types, geochemical and Nd–Hf isotopic compositions of ∼2.7 Ga granitiods that are widely identified in the NCC, including eastern Shandong, western Shandong, Huoqiu, Hengshan, Fuping, Zanhuang, Zhongtiao and Wuchuan. These granitoids are mainly tonalitic in composition and frequently underwent strong metamorphism, deformation and anatexis. They show large variations in SiO 2 , total FeO, MgO and CaO, and can be subdivided into two types in terms of their REE patterns. More importantly, whole-rock Nd and Hf-in-zircon isotopic compositions indicate that the strong ∼2.7 Ga tectono-thermal event mainly involved juvenile additions to the continental crust. The early Neoarchean was the most important period for rapid production of new continental crust in the NCC. The main difference of the NCC from many other cratons worldwide is a strong and widespread superimposed tectono-thermal event at ∼2.5 Ga that stabilized the cratonic assemblage.

We investigate the evolution of wear and friction along experimental faults composed of solid rock blocks. This evolution is analyzed through shear experiments along five rock types, and the experiments were conducted in a rotary apparatus at slip velocities of 0.002–0.97 m/s, slip distances from a few millimeters to tens of meters, and normal stress of 0.25–6.9 MPa. The wear and friction measurements and fault surface observations revealed three evolution phases: A) An initial stage (slip distances

This paper presents the results of geological and petrophysical research carried out on Popov Island by the Pacific Oceanological Institute of the Far East Branch of the Russian academy of Sciences during 2003–2009. As a result, 7 types of rocks were identified. Their density and magnetic susceptibility have been determined. It was established that the rock types are clearly differentiated with respect to their physical parameters. The identified relationship allows one to use these physical properties, first of all, for the geological interpretation of the gravity and hydromagnetic survey carried out in the surrounding water area of Peter the Great Bay and, secondly, as an additional indicator for igneous rock typification on other islands of the region. Such comprehensive and integrated research was carried out for the first time in this area. The results obtained are important for solving the problem of the structural, compositional, and genetic relationships between the terrestrial and marine structures at the junction zone between the Japanese Basin and the adjacent continent.

Records of past exploration in open-file mineral exploration reports are an important source of information for mineral explorers. These reports document existing geological knowledge that may be relevant to modelling ore forming processes in a particular area of interest. This paper presents the development of GeoDocA, a geological document analysis system, that applies automated text analysis techniques with the specific aim of assisting geologists in browsing of and searching for documents based on relevant geological contents within a large repository of documents. GeoDocA analysed 25,419 exploration reports and using a customised set of keywords pertaining to broad categories such as mineral occurrences, rock types, alteration types, and geological time. An interactive user interface was developed to facilitate visual analysis of exploration reports. For individual reports, it provides a summary of their content in graph form, a gallery of extracted figures and tables, and a list of similar reports based on shared geological keywords. In addition, it assists document search efforts through auto-generated keyword suggestions which are based on associations of keywords learnt by the system from all reports in the repository. While the text mining methods reported here is the foundation for further development to incorporate semantic analysis towards geological knowledge extraction, the outcomes of this study demonstrate the effectiveness of automated text analysis in supporting a fast analysis of a large number of reports to identify the targeted mineral systems and their associated geological environments.

In a recent article published in EPSL, Uzel et al. (2015) reported a paleomagnetic evidence on various rock types from Western Anatolia. It has been suggested that vertical axis rotations driven by the differential stretching along the Izmir Balikesir Transfer Zone (IBTZ) were caused by slab detachment and slab tear processes at the northern edge of subducting African slab. Although the paper supplies high quality data regarding the geological evolution of western Anatolia, some points need to clarified in light of recently published data.

Based on core and outcrop profile observation, the characteristics and reservoir significance in oil and gas accumulation of mud mounds in the Sinian Dengying Formation of the Sichuan Basin were studied. Small-scale mud mounds in platform are widespread in the Sinian Dengying Formation, Sichuan Basin, mostly less than 2 m thick per cycle, but high in occurrence frequency, especially in Member 2 and Member 4 of the Sinian Dengying Formation. Particles constituting the mud mounds are thrombolite, algal stromatolite, oncolite and bindstone, related to cyanobacteria biocoenosis buildup, which bind and capture lime mud for the mud mound construction, and the relevant rock types include algal bound clotted dolomitite, algal bound frame-dolomitite, and undulating-cylindrical algal stromatolite associated with clotted dolomitite. Multiphase mud mounds with positive relief have abundant frame structures, zebra structures and stromatactis. Two kinds of depositional models are mound base-core-flat and mound base-core-cap, the former is more common. The mud mounds are closely related to reservoirs. Different sizes of pores developed in the mud mound core provide space for oil and gas accumulation, so the mound-shoal complex is the main exploration target of the Sinian Dengying Formation. Key words: mud mound, cyanobacteria, algal binding clotted dolomitite, algal binding frame-dolomitite, framework structure, Sinian Dengying Formation, Sichuan Basin, dolomite reservoir

Determining the spatial relationships between various geological features and mineralisation is not only important for understanding the ore genesis of mineral deposits, but can also help to guide mineral exploration by providing predictive mineral maps. In this GIS-based study, we quantify the spatial relationships between gold mineralisation and plausible controlling factors in the central part of the St Ives area, Western Australia. We weigh plausible control factors including rock types, lithological boundaries and faults, using gold occurrences in drill-cores, and then apply the weights to the geological data to generate a predictive map for the entire St Ives area. The three major findings of this study are: (1) all major gold deposits are controlled by faults, and small-scale fault systems have a stronger correlation with gold mineralisation than large faults; (2) felsic to intermediate intrusive rocks show strong correlations with gold mineralisation, whereas metamorphic mafic rocks (greenstones) possibly acted as part of the broad regional environment for the mineral province rather than as a factor controlling the exact locations of the deposits; and (3) our predictive mapping indicates that the southeast part of the St Ives goldfield has a high potential for discovering new gold mineralisation.

[1] Each Mars Exploration Rover carries a Rock Abrasion Tool (RAT) whose intended use was to abrade the outer surfaces of rocks to expose more pristine material. Motor currents drawn by the RAT motors are related to the strength and hardness of rock surfaces undergoing abrasion, and these data can be used to infer more about a target rock's physical properties. However, no calibration of the RAT exists. Here, we attempt to derive an empirical correlation using an assemblage of terrestrial rocks and apply this correlation to data returned by the rover Spirit. The results demonstrate a positive correlation between rock strength and RAT grind energy for rocks with compressive strengths less than about 150 MPa, a category that includes all but the strongest intact rocks. Applying this correlation to rocks abraded by Spirit's RAT, the results indicate a large divide in strength between more competent basaltic rocks encountered in the plains of Gusev crater (Adirondack-class rocks) and the weaker variety of rock types measured in the Columbia Hills. Adirondack-class rocks have estimated compressive strengths in the range of 70–130 MPa and are significantly less strong than fresh terrestrial basalts; this may be indicative of a degree of weathering-induced weakening. Rock types in the Columbia Hills (Wishstone, Watchtower, Clovis, and Peace class) all have compressive strengths

Two geochemical reference materials of Himalayan origin named DG-H (a granite) and AM-H (an amphibolite) prepared by the Wadia Institute of Himalayan Geology Dehradun are described. Both samples were collected from the NW Himachal Himalaya in India. With the participation of analysts from more than forty international laboratories, element determination data collected during the past 10 years for characterisation of the samples was processed to assign working values using statistical procedures in use for this purpose. Earlier work published on these samples is incorporated in the present communication making it an updated document. The typical chemical and petrological characteristics of these two samples may prove useful for method validation and calibration of analytical instruments used for analysing similar rock types, and for widening the analytical range of several analytical methods used for geochemical analysis. Deux materiaux de reference geochimiques provenant de l'orogene Himalayen, nomme DG-H (un granite) et AM-H (une amphibolite) et prepare par l'Institut Wadia de geologie de l'Himalaya situe a Dehradun sont decrits. Les deux echantillons ont ete preleves dans le NO de l'Himalaya Himachal en Inde. Avec la participation d'analystes de plus de quarante laboratoires internationaux, les donnees d'elements chimiques recueillies au cours des dix dernieres annees, pour la caracterisation des echantillons ont ete traitees en utilisant les methodes statistiques en usage pour ce type d'etude afin d'affecter des valeurs de travail. Les travaux anterieurs publies sur ces echantillons sont incorpores dans la presente communication, ce qui en fait un document a jour. Les caracteristiques chimiques et petrographiques typiques de ces deux echantillons peuvent s'averer utile pour la validation des methodes et l'etalonnage des instruments analytiques utilises pour l'analyse de types de roches similaires, et pour elargir la gamme d'analyse de plusieurs methodes d'analyse geochimique.

A major challenge for mineral exploration geologists is the development of a transparent and reproducible approach to targeting exploration efforts, particularly at the regional to camp scales, in terranes under difficult cover where exploration and opportunity costs are high. In this study, a three-pronged approach is used for identifying the most prospective ground for orogenic gold deposits in the Paleoproterozoic Granite-Tanami Orogen (GTO) in Western Australia. A key input to the analyses is the recent development of a 4D model of the GTO architectural evolution that provides new insights on the spatio-temporal controls over orogenic gold occurrences in the area; in particular, on the role of pre-mineralization (pre-1795 Ma) D GTOE –D GTO1 –D GTO2 architecture in localization of gold deposits and the spatial distribution of rock types in 3D. This information is used to build up a model of orogenic gold minerals system in the area, which is then integrated into the three mutually independent but complementary mineral prospectivity maps namely, a concept-driven “manual” and “fuzzy” analysis; and a data-driven “automated” analysis. The manual analysis involved: (1) generation of a process-based gold mineral systems template to aid target selection; (2) manual delineation of targets; (3) manual estimation of the probability of occurrence of each critical mineralization process based on the available information; and (4) combining the above probabilities to derive the relative probability of occurrence of orogenic gold deposits in each of the targets. The knowledge-based Geological Information System (GIS) analysis attempts to replicate the expert knowledge used in the manual approach, but queried in a more systematic format to eliminate human heuristic bias. This involves representing the critical mineralization processes in the form of spatial predictor maps and systematically querying them through the use of a fuzzy logic model to integrate the predictor maps and to derive the western GTO orogenic gold prospectivity map. The data-driven ‘empirical’ GIS analysis uses no expert knowledge. Instead it employs statistical measures to evaluate the spatial associations between known deposits and predictor maps to establish weights for each predictor layer then combines these layers into a predictive map using a Weights of Evidence (WofE) approach. Application of a mineral systems approach in the manual analysis and the fuzzy analysis is critical: potential high value targets identified by these approaches in the western GTO lie largely under cover, whereas traditional manual targeting is biased to areas of outcrop or sub-crop amenable to direct detection technology such as exploration geochemistry, and therefore towards areas that are data rich. The results show the power of combining the three approaches to prioritize areas for exploration. While the manual analysis identifies and employs human intuition and can see through incomplete datasets, it is difficult to filter out human bias and to systematically apply to a large region. The fuzzy method is more systematic, and highlights areas that the manual analysis has undervalued, but lacks the intuitive power of the human mind that refines the target by seeing through incomplete datasets. The empirical WoE method highlights correlations with favorable host stratigraphy and highlights the control of an early set of structures potentially undervalued in the knowledge driven approaches, yet is biased due to the incomplete nature of exploration datasets and lack of abundant gold deposits due to the extensive cover. The results indicate that the most prospective areas for orogenic gold in western GTO are located in the central part of the study area, largely in areas blind to previous exploration efforts. According to our study, the procedure to follow should be to undertake the analyses in the following order: manual prospectivity analysis, followed by the conceptual fuzzy approach, followed by the empirical GIS-based method. Undertaking the manual analysis first is important to prevent explorationists from being biased by the automated GIS-based outputs. It is however emphasized that all of the prospectivity outputs from these three methods are possible, and they should not be treated as ‘treasure maps’, but instead, as decision-support aids. Therefore, a final manual prospectivity analysis redefined by the mutual consideration of output from all of the methods is required. The strategy employed in this study constitutes a new template for best-practice in terrane- to camp-scale exploration targeting that can be applied to different terranes and deposit types, particularly in terranes under cover, and provides a step forward in managing uncertainty in the exploration targeting process.

A self-organizing map (SOM) approach has been used to provide an integrated spatial analysis and classification of airborne geophysical data collected over the Brazilian Amazon. Magnetic and gamma ray spectrometric data were used to extract geophysical signatures related to the spatial distribution of rock types and to produce a geologic map over the prospective Anapu-Tuerê region. Particular emphasis was given to discriminating and identifying rock types, and the processes related to gold mineralization, which are known to occur in the Anapu-Tuerê region. SOM was able to identify and map distinctive geophysical signatures related to the various geologic units identified on the published geologic map. Furthermore, SOM was able to identify and enhance very subtle signatures derived jointly from the magnetic and gamma ray spectrometric data that could be related to geologic processes present in the area. These results demonstrate the effectiveness of using SOM as a tool for geophysical data analysis and for semiautomated mapping in regions such as the Amazon.

Geodetic studies have shown that deformation rates around several major strike‐slip faults are asymmetric. This asymmetry is often explained in terms of a crustal‐scale contrast in elastic properties across the fault. Motivated by the fact that elasticity variations for different rock types under similar ambient conditions are generally modest, whereas effective viscosity may vary over orders of magnitude, we have developed earthquake‐cycle models to evaluate whether contrasts in viscosity structure and effective plate thickness can explain observed asymmetric surface deformation. We find that an increased plate‐thickness contrast results in a more asymmetric surface‐velocity profile. Furthermore, for the same plate‐thickness contrast, asymmetry of the surface deformation is most pronounced in models with a low‐viscosity substrate. Initially, velocities relative to a point on the fault are higher on the side with the thin plate; however, late in the interseismic interval this reverses, and these velocities are higher on the side with the thick plate. Models with a contrast in the substrate viscosity on either side of the fault and a uniform plate thickness show behavior similar to that of the variable‐thickness plate models. In both suites of asymmetric models, the surface velocity at the fault varies through the earthquake cycle. This is necessary to reconcile symmetric coseismic deformation, asymmetric interseismic deformation, and the requirement of zero strain in the blocks on either side of the fault over an earthquake cycle. Given the modest asymmetry in surface deformation for models capable of producing localized interseismic deformation around the fault (i.e., models with high substrate viscosities), we conclude that lateral contrasts in viscosity or effective plate thickness cannot produce dramatic asymmetries in Global Positioning System surface‐velocity profiles across major strike‐slip faults.

Review article: Geochemical analysis is an essential tool for the confirmation and study of impact structures and the characterization of the various rock types involved (target rocks, impact breccias, melt rocks, etc.). Concentrations and interelement ratios of the platinum-group elements, as well as the osmium and chromium isotope systems, allow quantification of extraterrestrial components and the identification of impactor types in impact deposits.In addition, chemolithostratigraphy can reveal the possible role of impacts in environmental change throughout the geologic record. This article deals predominantly with terrestrial impact structures.

Basic regularities of secondary processes in reservoir rocks of the Yarakta Horizon are described with rocks in the Yarakta field as example. To achieve the formulated goal, we elucidated rock types in the studied section, its structure and distribution of reservoir rocks, as well as types of secondary alterations and their influence on filtration-capacity properties. The studies revealed that reservoir rocks of the Yarakta Horizon were formed on an alluvial-deltaic plain on the southeastern slope of the Nepa-Botuoba anteclise. The pore space of reservoir rocks is determined by conditions of their formation and peculiarities of secondary alterations. Maximal filtration-capacity values are characteristic of gritstones, as well as coarse-grained and inequigranular sandstones developed in the lower and middle parts of the Yarakta Horizon. The intergranular space of reservoir rocks in the lower part of the reservoir is substantially “healed” by secondary processes (regeneration, dolomitization, sulfatization, and salinization), probably, due to the gravitational seepage of stratal fluids, mineralization of which increased with time.

Multiple sets of compaction bands of southwestern Utah occur in Navajo Sandstone near a bend in the adjacent East Kaibab monocline. Forward mechanical models of blind-thrust fault deformation are used in this paper to investigate the spatial relationship between compaction bands and fault-related folding. Results are consistent with the East Kaibab monocline being underlain by a west-dipping blind high-angle reverse fault between ~ 1.5 and 5 km depth below the top of the Navajo Sandstone. Reverse slip along this reactivated fault during the Laramide orogeny is inferred to have produced values of compactional normal strain that were largest in the footwall near the concave map-view bend in the monocline. The calculated compactional normal strains and Coulomb stress increases are consistent with the field occurrence of pure and shear-enhanced compaction bands in this area. Bends, relays, stepovers, or other geometric complexities above blind reverse faults are thus inferred to be potential sites for compaction band localization in appropriate rock types.

The tight sandstones of the Upper Triassic Xujiahe Formation (T3x) constitute important gas reservoirs in western Sichuan. The Xujiahe sandstones are characterized by low to very low porosity (av. 5.22% and 3.62% for the T3x4 and T3x2 sandstones, respectively), extremely low permeability (av. 0.060 mD and 0.058 mD for the T3x4 and T3x2 sandstones, respectively), strong heterogeneity, micronano pore throat, and poor pore throat sorting. As a result of complex pore structure and the occurrence of fractures, weak correlations exist between petrophysical properties and pore throat size, demonstrating that porosity or pore throat size alone does not serve as a good permeability predictor. Much improved correlations can be obtained between permeability and porosity when pore throat radii are incorporated. Correlations between porosity, permeability, and pore throat radii corresponding to different saturations of mercury were established, showing that the pore throat radius at 20% mercury saturation (R20) is the best permeability predictor. Multivariate regression analysis and artificial neural network (ANN) methods were used to establish permeability prediction models and the unique characteristics of neural networks enable them to be more successful in predicting permeability than the multivariate regression model. In addition, four petrophysical rock types can be identified based on the distributions of R20, each exhibiting distinct petrophysical properties and corresponding to different flow units.

The influence of rock strength properties on Jaw Crusher performance was carried out to determine the effect of rock strength on crushing time and grain size distribution of the rocks. Investigation was conducted on four different rock samples namely marble, dolomite, limestone and granite which were representatively selected from fragmented lumps in quarries. Unconfined compressive strength and Point load tests were carried out on each rock sample as well as crushing time and size analysis. The results of the strength parameters of each sample were correlated with the crushing time and the grain size distribution of the rock types. The results of the strength tests show that granite has the highest mean value of 101.67 MPa for Unconfined Compressive Strength (UCS) test, 6.43 MPa for Point Load test while dolomite has the least mean value of 30.56 MPa for UCS test and 0.95 MPa for Point Load test. According to the International Society for Rock Mechanic (ISRM) standard, the granite rock sample may be classified as having very high strength and dolomite rock sample, low strength. Also, the granite rock has the highest crushing time (21.0 s) and dolomite rock has the least value (5.0 s). Based on the results of the investigation, it was found out that there is a great influence of strength properties on crushing time of rock types.

Geochemical anomaly separation using the concentration-area (C-A) method at Kahang (Gor Gor) porphyry system in Central Iran is studied in this work. Lithogeochemical data sets were used in this geochemical survey which was conducted for the exploration for Cu mineralization in dioritic and andesitic units at Kahang Cu-Mo porphyry system. Similar surveys were also carried out for Mo and Au exploration in these rock units. The obtained results have been interpreted using rather extensive set of information available for each mineralized area, consists of detailed geological mapping, structural interpretation and alteration data. Anomalous threshold values for the mineralized zone were computed and compared with the statistical methods based on the data obtained from chemical analysis of samples for the lithological units. Several anomalies at a local scale were identified for Cu (224 ppm), Mo (63 ppm), and Au (31 ppb), and the obtained results suggests existence of local Cu anomalies whose magnitude generally is above 1000 ppm. The correlation between these threshold values and ore grades is clearly interpreted in this investigation. Also, the log-log plots show existence of three stages of Cu enrichment, and two enrichment stages for Mo and Au. The third and most important mineralization event is responsible for the presence of Cu at grades above 1995 ppm. The identified anomalies in Kahang porphyry system, and distribution of the rock types, are mainly monzodiorite and andesitic units, do have special correlation with Cu and monzonitic and dioritic rocks, especially monzodioritic type, which is of considerable emphasis. The threshold values obtained for each element are always lower than their mean content in the rocks. The study shows threshold values for Cu is clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of phyllic, argillic and propyllitic alterations within the monzonitic and dioritic rocks especially in monzodioritic type. The obtained results were compared with fault distribution patterns which reveal a positive direct correlation between mineralization in anomalous areas and the faults present in the mineralized system. © 2009 Elsevier B.V.

Feldspars are among the most common minerals in the Earth’s crust, and are found in a variety of rock types. Diffusion in feldspars has been studied for well over half a century, with Rosenqvist’s (1949) measurements of Ra and Pb diffusion among the earliest published works. Major efforts in measuring diffusion in feldspars, primarily of the alkali elements, were undertaken in the early 1970s, with the work of Bailey (1971), Lin and Yund (1972), Petrovic (1972), Foland (1974), Giletti et al. (1974) and Kasper (1975). Many of these early studies used bulk-exchange techniques rather than direct depth profiling, or employed methods of limited depth resolution such as serial sectioning; these methods, while state of the art for their time, impose several limitations, including a range of measurement restricted to relatively fast diffusivities, and the difficulty of distinguishing the effects on measured chemical or isotopic compositions that may be a result of diffusional fast paths, surface reaction, and/or other artifacts, from those contributions due solely to volume diffusion. Development of high-resolution depth profiling techniques, such as SIMS and RBS, have permitted measurement of much smaller diffusivities for a broader range of elements, and reduced some of the uncertainties characteristic of bulk-exchange methods. Feldspar diffusion data have been previously summarized in Yund (1983) and Smith and Brown (1988), and were included in Brady’s (1995) compilation of diffusion data for silicate minerals. Since the publication of these works, there have been numerous diffusion studies of feldspars encompassing a range of compositions in alkali feldspars and across the plagioclase series. These have included measurements of diffusion of major elements Na, K, Ca, Ba, oxygen and silicon, as well as Na-K and CaAl-NaSi interdiffusion, diffusion of noble gases, and diffusion of minor and trace elements including Fe, Mg, Sr, …