The Cougar Gulch area near Coeur d’Alene, Idaho, is a newly recognized Paleoproterozoic to Archean basement occurrence located in the southern Priest River complex. Here, a structural culmination exposes deeper levels of the core complex infrastructure, similar to where Archean basement is exposed in the northern portion of the complex near Priest River, Idaho. At Cougar Gulch, the basement rocks are composed of a variety of granitic orthogneisses and amphibolite, which are unconformably overlain by a graphite-bearing orthoquartzite. The orthoquartzite is in turn overlain by the Hauser Lake Gneiss. The similarity of structure, metamorphic fabrics, and kinematics here and in the northern portions of the complex is consistent with the Cougar Gulch area being the southern continuation of the Spokane dome mylonite zone.Neoarchean amphibolites (2.65 Ga) have been identified as part of the basement sequence. These amphibolites had a basaltic protolith and can be distinguished geochemically from amphibolites found within the overlying Hauser Lake Gneiss (Mesoproterozoic, Lower Belt Group equivalent), which are metamorphosed Moyie sills. The Archean amphibolites have steeper REE (rare earth element) slopes and consistently higher REE values. Protoliths of the Paleoproterozoic orthogneisses (1.87–1.86 Ga) are calc-alkaline, “I-type” monzogranites and granodiorites, which exhibit subduction-related geochemical characteristics such as high LILE:HFSE (large ion lithophile element: high field strength element) concentrations, along with characteristic depletions in Nb, Ta, P, Ti, and Eu. A second distinctive geochemical unit of orthogneiss, the Kidd Creek tonalite, exhibits TTG (tonalite-trondhjemite-granodiorite) geochemical characteristics. The Kidd Creek tonalite has Sr/Y and La/Yb ratios, along with Y and HREE (heavy rare earth element) concentrations (no Eu anomalies) similar to Precambrian TTG compositions formed in subduction settings. Detrital zircon data from the orthoquartzite unit, along with characteristic graphite and its consistent stratigraphic level support correlation to the pre-Belt Gold Cup Quartzite in the northern part of the complex.

The knowledge that societies have of their geological environment and of the materials used in their heritage is of great importance for the sustainable use and conservation of traditional natural stone architecture. Similar weathering mechanisms occur in natural environments and the built environment and, in both cases, weathering may endanger both natural and built heritage. The Sierra de Guadarrama (Spanish Central System) is a privileged area in which natural and built heritage coexist. This paper describes an area of particular monumental and geological interest on the northern slopes of the Sierra de Guadarrama; its main aim is to propose an itinerary for members of the public, presented as a route through the area around Segovia, in which architecture/cultural heritage and an Earth sciences approach are brought together with an educational purpose. To this end, some connections are established between weathering forms in natural and built environments, as well as between the lithological characteristics of the rocks used in construction of ancient monuments in the area and the distribution of stresses and loads of walls.

The shock metamorphism of rocks and minerals is an important consequence of hypervelocity impact events. Much remains to be understood regarding effects in accessory geochronology minerals, such as the effect of very high shock conditions on zircon (ZrSiO4). This study explores the effects of shock metamorphism on zircon in crystalline, quartzofeldspathic basement rocks from the ~23–39-m.y.-old, 23-km-diameter Haughton impact structure on Devon Island, Arctic Canada. This is a valuable location for this study because the structure is very well preserved and contains materials covering a wide range of shock levels. A petrographic survey of 255 zircon grains revealed a variety of microfeatures, including fracturing, planar features, and granular texture, as well as a microporosity texture in highly shocked (level 6, 55–60 GPa) zircon grains. This survey showed that general trends exist in the proportions of grains from each shock level that display certain microscopic features, including a decrease in fractures and appearance of granular textures related to increasing shock pressures. Raman spectroscopy data from 22 zircon grains showed evidence of radiation damage, impurities, the presence of reidite, and recrystallized grains. The overall pattern with increasing shock level is that of metamict, low-crystallinity zircon in basement gneiss outside the impact structure, increased crystallinity and preservation of reidite in an intermediate-shock-level sample, and highly crystalline, annealed zircon (no reidite) in highly shocked samples otherwise composed entirely of glass. The sequence of structural and phase changes observed in this study is consistent with the findings of previous work, and our results expand the body of knowledge about the series of shock features that can be applied to other similar structures, both on Earth and other planetary bodies.

The Mesoarchean Kola-Karelia continent in the eastern Fennoscandian Shield includes three tectonic provinces, Kola, Karelia and Belomoria, that were formed by the Paleoarchean and Mesoarchean microcontinents. Traces of Mesoarchean tonalite-trondhjemite-granodiorite (TTG)-type early crust were documented in all of the most ancient units of the Kola-Karelia continent. Ancient crust was revealed and dated in the Ranua and Iisalmi microcontinents, 3.5–3.4 Ga; Vodlozero and Khetolambina microcontinents, 3.25–3.15 Ga; Kuhmo-Segozero microcontinent, ~3.0 Ga; Murmansk and Inari-Kola microcontinents, 2.93 Ga; and Kianta microcontinent, 2.83–2.81 Ga. In the older (>3.0 Ga) tectonic units and microcontinents, the ancient crust was possibly formed in brief bursts of endogenic activity. In younger microcontinents (3.0–2.93 Ga), these processes could continue until 2.8 and even 2.72 Ga. The tectonic settings in which early TTG crust has been produced are largely uncertain. The primary melt glassy inclusions with a glass phase in cores of prismatic zircon crystals from TTG gneisses provide evidence for the volcanic origin of gneiss protolith. Suggested genetic modeling of TTG-type complexes assumes that felsic K-Na melts with positive Eu anomaly are a product of dry high-temperature partial melting of the previously formed mafic-to-felsic crustal rocks and/or thick older TTG crust. Positive Eu anomaly in the eutectic is directly related to the predominance of plagioclase and K-feldspar in the melt. TTG-type crust melted to produce granite-granodiorite (GG) rocks. Earliest microcontinents are separated by Mesoarchean greenstone belts (mainly 3.05–2.85 Ga, in some cases up to 2.75 Ga), which are fragments of paleo–island-arc systems accreted to their margins: the Kolmozero-Voronya, Central Belomorian, Vedlozero-Segozero, Sumozero-Kenozero, and Tipasjärvi-Kuhmo-Suomussalmi belts; and the mature island arcs (microcontinents): Khetolambina and Kovdozero. These structural units are characterized by significant extent, close to rectilinear trend, localization along the boundaries between Archean microcontinents, and a specific set of petrotectonic assemblages (basalt-andesite-rhyolite, komatiite-tholeiite, and andesite-dacite associations). The recently discovered Meso-Neoarchean Belomorian eclogite province that is structurally linked with the Central Belomorian greenstone belt contains two eclogite associations distributed within TTG gneisses: the subduction-type Salma association and the Gridino eclogitized mafic dikes. The protolith of the Salma eclogites is thought to have been a sequence of gabbro, Fe-Ti gabbro, and troctolite, formed at ca. 2.9 Ga in a slow-spreading ridge (similar to the Southwest Indian Ridge). The main subduction and eclogite-facies events occurred between ca. 2.87 and ca. 2.82 Ga. Mafic magma injections into the crust of the active margin that led to formation of the Grigino dike swarm were associated with emplacement of a mid-ocean ridge in a subduction zone, beginning at ca. 2.87 Ga. Crustal delamination of the active margin and subsequent involvement of the lower crust in subduction 2.87–2.82 Ga ago led to high-pressure metamorphism of the Gridino dikes that reached eclogite-facies conditions during a collision event between 2.82 and 2.78 Ga. This collision resulted in consolidation of the Karelia, Kola, and Khetolamba blocks and formation of the Mesoarchean Belomorian accretionary-collisional orogen. To date, the subduction-related Salma eclogites provide the most complete and meaningful information on the nature of plate tectonics in the Archean, from ocean-floor spreading to subduction and collision. The Kovdozero granite-greenstone terrain that separates the Khetolambina and Kuhmo-Segozero microcontinents is formed by TTG granitoids and gneisses hosting metasediments and metavolcanics of several greenstone belts, which belonged to the Parandovo-Tiksheozero island arc that existed from ca. 2.81 to 2.77 Ga. The Iringora greenstone belt includes the ophiolite complex of the same name with an age of 2.78 Ga. The collision of microcontinents resulted in the upward squeezing of the island arc and the obduction of its marginal portions onto surrounding structures.

Beginning ca. 2.76 Ga, evolution of the Kola-Karelia crust was related to the intracontinental high-temperature metamorphic (up to granulite facies) and magmatic events in combination with formation of the basins related to rifting and infilling with intracontinental volcanic and sedimentary sequences initiated by plume-type processes in the mantle. The geological events corresponding to intracontinental evolution were expressed not only in the formation of new rock associations, juvenile to a significant extent, but also in reworking of previously formed rocks. The age, content, and mode of geological activity are somewhat different in the Kola and the Karelian-Belomorian regions. The Karelian-Belomorian region is oval in plan view. The long axis of this oval extends for 600–700 km in the meridional direction; its maximum width is 400–450 km. The southern part of this oval structure is cut off along the NW-trending boundary with the Paleoproterozoic Svecofennian accretionary orogen. The main constituents of the Karelian-Belomorian region are: epicontinental sequences of greenstone belts (Kostomuksha, Khedozero-Bolsheozero, Gimoly-Sukkozero, Jalonvaara) and paragneiss belts (Hattu, Nurmes); granulite-gneiss complexes and intrusive enderbite-charnockite series; sanukitoid-type granitoid intrusions and lamprophyre dikes, along with migmatization and emplacement of within-plate young granites; and local manifestations of granulite-facies metamorphism superposed on older rocks. Concentric spatial distribution of related geological units is characteristic of the Karelian-Belomorian region. The geometric pattern of the region can be satisfactorily explained assuming initial activity of a mantle plume ca. 2.76 Ga in the central part of the region. A peak of activity was related to the events that occurred ca. 2.74–2.70 Ga. The geochronological data show that a region of high-temperature processes expanded from its center (2.76–2.73 Ga) to the periphery (2.74–2.70 Ga). The concentric character of the tectonic structure was eventually formed as a result of these processes. Widespread high-temperature magmatism and metamorphism in combination with formation of synformal and linear sedimentary basins indicate the setting of anorogenic extension and vigorous influx of extracrustal heat, i.e., a large event related to a mantle plume. In contrast to the Karelian-Belomorian hot region, the coeval Kola region of intracontinental manifestations of high-temperature metamorphism and magmatism is characterized by oval-block geometry. This area, confined to the central part of the Kola Peninsula, extends for 600 km in the northwestern direction, having a width of ~200 km. It is possible that this area extends further to the southeast beneath the platform cover. The main tectonic units are the intracontinental greenstone belts (Sør-Varanger, Titovka, Uraguba, Olenegorsk, Voche-Lambina, Kachalovka, Runijoki–Khikhnajarvi, and Strelna system) in the Inari-Kola microcontinent, the granulite-gneiss Central Kola complex, and the Keivy volcanotectonic paleodepression. Sanukitoid intrusions play a modest role. The Keivy volcanotectonic paleodepression is situated in the eastern Kola Peninsula. Rocks of this tectonic unit are peculiar, and many of them have no obvious analogs in the Fennoscandian Shield or elsewhere. The major Neoarchean amphibolite-gneiss association consists of calc-alkaline to subalkaline garnet-biotite and subalkaline-peralkaline aegirine-arfvedsonite gneisses, as well as biotite-amphibole and amphibole gneisses, amphibolites, and rheomorphic alkali granites. In the western part of the paleodepression, gneisses (metavolcanic rocks) are cut through by small Sakharjok and Kuljok nepheline syenite intrusions. Geochronological estimates characterize two outbursts of magmatic activity separated by a long gap. The early outburst corresponds to magmatic crystallization of calc-alkaline metavolcanic rocks at 2.90–2.87 Ga. The second vigorous outburst documented at 2.68–2.63 Ga corresponds to eruption of subalkaline and subalkaline-peralkaline volcanic rocks, emplacement of alkali and nepheline syenites, and crystallization of gabbro-anorthosite of the Tsaga-Acherjok complex. The duration of the main magmatic phase is ~50 m.y., whereas the preceding gap lasted for ~200 m.y. A model of a volcanotectonic depression largely filled with pyroclastic flows seems plausible to explain pre-metamorphic events. Such manifestations of volcanic activity are inherent to intracontinental domains and related to activity of mantle plumes; similar processes can also develop in the back extensional zone of active continental margins. The synchronism of felsic volcanism and emplacement of the typically intracontinental gabbro-anorthosites form a sound argument in favor of an intracontinental setting for the Keivy paleodepression. The geometry of the Kola region can be satisfactorily explained in terms of mantle-plume activity noted ca. 2.76 Ga in the marginal part of this region; a peak of activity in its central part is related to the events that happened ca. 2.68–2.63 Ga.

The basement of the East European Platform corresponding to northeastern Sarmatia is known as the Voronezh Crystalline Massif (VCM). The Kursk microcontinent, which lies in northeastern Sarmatia, occupies the bulk of the Voronezh Crystalline Massif. The predominant portion of the Kursk microcontinent is a combination of sedimentary–volcanic complexes making up greenstone belts and granite-gneiss (granite-migmatite) associations of the granite-greenstone domain bearing the same name. The smaller Kursk–Besedino granulite-gneiss terrane is situated in the central part of the microcontinent. The following sequence of events may be proposed as a preliminary model of crustal evolution: (1) Paleo- to Mesoarchean: formation of granite-greenstone continental crust (3.7–3.1 Ga); (2) events related to the activity of a mantle plume 2.85–2.82 Ga ago: underplating by mantle-derived magmas; formation of an intracontinental depression; its rapid filling with sediments, including Fe-rich varieties; and metamorphism of granite-greenstone basement and the sedimentary fill of the depression; and (3) Neoarchean and/or Paleoproterozoic: collisional compression and transformation of the depression into a synformal tectonic nappe.

The major tectonic units of the Neoarchean Volgo-Uralia continent, which is ~600,000 km2 in area, are contrastingly expressed in regional gravity and magnetic maps. Interpretations of seismic images of the crust along the TATSEIS geotraverse in combination with 3D density and magnetic crust models provide insights into the volumetric representation of tectonic structures of various ranks. Granulite-gneiss crust of Volgo-Uralia is characterized by elevated thickness (~60 km and locally up to 65–70 km). The deep structure of Volgo-Uralia assumes that the entire crustal section, including the lower crust, is composed of high-density granulite metamorphic facies rocks. Specific structural units called ovoids play the main role in the structure of this continent. The ovoids are bowl-shaped crustal blocks, round or oval in plan view, 300–600 km across, and with the base reaching a level of crust-mantle interface at ~60 km. Ovoids are bounded by conic surfaces of reverse (thrust)-faults, along which their outer parts are thrust over the framework. The Tokmov, Buzuluk, Verkhnekamsk, Krasnoufimsk, and Orenburg ovoids, which generally are not in contact with one another, are dominated by mafic granulites, gabbroic rocks, gabbroanorthosites, and ultramafic rocks. A significant contribution of deep-seated intrusive rocks suggests that metamorphism developed in the lower and middle crust at high PT parameters that exceed the maximum estimates (940–950 °C, 9.5 kbar) recorded in samples of borehole cores. The interovoidal space is occupied by elongated oval synforms up to 200–400 km long. This space is considered to be an interovoidal domain, which includes three relatively narrow, compressed synforms (Yelabuga-Bondyug, Kilmez, Chusovaya) and four oval synforms (Srednevyatka, Verkhnevyatka, North-Tatar, Almetevsk). The Tokmov ovoid is framed in the southeast by the Tuma and Penza belts. Synforms are filled with metasedimentary granulites and mafic metaigneous rocks. The protoliths were formed over the time interval from 3.4–3.2 to 3.1–3.0 Ga. The internal zoning of the Volgo-Uralia crust is related to numerous local centers within ovoids and interovoidal region. At least two high-temperature metamorphic events were followed by periods of retrogression: 2.74–2.70 and 2.62–2.59 Ga. The areal and especially high-temperature character of tectonothermal processes during formation of the Neoarchean crust of the Volgo-Uralia Craton, and distinct geometrization of space with recognition of several concentric domains, finds a universal explanation in ascent of multiple plumes.

In this chapter, the available seismic and geological data are integrated and applied to the East European craton as a whole. The deep structure and seismic characteristics of the granite-greenstone crust in the Archean microcontinents vary significantly. The unevenly distributed and vaguely oriented short reflections are occasionally gathered into packets. The intensely reflecting bodies with high acoustic impedance correspond to greenstone belts reaching many tens of kilometers in extent. The oval acoustically transparent domains in the middle-crustal level are composed of moderately dense rocks that correspond to granitoid plutons. The total thickness of the crust in granite-greenstone domains can vary from 40 km in the Kola-Karelia continent to 50 km in the Kursk microcontinent. The Archean granulite-gneiss complexes form the delineated belts localized in the upper crust. These are synformal tectonic nappes, the vertical thickness of which reaches 15 km. A special case is the Volgo-Uralia continent, the crust of which is completely composed of granulite-gneiss rocks partly replaced by retrograde metamorphic assemblages. The granulite-gneiss crust is distinguished by significant thickness (~60 km; maximum 65–70 km). The lower-crustal “layer,” ~35 km thick, consists of inclined tectonic sheets plunging in a northwestern direction and penetrating the upper mantle. The interface between upper and lower crust is replaced by acoustically transparent granitoid crust 10–20 km in thickness. The Middle Paleoproterozoic East Voronezh intracontinental collisional orogen between the Archean Kursk and the Khopior microcontinents is represented by a “crocodile-jaw” structure. The structural pattern in the seismic image of the crust clearly indicates a Paleoproterozoic age of lower-crustal layer and shows the absence of the Paleoproterozoic lower-crustal complex at the base of the Kursk craton proper. The Late Paleoproterozoic intracontinental Lapland–Mid-Russia–South Baltia orogen surrounds in a wide arc the Karelian craton in the northeast, east, south, and southwest. The upper crust in the inner zone of the orogen in the Mid-Russia sector is composed of alternating granulite-gneiss and gneiss-migmatite-amphibolite tectonic sheets 5–10 km thick, deformed in gentle synformal folds. The marginal zones consist of south-plunging tectonic sheets of the Totma belt in the north and the Aprelevka belt in the south. The Totma sheet, reaching 10 km in thickness and dipping at a mean angle of 5°–10°, is traced by reflectors from the basement surface (interval 1700–1800 km) to the crust-mantle interface (interval 2000–2200 km). These parameters, along with composition of the rocks, allow interpretation of the Totma belt as a suture zone, separating the synformal structural assemblage from the lower crust. In the Paleoproterozoic Svecofennian accretionary orogen, interpretation of the FIRE-1 profile shows that the Central Finland granitoid massif is a nearly horizontal, sheetlike intrusive body that conceals an accretionary complex—a succession of tectonic sheets, 10–20 km thick, which plunges northeast at angles of 10°–12° down to the crust-mantle interface at a depth of 65 km and can be traced beneath the margin of the Karelian craton for more than 150 km. The lower-crustal layer, often called a reflectivity zone, is always present at the base of the Lapland–Mid-Russia–South Baltia orogen and the Archean cratons surrounded by this arcuate orogen. This layer was formed in the Early Paleoproterozoic as a result of under- and interplating of mantle melts accompanied by granulite-facies metamorphism. The increase in thickness of the lower-crustal layer is related to hummocking (mutual over- and underthrusting and wedging) of tectonic sheets at the base of the crust. The lower-crustal layer of the Kola-Karelia continent was formed before the main collisional events, which took place in the Late Paleoproterozoic. The structure of the crust depicted by seismic reflectors indicates in some cases that the crust-mantle interface has remained unchanged since the time of crust formation, whereas in other situations, this boundary is younger than the bulk crust. The crust-mantle interface beneath the East European craton reveals manifold deviations from its persistent near-horizontal outline due to bending, plunging, and apparent dissolution of lower-crustal sheets in the mantle. The underlying upper mantle reveals a number of indistinct reflectors imaged as dashed lines, which trace lower-crustal structural elements incorporated into the mantle. These domains are regarded as crust-mantle mixtures. The crust images along the seismic lines exhibit widely varying structural features and degrees of contrast (sharpness) of the crust-mantle interface. The following structural and morphological types of the crust-mantle interface are distinguished beneath the East European craton: (1) a smooth, generally flat or horizontal or slightly sloping boundary with an abrupt decrease in number of reflectors at the lower edge of intensely reflecting layered lower crust; (2) a boundary similar to the previous type but periodically interrupted at sites where the sheetlike fragments of the lower crust sharply bend and sink into the mantle and acoustically as if they dissolve therein; (3) a serrated boundary in the regions of consecutive plunging lower-crustal tectonic sheets into the mantle; these domains are commonly conjugated: reverse-thrust assemblages in the upper crust rise in the same direction as the lower-crustal sheets plunge; (4) a serrated boundary confining from below the ensemble of inclined tectonic sheets that form the crust completely or partly; (5) a diffuse crust-mantle interface that is observed where a distinct lower-crustal reflectivity zone is absent; and (6) a phantom (disappearing) crust-mantle interface that separates acoustically transparent crustal and mantle domains that can be detected by seismic-refraction exploration. Integration of the entire body of information allowed us to simulate the 3D deep structure of the Early Precambrian crust of the East European craton as a whole using sections along the 1-EU geotraverse, cross-traverse 4B, TATSEIS regional profile, and FIRE-1 and FIRE-4 profiles. The 3D deep structure of the East European craton is represented by the tectonically delaminated Early Precambrian crust with a predominance of gently dipping boundaries between the main tectonic subdivisions and a complexly built crust-mantle interface. The integral model includes Archean granite-greenstone domains and granulite-gneiss areas and Paleoproterozoic accretionary and intracontinental collisional orogens.

The Older Metamorphic Group and the Older Metamorphic Tonalite Gneiss are classic examples of Palaeaoarchaean high-grade metamorphic rocks of the Singhbhum Craton of India. The Older Metamorphic Group is a supracrustal assemblage that was probably deposited as a greenstone belt-type succession before c. 3.32 Ga, the low-grade equivalents of which are found in parts of the Iron Ore Group. The Older Metamorphic Tonalite Gneiss represents a suite of granitoids that are tectonically interleaved with the supracrustal gneisses and that formed over an extended period of time, 3.53–3.45 Ga and possibly later, by processes of Archaean crustal growth.

At 100 Ma, about midway through the history of the emplacement of the northern part of Peninsular Ranges batholith, a regional-scale deformation zone1 developed that juxtaposed two major prebatholithic units. Deformation occurred as subduction transitioned from beneath oceanic crust to beneath continental crust. The deformation zone is well exposed at Searl Ridge, where the intensity of deformation attendant to the juxtaposition of the two prebatholithic units progressively increased from west to east over a distance of 5.5 km. In this 5.5-km-wide zone, a series of three progressive structural transpositions is recorded in the metasedimentary rocks. Many outcrops have two intersecting planar fabrics and a linear fabric produced by the intersecting planar fabrics. West to east within the deformation zone, the rock fabric changes from phyllitic to schistose, and the grade of metamorphism increases from greenschist to lower granulite. Plutonic rocks predating the deformation zone at the west edge of Searl Ridge were likewise deformed locally into rocks having a pronounced gneissic fabric. The transposition displacement produced a 300 °C gradient over a 4-km-wide zone of low-pressure, high-temperature, Buchan-type metamorphic mineral assemblages. The 300 °C gradient is based on biotite forming at a temperature of ~425 °C, and K-feldspar at ~750 °C. A 3–4 kbar pressure gradient across the deformation zone is inferred from a crystallization pressure of 2 kbar for the 120 Ma Domenigoni Valley pluton, located at the western edge of the deformation zone, and a 5–6.3 kbar pressure for the 100 Ma Lakeview Mountains pluton, emplaced in the eastern part, the latter being coeval with the formation of the deformation zone. If temperature increase is attributable entirely to difference in depth, and assuming an idealized 0.3 kbar increase in pressure per 1 km increase in crustal depth, the vertical displacement component of deformation within the deformation zone was 10–13 km.