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Drought is becoming more frequent and severe in numerous wine‐growing regions. Nevertheless, limited research has examined the legacy of recurrent droughts, focusing on leaf physiology and anatomy over consecutive seasons. We investigated drought legacies (after 2 years of drought exposure) in potted grapevines, focusing on stomatal behaviour under well‐watered conditions during the third year. Vines were subjected for two consecutive years to short‐ (SD) or long‐term (LD) seasonal droughts, or well‐watered conditions (WW). In the third year, all plants were grown without water limitation. Water potential and gas exchange were monitored throughout the three seasons, while leaf morpho‐anatomical traits were measured at the end of the third year. During droughts (1st and 2nd year), stem water potential of SD and LD plants fell below −1.1 MPa, with a consequent 75% reduction in stomatal conductance (gs) compared to WW. In the 3rd year, when all vines were daily irrigated to soil capacity (midday stem water potential ~ −0.3 MPa), 45% lower values of gs were observed in the ex‐LD group compared to both ex‐SD and ex‐WW. Reduced midrib vessel diameter, lower leaf theoretical hydraulic conductivity, and smaller stomata were measured in ex‐LD leaves compared to ex‐SD and ex‐WW, likely contributing to the reduced gas exchange. Our findings suggest that grapevines exposed to drought may adopt a more water‐conserving strategy in subsequent seasons, irrespective of current soil water availability, with the degree of change influenced by the intensity and duration of past drought events. [ABSTRACT FROM AUTHOR]

A system of precise pulse synchronization between a single-shot large-scale laser exploiting an acousto-optical modulator and a femtosecond high repetition rate laser is reported in this article. This opto-electronical system has been developed for synchronization of the sub-nanosecond kJ-class iodine photodissociation laser system (Prague Asterix Laser System--PALS) with the femtosecond 25-TW Ti:sapphire (Ti:Sa) laser operating at a repetition rate 1 kHz or 10 Hz depending on the required energy level of output pulses. At 1 kHz synchronization regime, a single femtosecond pulse of duration about 45 fs and a small energy less than 1 mJ are exploited as a probe beam for irradiation of a threeframe interferometer, while at 10 Hz repetition rate a single femtosecond pulse with higher energy about 7-10 mJ is exploited as a probe beam for irradiation of a two-channel polaro-interferometer. The synchronization accuracy ±100 ps between the PALS and the Ti:Sa laser pulses has been achieved in both regimes of synchronization. The femtosecond interferograms of laser-produced plasmas obtained by the three-frame interferometer and the femtosecond polarimetric images obtained by the two-frame polaro-interferometer confirm the full usefulness and correct functionality of the proposed method of synchronization. [ABSTRACT FROM AUTHOR]

The 221 Ma Bayan-Ulan (BU) granitic pluton occurs in the North Gobi rift of central Mongolia which was superimposed on the Paleozoic Central Asian Orogenic Belt (CAOB), an area characterized by voluminous juvenile crust. This large (>1000 km 2 ) pluton is part of an Early Mesozoic granitoid province in the central part of the CAOB. It consists mainly of alkali feldspar granites containing mesoperthite with interstitial quartz, minor Ca–Na and Na amphiboles and rare Fe-rich biotite. Graphic texture is common. The BU granites are fractionated, leucocratic, alkaline, A-type rocks that are enriched in incompatible elements, particularly Rb and Th and depleted in Ba, Sr, Eu and Ti. Most have ɛ Nd(T) values of +1.4 to +1.7 and T DM model ages ∼800 and 1200 Ma, and lie within the range of other A-type granites of the CAOB granitoid province. The granites are interpreted to have formed by the partial melting of underplated, Neoproterozoic, mildly-alkaline basalts in the lower crust, followed by fractional crystallization dominated by feldspars. The formation of the BU pluton and the coeval Khentei batholith, the largest Late Triassic intrusion in north-central Mongolia, appears to be related either to a plume or to the closure of the Mongol–Okhotsk ocean. North Gobi rift magmatism extends across the Mongol–Okhotsk suture, so a plume-related origin is more consistent with available data. This plume, which would provide the heat source for magmatism in this area, explains the eastward movement of large scale magmatism over time, from the Tarim traps (300–275 Ma), through Khangai (270–240 Ma), to Khentei (230–195 Ma) in central Mongolia. [ABSTRACT FROM AUTHOR]

The Jurassic Dashibalbar granitoid pluton (~300 km2) crops out in the Triassic North-Gobi rift of central Mongolia, just south of the 230 to 195 Ma Khentei batholith. The granitoids are shallow-seated dominantly, amphibole-bearing alkali feldspar granite that contain quartz-syenite/syenite enclaves. They are all composed of megacrystic mesoperthite, quartz, Ca-Na amphibole altered to biotite and rarely with pyroxene cores, magnetite and ilmenite. The pluton yielded a concordant U-Pb zircon age of 186 ± 1 Ma, which is similar to a published 189 ± 3 Ma 40Ar/39Ar amphibole age, and indicates rapid cooling through ca. 550 °C. This age is ca. 10 my younger than the 196 ± 4 Ma age of the hi modal volcanic complex intruded by the pluton. The volcanic complex is composed of augite-phyric transitional basalt and rhyolite/ comendite. Both basalts and rhyolites/comendites are evolved within-plate varieties with positive εNd(t) (~ +2.5) values. The granitoids are evolved alkaline, A-type granites and quartz-syenites/syenites that are enriched in light REE's, but show a distinct depletion in Eu, Sr and Ba, indicative of feldspar fractionation. The data are consistent with derivation of the granites from the syenites by an assimilation-fractional crystallization process involving a silicic crustal contaminant. The granitic rocks have εNd(t) values of ~ +0.8 to +1.2, which are slightiy lower than eNd(tx values + 1.3 to +1.6 in the syenites, although both have similar TDM model ages (~800-970 Ma). The ~800 Ma model ages of the basalt and rhyolite/comendite are comparable to those of the intrusion and enclaves. The compositions of all these rocks, including εNd(t) md TDM, are within the range of A-type granites and volcanic complexes of the Early Mesozoic Mongolian-Transbaikalian igneous province. The results suggest derivation of a parent magma of the granitoids and felsic volcanic rocks from underplated, enriched, Neoproterozoic mantle-derived basaltic rocks in the lower crust, whereas the Dashibalbar basalts were derived from Neoproterozoic subcontinental lithospheric mantle; Neoproterozoic megablocks crop out in adjacent parts of the Central Asian Orogenic Belt. Melting of lower crust and subcontinental lithospheric mantle implies a rising heat source. Although such a heat source is consistent with both rifting and passage over the Mongolian mantle plume, only the latter explains the west-to-east migration of the magmatism and rifting. [ABSTRACT FROM AUTHOR]

Topographic uplifts in the central Sahara occur in the Hoggar-Aïr and Tibesti-Gharyan swells that consist of Precambrian rocks overlain by Cenozoic volcanic rocks. The swells and associated Cenozoic volcanism have been related either to mantle plumes or to asthenospheric upwelling and to partial melting due to rift-related delamination along pre-existing Pan-African mega-shears during the collision between Africa and Europe. The Cenozoic volcanic rocks in the Hoggar generally range from Oligocene tholeiitic/transitional plateau basalts, which occur in the centre of the dome, to Neogene alkali basalts characterized by a decrease in their degree of silica undersaturation and an increase in their La/Yb ratios. The alkali basaltic rocks occur mainly along the margins of the dome and typically have less radiogenic Nd and Sr isotopic ratios than the tholeiitic/transitional basalts. The geochemistry of the most primitive basaltic rocks resembles oceanic island basalt (OIB) tholeiitic – in particular high-U/Pb mantle (HIMU)-type – and is also similar to those of the Circum-Mediterranean Anorogenic Cenozoic Igneous (CiMACI) province. These characteristics are consistent with, but do not require, a mantle plume origin. Geophysical data suggest a combination of the two mechanisms resulting in a complex plumbing system consisting of (a) at depths of 250–200 km, an upper mantle plume (presently under the Aïr massif); (b) between 200 and 150 km, approximately 700 km northeastward deflection of plume-derived magma by drag at the base of the African Plate and by mantle convection; (c) at approximately 150 km, the magma continues upwards to the surface in the Tibesti swell; (d) at approximately 100 km depth, part of the magma is diverted into a low S-wave velocity corridor under the Sahara Basin; and (e) at approximately 80 km depth, the corridor is tapped by Cenozoic volcanism in the Hoggar and Aïr massifs that flowed southwards along reactivated Precambrian faults. [ABSTRACT FROM PUBLISHER]

The chemical composition and origin of the isotopically identified end-member mantle components have been difficult to describe because their melted samples - oceanic basalts - are affected by many processes such as variable degrees of partial melting. Exploratory data analysis [multidimensional scaling (MDS)] applied to ∼200 basalts from French Polynesia reveals over 100 ratios of similarly incompatible elements (SIER) that are minimally affected by these processes. Ratios from elements with dissimilar incompatibility are identified as affected by melting percentages. When basalt samples are compared simultaneously using ∼100 SIER and MDS, they organise in the same way that they would with isotopes, according to mantle component type. Applying discriminant analysis to the most extreme French Polynesia samples representing each mantle component yields preliminary discrimination diagrams that improve the description of chemical variation in the mantle. As a test of their utility and reliability, they are used to classify averages of known EM1, EM2, and HIMU basalts on oceanic islands from outside French Polynesia with reasonable success. Although they are preliminary and should be used cautiously, two of the diagrams based on large numbers of samples and ≥10 SIER can be used to screen 'unknown' basalt samples for mantle component character. They can also help test models for component origin. As an example of their application, it is shown that the EM1-like (isotopically) Shonkin Sag basaltic sill (Montana) has extreme EM1 trace-element characteristics suggesting that EM1 in the ocean basins represents Archean subcontinental lithospheric mantle, recycled into the convecting oceanic mantle. [ABSTRACT FROM AUTHOR]

Dykes of calc-alkaline lamprophyre cutting granite of the Hercynian Jebilet Massif of the Moroccan Meseta (western Morocco) contain crustal xenoliths. The xenoliths range in composition from mafic (cognate cumulates) and upper crustal granitic rocks through gneisses to middle crustal felsic granulites. SHRIMP U--Th--Pb zircon analyses of these rocks indicate that the dykes were likely intruded during Middle Triassic times (∼ 235 Ma), whereas the xenoliths contain zircons with concordant Carboniferous-Early Permian, Neoproterozoic and Palaeoproterozoic ages (280-328 Ma, c. 540-615 Ma, 700 Ma and ∼ 2000 Ma). The 280-328 Ma ages appear to record synchronous intrusive and high-grade (up to granulite facies) Variscan metamorphic events, suggesting that high-grade metamorphism may have facilitated the S-type granitic magmatism. On the other hand, the ∼ 540-615 Ma, 700 Ma and 2000 Ma ages correspond with Pan-African and Eburnian orogenic events recorded in the West African Craton. In a Triassic reconstruction, Morocco is juxtaposed against Nova Scotia (Canada), and some have proposed that the basement of the easternmost terrane (Meguma terrane) is a piece of the West African craton. However, lower crustal xenoliths from Devonian dykes (∼ 370 Ma) cutting the Meguma terrane have yielded Late Devonian, Neo- and Mesoproterozoic ages (378 Ma, 575-629 Ma, ∼ 880-1050 Ma and ∼ 1530 Ma). The presence of ∼ 1 Ga ages suggests that the basement of the Meguma terrane is Avalonian rather than West African, implying that in a Pangean reconstruction, the Rheic Ocean suture between NW Africa and Maritime Canada coincides with the Atlantic Ocean. [ABSTRACT FROM AUTHOR]

The Coronation mafic sills and associated Natkusiak flood basalts in Arctic Canada are part of the ∼723 Ma Franklin igneous events, a flood basalt and dyke swarm province that extends across the southern Arctic of North America and Greenland. Two representative sills, 70 and 25 m thick, respectively outcrop near Coronation Gulf in Nunavut. They are composed of clinopyroxene, plagioclase, olivine and Fe–Ti oxides, and have tholeiitic composition similar to the Natkusiak basalts. Their ϵNd values range between +4.2 and +5.9 and have (La/Yb)n ratios of ∼1.5–2. These rocks are mantle derived and were affected by minor crustal contamination. Compositional variations indicate that the Coronation sills have experienced extensive fractionation including flow differentiation during emplacement and show increased differentiation from, west to east, across the province, a feature similar to the Mackenzie dyke swarm. However, the Mackenzie dyke swarm and the Franklin igneous events have distinct chemical composition. The Franklin rocks are related to a mantle plume located near Victoria Island at the center of the dyke swarm and could represent an offshoot from the superplume related to the break-up of Rodinia. The absence of such dykes and sills in Siberia argues against locating Siberia against northern Laurentia in a Rodinia reconstruction. [Copyright &y& Elsevier]

Potassic silica-undersaturated mafic volcanic rocks form a minor portion of the predominantly calc–alkaline Eocene Challis–Kamloops volcanic belt, which extends from the northwestern United States into central British Columbia (Canada). Their major occurrence is in the Penticton Group in south central British Columbia, where they reach a thickness of up to 500 m and form the northwestern edge of the Montana alkaline province. These analcime-bearing rocks (∼53–52 Ma old) are typically rhomb porphyries of ternary feldspar (An28Ab52Or20). Additional phenocryst phases include clinopyroxene, analcime, phlogopite and rare olivine. The rocks are characterized by high total alkalis, particularly K2O (>4.5 wt%) as well as by a distinct enrichment of large-ion lithophile elements versus heavy rare-earth elements and high-field-strength elements. They have unusual isotopic compositions compared to most other rocks of the Challis–Kamloops belt, particularly high negative ∊Nd values and elevated but relatively uniform initial 87Sr/86Sr ratios (∼0.7065). The potassic silica-undersaturated rocks overlie Precambrian crust and lithosphere and were at least in part derived from ancient metasomatized subcontinental mantle lithosphere, which was modified in a Precambrian subduction setting. The alkaline rocks of the Challis–Kamloops belt are related to a slab-window environment. In particular, they were formed above the southern edge of the Kula plate adjacent to the Kula–Farallon slab window, whereas the Montana alkaline province situated well to the southeast was formed directly above the Kula–Farallon slab window. Upwelling of the hotter asthenospheric mantle may have been the thermal trigger necessary to induce melting of fertile and metasomatized lithospheric mantle. [Copyright &y& Elsevier]

Chemical and U–Pb isotopic analyses of metaigneous rocks in the northern Oaxacan Complex in southern Mexico indicate that they form part of two granitic–gabbroic suites intruded at ∼1157–1130 and ∼1012 Ma, which were metamorphosed under granulite facies conditions between ∼1004 and 980 Ma. Although the older suite has both within-plate and arc geochemical signatures, the arc characteristics (enrichment of La and Ce relative to Nb, Ta, and Th) are inferred to result from crustal contamination, a conclusion consistent with their negative ϵNd signatures. The younger suite is spatially associated with anorthosites (from which we were unable to acquire a protolith age), suggesting that collectively it forms part of anorthosite–mangerite–charnockite–granite (AMCG) suites. The tholeiitic nature of the mafic rocks along with the within-plate character of the felsic rocks suggests that they were intruded during extension related to either farfield backarc rifting, rifting above a slab window, or anorogenic intercontinental rifting. Potentially correlative AMCG suites are widespread in Mexico, the Grenville Province of eastern Canada and northeastern USA, and the Andean massifs of Colombia, however, Pb isotopic data most closely resemble those in South America. These data are consistent with published hypotheses that suggest Oaxaquia represents an exotic terrane derived from Amazonia. [Copyright &y& Elsevier]

The Neoproterozoic Sebkha el Melah inlier is a part of the Pan-African Trans-Saharan orogenic belt that is exposed in northwestern Africa east of the West African craton. The inlier is composed of a 4–5 km thick sequence of fine-grained marine to fluvial clastic sedimentary rocks intercalated with, and conformably overlain by, mafic lava flows and proximal volcaniclastic deposits, 600–1000 m thick. The lava flows and associated minor intrusives are mainly shoshonites. Their geochemical characteristics are indicative of subduction-related magmas and are characterized by relative depletion of Nb, Ta and Ti with respect to rare-earth elements and Th. Their positive but highly variable &epsiv;Nd values (+1–+5) are interpreted to reflect contamination of mantle-derived mafic melts (∼+6) by continental crust. It is suggested that the Sebkha el Melah shoshonitic rocks formed in a backarc or rifted arc setting. Their location, close to the Trans-Saharan suture, is interpreted to be the result of subduction erosion which removed the forearc and possibly also part of the arc. The shallow source (<60 km) for the Sebkha el Melah volcanic rocks is related to flat-slab subduction. Traced along strike to the south, the >620 Ma, Neoproterozoic volcanic suites of the Trans-Saharan belt change to typical continental, Andean margin calc-alkaline rocks in the northwestern Hoggar and an oceanic island arc complex in Mali. This may indicate that the rate of convergence of the West African craton and the Tuareg (Saharan) paleocontinent increased from south to north due to a change in the angle of convergence across the margin (oblique in the south to orthogonal in the north), resulting from the curve of the eastern margin of the West African craton that swings from N–S to NW–SE. [Copyright &y& Elsevier]

Voluminous basalts dominate a middle Tertiary bimodal volcanic assemblage in the Queen Charlotte Islands, British Columbia, Canada. These moderately enriched mid-ocean-ridge basalt (MORB-)like magmas were associated with significant crustal extension related to the subduction of the Pacific–Farallon ridge and the initiation of a slab window environment, which persisted for 35 Ma. These asthenospheric melts were derived from a low degree of melting of a heterogeneous peridotite source mainly in the spinel stability field, as inferred from fractional melting inversion calculations. The basaltic magmas in turn gave rise to both tholeiitic and calc-alkaline volcanic strata up to 3.5 km thick in local grabens. The tholeiitic basalts resemble MORB, with rare-earth element (REE) patterns ranging from slightly depleted to enriched in light REE (LREE). The calc-alkaline basaltic andesites are enriched in LREE, but are not strongly depleted in Nb. The rocks have overlapping Nd, Sr, and Pb isotopic compositions, similar to those of intraplate basalts from the adjacent northeast Pacific seamounts and Cordillera. The difference between the tholeiitic and calc-alkaline rocks is, in part, attributed to polybaric fractional crystallization of different proportions of plagioclase to mafic minerals from a similar tholeiitic magma. This marginal-basin subalkaline volcanic sequence and its genesis describe the slab window environment for the Tertiary tectonics of the western Canadian continental margin and provide a model for older combined tholeiitic and calc-alkaline volcanic successions.De grands volumes de basaltes dominent un assemblage volcanique bimodale du Tertiaire moyen dans les îles de la Reine-Charlotte (Colombie-Britannique, Canada). Ces magmas, moyennement enrichis, de type basalte de la dorsale médio-océanique (MORB) ont été reliés à une importante extension crustale associée à la subduction de la dorsale Pacifique–Farallon et au commencement d'un environnement d'ouverture de plaque qui a duré 35 Ma. Ces fusions asthénosphériques ont été dérivées de la fusion partielle d'une source de péridotite hétérogène, surtout dans le domaine de la stabilité des spinelles, tel que déduit des calculs d'inversion des fusions fractionnelles. À leur tour, les magmas basaltiques ont produit des strates volcaniques tholéiitiques et calco-alcalines qui atteignent jusqu'à 3,5 km d'épaisseur dans des graben locaux. Les basaltes tholéiitiques ressemblent aux MORB avec des patrons d'éléments des terres rares (REE) qui vont de légèrement épuisés à enrichis en éléments de terres rares légers. Les andésites basaltiques calco-alcalines sont enrichies de REE légers, mais le Nb n'est pas fortement épuisé. Les roches ont des compositions isotopiques Nd, Sr et Pb qui se chevauchent, semblables à celles des basaltes intraplaques des monts sous-marins de la Cordillère et du Pacifique NE adjacents. La différence entre les roches tholéiitiques et les roches calco-alcalines est attribuable en partie à la cristallisation fractionnelle polybarique des différentes proportions de minéraux plagioclases à mafiques provenant d'un magma tholéiitique semblable. Cette séquence volcanique, en marge d'un bassin marginal sub-alcalin, et sa genèse décrivent l'environnement d'ouverture de plaque pour la tectonique du Tertiaire de la marge continentale de l'Ouest canadien et fournit un modèle pour les séquences volcaniques calco-alcalines et tholéiitiques combinées antérieures.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The Paleozoic and early Mesozoic rocks of the Greenwood mining camp in southern British Columbia are a part of the Quesnel terrane in the eastern part of the Intermontane Belt of the Canadian Cordillera. Upper Paleozoic rocks include the Knob Hill Group composed of oceanic tholeiitic basalts (with (La/Yb)[sub n] 0.4-1.2), associated with deep ocean sedimentary rocks and serpentinites; the Attwood Group that comprises island-arc tholeiites (with (La/Yb)[sub n] 1-4 and positive ℇ[sub Nd] values), clastic sedimentary rocks and limestones; and a unit of oceanic gabbros with (La/Yb)[sub n] < 0.5. These lithologically defined units occur as tectonically emplaced slivers of oceanic crust probably produced during the closure of the Slide Mountain basin during the Permian. They are unconformably overlain by Middle Triassic calc-alkaline volcanic and sedimentary rocks of the Brooklyn Group. The Brooklyn Group volcanic rocks have characteristics of mature island-arc rocks, including (La/Yb)[sub n] 2.5-4.5 and positive ℇ[sub Nd] values. The Paleozoic rocks are crosscut by a 200 million years old granodioritic intrusion containing zircon with an Early Proterozoic inheritance age (~2.4 Ga). By inference, southern Quesnellia may have been well offshore from the ancestral North American margin in the Mississippian, in close proximity to the margin by the Middle Triassic, and contiguous with it by the Early Jurassic. It is suggested that the complex tectonic history of extension and contraction of the southern Canadian Cordillera during the post Middle Jurassic can be extended in south-central British Columbia as far back as the upper Paleozoic.Les roches du Paléozoïque et du Mésozoïque précoce du camp minier Greenwood dans le sud de la Colombie-Britannique font partie du terrane de Quesnel dans la partie est de la ceinture Intermontane de la Cordillère canadienne. Des roches du Paléozoïque supérieur comprennent le Groupe de Knob Hill composé de basaltes océaniques tholéiitiques (où (La/Yb)[sub n] 0,4-1,2) associés à des serpentinites et des roches sédimentaires océaniques profondes, le Groupe Attwood qui comprend des tholéiites d'arc insulaire (où (La/Yb)[sub n] 1-4 et des valeurs ℇ[sub Nd] positives), des calcaires et des roches sédimentaires clastiques ainsi qu'une unité de gabbros océaniques où (La/Yb)[sub n] < 0,5. Ces unités définies lithologiquement se présentent comme des échardes de croûte océanique mis en place tectoniquement et qui ont probablement été produites durant la fermeture du bassin de Slide Mountain au Permien. Des roches volcaniques et sédimentaires calco-alcalines du Groupe de Brooklyn, du Trias moyen, recouvrent les unités de façon discordante. Les volcaniques de Brooklyn ont les caractéristiques de roches d'arc insulaire mature et comprennent des valeurs (La/Yb)[sub n] 2,5-4,5 et des valeurs ℇ[sub Nd] positives. Les roches du Paléozoïque sont recoupées par une intrusion granodioritique de 200 Ma contenant du zircon provenant du Protérozoïque précoce (~2,4 Ga). Par inférence, la Quesnellia méridionale était peut-être bien au large de l'Amérique du Nord ancestrale durant le Mississippien, très proche de sa marge au Trias moyen et lui était contiguë au Jurassique précoce. On suggère que l'historique tectonique complexe de l'extension et la contraction de la Cordillère canadienne sud au cours du Jurassique post-moyen peut être étendu au centre-sud de la Colombie-Britannique aussi loin que le Paléozoïque supérieur.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Presents a study which examined isotopic and geochemical data indicating that intrusions in Cape Breton Island in Canada represent the roots of Neoproterozoic and Silurian magmatic arcs. Methods; Results.

The Terrace Mountain complex is a part of a discontinuous north-west trending belt of Eocene volcanic centres, which stretches for about 1000 km in southern and central interior British Columbia and probably extends into the northwestern United States. The 55–45 Ma chain is related to east-vergent subduction of oceanic plates under the North American continent. The volcanic rocks of the belt are mainly of calc-alkaline intermediate to felsic composition, typical of distal continental arcs. However, close to the Canada-United States border, in the Terrace Mountain volcanic complex, there are alkaline (shoshonitic) mafic and intermediate rocks with an unusual isotopic composition compared to most other rocks of the belt. These rocks, which are hosted in an extensional basin/half-graben associated with regional strike-slip faulting in a continental arc setting, have highly negative ɛ Nd (t) values, Proterozoic neodymium depleted mantle model ages and elevated initial 87Sr/86Sr ratios. The two rock units, which are >700 m thick were emplaced within a short (<1–2 Ma) magmatic episode at ~52 Ma. The older volcanic pulse was composed of basaltic trachyandesites while the younger pulse included trachyandesites. The rocks are enriched in strongly incompatible trace elements and underwent fractional crystallization. Both suites are related to a parent magma, which was sourced during extension of the Cordilleran orogen by partial melting of heterogeneous subduction-modified sub-continental lithospheric mantle composed of amphibole-phlogopite-bearing peridotite. Nd isotopic characteristics require an old LREE-enriched slab in the mantle suggesting that the source was separated from convecting mantle since the Proterozoic. • Atypical part of the Eocene volcanic belt running across interior of British Columbia. • Alkaline mafic and intermediate (shoshonitic) volcanic rocks of the complex are 52 Ma old. • The half-graben-hosted rocks were emplaced during extension within a continental arc. • The parent magmas were generated from a Proterozoic sub-continental lithospheric mantle. • The volcanic rocks represent an extension of the Wyoming-Montana alkaline province. [ABSTRACT FROM AUTHOR]

The Late Devonian Corner Bay pluton is a part of the Sitkoh alkaline plutonic complex on the Chichagof Island, southeastern Alaska, which is located in the Alexander terrane of the North American Cordillera. The intrusion, about 12 km long and 4 km wide, is composed predominantly of amphibole-biotite-bearing syenitic/ monzonitic rocks with minor alkaline gabbros and has a U-Pb zircon age of ~367 Ma interpreted as the crystallization age of the pluton. The rocks are metaluminous and have silica contents ranging from 47 to 63 wt% with a silica gap at 52–58 wt% and have high contents of alkalis, typical of shoshonitic rocks. They are rich in large-ion-lithophile elements (including Rb, Sr, Ba, U) and their isotopic composition is characterized by relatively uniform Ɛ Nd (t) values (+3.4 to +3.7), Neoproterozoic Nd depleted mantle model ages (650–700 Ma) and initial 87Sr/86Sr ratios (~0.704). The rocks were generated by fractional crystallization of alkali basaltic magma formed by partial melting of an amphibole-phlogopite-bearing peridotite of the sub-arc lithospheric mantle. The mantle-source underwent a Neoproterozoic metasomatic enrichment event and does not show a contribution from juvenile Devonian mantle indicating that rifting associated with the magma emplacement was of limited extent as it did not replace the old lithospheric mantle. Several geothermobarometers document emplacement of the parental magma at mid-crustal levels (8.5–10 kb) and polybaric crystallization from ~1200 °C to solidus. Crystallization of amphibole took place at ~880-980 °C and 2.4–5.5 kb. Subsequently the rocks underwent recrystallization (feldspars: 170 Ma – 40Ar/39Ar age) and re-equilibration (biotite: 129 Ma (40Ar/39Ar) at ~600-650 °C and 2 kb). Zircon, rutile and apatite saturation temperatures provide consistent results (~800 °C). The intrusion is a part of a metallogenic province of rare metals, which stretched across the islands in the southeastern most part of Alaska. • The Upper Devonian pluton is mainly composed of amphibole-biotite syenite • Differentiation is related to multistage crystal fractionation and multiple magma pulses • Parental magma was derived from a Neoproterozoic sub-arc lithospheric mantle • Pluton forms a NW extension of a rare metal metallogenic province of SE Alaska [ABSTRACT FROM AUTHOR]

Studies the host to ...700-630 Ma felsic and associated mafic volcanic rocks in Central Cape Breton Island in Nova Scotia, Canada, focusing on the development of the Avalonian arc in Nova Scotia. Information on the mafic rocks of central Cape Breton Island; What the mafic rocks lack; Objective of the study; Methods used to conduct the study; Results of the study.

Presents information on a study pertaining to Palaeozoic volcanism in Nova Scotia. Discussion of the occurrence of Palaeozoic volcanism; Details on types of volcanic rocks; Presentation of statistical information on the subject.

Discusses the geology and geochemistry of volcanic rocks of the Pioneer Formation in British Columbia. Triassic basalts; Tholeitic basalts; Compositional variations; Effect of melting on garnet stability field; Stratigraphy of Bridge River.

In the article, the authors present a comparison of the terrane wreck (TW) model and the in-order terrane (IOT) model that were used in the analysis of rocks and other geological formations in the New Brunswick and Newfoundland areas in Canada. Other topics include the correlative histories of sequential and pseudosynchronous accretionary orogenesis in the IOT model, and the analysis of primary oceans and secondary faulting.

We report new experimental results on radiative shocks obtained in Xenon and Argon in gas cells at two different pressures below 1 bar. These shock waves are generated by the interaction of the PALS iodine laser on a CH–Au foil with a typical velocity in the range of 50–100 km/s depending on the variable laser intensity, pressure, and gas. Attention is paid to the morphology and the dynamics of the radiative precursor over large time scales up to 30 ns, using 2D sub-picosecond visible interferometry, illustrating the complex interplay of hydrodynamic and radiation absorption for different initial conditions. The comparison between 1D and 2D simulations confirms the role played by lateral radiative losses in the ionization wave and the necessity of state-of-the-art integrated opacities. This study is complemented by the first XUV analysis of the shock emission between 5 and 20 nm obtained with a grating spectrometer, with line identification, which is compatible with the ionization stages deduced from interferometry and simulations. [ABSTRACT FROM AUTHOR]

Understanding the development of island arcs that accreted to the North American craton is critical to deciphering the complex geological history of the Canadian Cordillera. In the case of the Hazelton arc (part of the Stikine terrane, or Stikinia) in northwestern British Columbia, understanding arc evolution also bears on the formation of spatially associated porphyry Cu-Au, epithermal, and volcanogenic massive sulfide deposits. The Hazelton Group is a regionally extensive, long-lived, and exceptionally thick Upper Triassic to Middle Jurassic volcano-sedimentary succession considered to record a successor arc that was built upon the Paleozoic and Triassic Stikine and Stuhini arcs. In central Stikinia, near Terrace, British Columbia, the lower Hazelton Group (Telkwa Formation) comprises three volcanic-intrusive complexes (Mt. Henderson, Mt. O'Brien, and Kitselas) that, at their thickest, constitute almost 16 km of volcanic stratigraphy. Basal Telkwa Formation conglomerates and volcanic rocks were deposited unconformably on Triassic and Paleozoic arc-related basement. New U-Pb zircon ages indicate that volcanism initiated by ca. 204 Ma (latest Triassic). Detrital zircon populations from the basal conglomerate contain abundant 205-233 Ma zircons, derived from regional unroofing of older Triassic intrusions. Eleven kilometres higher in the section, ca. 194 Ma, rhyolites show that arc construction continued for >10 million years. Strata of the Nilkitkwa Formation (upper Hazelton Group) with a U-Pb zircon age of 178.90 ± 0.28 Ma represent waning island-arc volcanism. Telkwa Formation volcanic rocks have bimodal silica concentrations ranging from 48.1 to 62.8 wt.% and 72.3 to 79.0 wt.% and display characteristics of subduction-related magmatism (i.e., calc-alkaline differentiation with low Nb and Ti and high Th concentrations). Mafic to intermediate rocks form a differentiated suite that ranges from high-Al basalt to medium- to high-K andesite. They were derived from hydrous melting of isotopically juvenile spinel lherzolite in the mantle wedge and from subsequent fractional crystallization. Compared to basalts and andesites (εNd = +5 to +5.5), rhyolites have higher positive εNd values (+5.9 to +6.0) and overlapping incompatible element concentrations, indicating that they are not part of the same differentiation suite. Rather, the rhyolites formed from anatexis of arc crust, probably caused by magmatic underplating of the crust. This study documents a temporal and spatial co-occurrence of Hazelton Group volcanic rocks with a belt of economic Cu-Au porphyry deposits (ca. 205-195 Ma) throughout northwestern Stikinia. The coeval relationship is attributed to crustal underplating and intra-arc extension associated with slab rollback during renewed or reconfigured subduction beneath Stikinia, following the demise of the Stuhini arc in the Late Norian. [ABSTRACT FROM AUTHOR]

Abstract: Microgranular enclaves are common within intermediate to felsic granitic rocks that have I- and S-type affinity however they are rare within alkaline anorogenic granitoids of A-type affinity. The Permian (~260Ma) Emeishan large igneous province (ELIP) of southwest China contains two peralkaline silica saturated A-type granitic plutons that host microgranular enclaves. The enclaves from the Baima pluton are intermediate in composition and have lower SiO2 and higher TiO2, CaO and Mg# (SiO2 =57.2 to 63.0wt.%; TiO2 =0.8 to 1.8wt.%; CaO=1.7 to 3.3wt.%; Mg#=28 to 44) than their host (SiO2 =62.6 to 67.8wt.%; TiO2 =0.5 to 1.4wt.%; CaO=0.4 to 1.8wt.%; Mg#=15 to 31). The enclaves from the Taihe pluton are more felsic (SiO2 =63.8 to 71.3wt.%; TiO2 =0.3 to 0.6wt.%; CaO=0.6 to 2.3wt.%; Mg#=8 to 22) but are still less evolved than their host (SiO2 =69.8 to 75.1wt.%; TiO2 =0.2 to 0.6wt.%; CaO=0.4 to 0.8wt.%; Mg#=3 to 12). In both cases, the enclaves have very similar εNd(T) values (Baima εNd(T) =+2.8 to +3.2; Taihe εNd(T) =+1.0 to +2.0) as their hosts (Baima εNd(T) =+3.0 to +3.2; Taihe εNd(T) =+1.5 to +1.9). The major and trace element trends of the enclave-host pairs suggest that fractional crystallization occurred and that element diffusion was likely minimal. The enclaves are interpreted as entrained accumulations of early formed crystals of a silicic magma which was originally produced by fractional crystallization of a mafic magma. [Copyright &y& Elsevier]

The Liscomb Complex comprises Late Devonian intrusive rocks (principally peraluminous granite) and medium- to high-grade metamorphic rocks (“gneisses”) that collectively are hosted by low-grade (greenschist facies) metasediments of the Cambro-Ordovician Meguma Group. The conventional view that these “gneisses” contain high-grade mineral assemblages and represent basement rocks has recently been challenged, and indeed, some of the rocks previously mapped as gneisses, particularly metapelites, have isotopic compositions resembling the Meguma Group. Amphibole-bearing enclaves in the Liscomb plutons, however, are isotopically distinct and in this regard resemble xenoliths of basement gneisses in the Popes Harbour lamprophyre dyke, south of the Liscomb area. Metasedimentary enclaves with Meguma isotopic signatures can contain garnets with unzoned cores (implying high temperatures) that host high-grade minerals (prismatic sillimanite, spinel, and (or) corundum) and are enclosed by retrograde-zoned rims. These features are interpreted here as having formed during and following the attainment of peak temperatures related to Liscomb magmatism. The amphibole-bearing meta-igneous rocks described here contain cummingtonite or hornblendic amphibole and occur as enclaves in granodioritic to tonalitic plutons. They are mineralogically, texturally, and isotopically distinct from Meguma metasediments and at least some of the plutonic rocks that enclose them, so remain the most likely candidate for basement rocks in the Liscomb Complex. Le complexe de Liscomb comprend des roches intrusives du Dévonien tardif (surtout un granite hyperalumineux) et des roches ayant subi un métamorphisme de moyenne à forte intensité (des gneiss) qui, collectivement, se retrouvent dans des métasédiments de faible métamorphisme (faciès des schistes verts) du Groupe de Meguma (Cambrien-Ordovicien). L’explication classique que les « gneiss » contiennent des assemblages minéralogiques de métamorphisme intense a récemment été contestée; en effet, quelques roches, auparavant classées en tant que gneiss, surtout des métapélites, ont des compositions isotopiques qui ressemblent à celles Groupe de Meguma. Dans les plutons Liscomb, des enclaves comportant des amphiboles sont toutefois isotopiquement distinctes et, à ce titre, elles ressemblent aux xénolites des gneiss de socle dans le dyke de lamprophyre de Popes Harbour, au sud de la région de Liscomb. Des enclaves métasédimentaires portant les signatures isotopiques Meguma peuvent contenir des grenats à noyau sans zonation (indiquant des températures élevées) qui contiennent des minéraux indicateurs de métamorphisme intense (sillimanite prismatique, spinelle et (ou) corindon) et qui sont entourés de bordures rétromorphosées. Ces caractéristiques auraient été formées durant et après l’atteinte de températures de crête associées au magmatisme Liscomb. Les roches méta-ignées comportant des amphiboles et décrites dans cet article contiennent de la cummingtonite ou une amphibole à hornblende et se retrouvent en tant qu’enclaves dans des plutons granodioritiques à tonalitiques. Des points de vue minéralogique, textural et isotopique, ces roches ignées sont distinctes des métasédiments Meguma et au moins une partie des roches plutoniques hôtes; elles demeurent donc les meilleures candidates pour les roches du socle dans le complexe de Liscomb. [ABSTRACT FROM AUTHOR]

Alpha-melanocyte stimulating hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH) possess properties suggesting that they may be involved in the pathogenesis of restless legs syndrome (RLS). We sought to determine if alpha-MSH and ACTH when administered centrally in rat recapitulate features reminiscent of RLS: increased activity, sleep fragmentation, and periodic movements during sleep. Rats were instrumented with electroencephalography, electromyography, and intracerebral cannulae and recorded for the measurement of sleep, periodic movements, and behavior following intracerebroventricular administration of alpha-MSH, ACTH, or saline. Studied behavior included grooming, locomotion, and rearing during wake and limb movements during sleep. Vigilance states included active wake (AW), quiet wake (QW), slow wave sleep I (SWSI), slow wave sleep II (SWSII), and paradoxical sleep (PS). All rats received normal saline acting as their own controls. Different rats received alpha-MSH in doses of 0.05, 0.5, 1.0, 2.0, and 6.0 microg or ACTH in doses of 0.5, 1.0, and 2.0 microg. Administered alpha-MSH caused an increase in waking behavior and prolongation of sleep latency, while ACTH stimulated waking behavior and fragmented sleep, yielding more AW and less SWSII and PS. Both hormones increased periodic movements during sleep. When administered centrally in rat, alpha-MSH and ACTH stimulate motor activity in wake, cause changes in sleep architecture, and increase periodic movements in sleep. These melanocortin hormones may play a role in the pathogenesis of RLS. [ABSTRACT FROM AUTHOR]

Expanding laser plasmas, produced by high energy laser radiation, possess both high thermal and magnetic field energy densities. Characterization of such plasma is challenging but may provide essential information needed for understanding its physical behavior. Among the standard experimental techniques used for plasma diagnostics, conventional interferometry is one of the most convenient, informative, and accurate. Attempts to extract more information from each laser shot on large facilities have led to development of complex interferometry, which allows us to reconstruct both plasma electron density and magnetic field distributions from a single data object. However, such a benefit requires more accurate processing, critically important in some situations. This work focuses on quasi-axisymmetric interaction geometry. Starting from basic principles, we present a general analysis, consider main error sources, and obtain plasma density and magnetic field distributions with their derived error bars. A regularization procedure, significantly decreasing an error near the plasma symmetry axis, is proposed and analyzed in detail. With use of synthetic datasets, the presented analysis is generally universal for quasi-axisymmetric plasmas. [ABSTRACT FROM AUTHOR]

Multidimensional modeling of phenomena and processes occurring during the expansion of the laser-produced plasma for different irradiation conditions related to both the laser beam parameters and the target constructions is a very complex issue, especially when modeling requires consideration of kinetic processes associated with the development of various types of microscopic instability. Multidimensional PIC codes create such a possibility, but their use is limited to modeling phenomena even in a very narrow timescale due to the limited computational capabilities of current supercomputers. For this reason, the paper attempts to interpret the results of the spontaneous magnetic field (SMF) measurements obtained during the PALS (Prague Asterix Laser System) experiment [Pisarczyk et al., AIP Adv. 10, 115201 (2020); Pisarczyk et al., Phys. Plasmas 22, 102706 (2015)] based on the 2D magneto-hydrodynamic (MHD) model [Jach et al., Computer Modeling of Dynamic Interaction of Bodies by Free Point Method (PWN, Warsaw, 2011)]. The MHD equations were used with included arbitrary (i) current of hot electrons treating it as an additional external current and (ii) ion-sound instability responsible for the increase in anomalous resistance in areas with high temperature and low-density plasma. The spatial distribution of magnetic fields and current density obtained from 2D modeling are in acceptable agreement with the experimental results [Pisarczyk et al., Plasma Phys. Controlled Fusion 62, 115020 (2020); Zaraś-Szydłowska et al., AIP Adv. 10, 115201 (2020); Pisarczyk et al., Phys. Plasmas 22, 102706 (2015)]. The inclusion of temporal changes in anomalous resistance in modeling allowed us to explain the persistence of high SMF amplitude at the level of several megagauss after the laser pulse ended due to the effect of magnetic field freezing. [ABSTRACT FROM AUTHOR]

This paper describes design, development, and implementation of a multi-channel magnetic electron spectrometer for the application in laser–plasma interaction experiments carried out at the Prague Asterix Laser System. Modular design of the spectrometer allows the setup in variable configurations to evaluate the angular distribution of hot electron emission. The angular array configuration of the electron spectrometers consists of 16 channels mounted around the target. The modules incorporate a plastic electron collimator designed to suppress the secondary radiation by absorbing the wide angle scattered electrons and photons inside the collimator. The compact model of the spectrometer measures electron energies in the range from 50 keV to 1.5MeV using ferrite magnets and from 250 keV to 5MeV using stronger neodymium magnets. An extended model of the spectrometer increases the measured energy range up to 21MeV or 35MeV using ferrite or neodymium magnets, respectively. Position to energy calibration was obtained using the particle tracking simulations. The experimental results show the measured angularly resolved electron energy distribution functions from interaction with solid targets. The angular distribution of hot electron temperature, the total flux, and the maximum electron energy show a directional dependence. The measured values of these quantities increase toward the target normal. For a copper target, the average amount of measured electron flux is 1.36 × 1011, which corresponds to the total charge of about 21 nC. [ABSTRACT FROM AUTHOR]

Laser plasma created by intense light interaction with matter plays an important role in high-energy density fundamental studies and many prospective applications. Terawatt laser-produced plasma related to the low collisional and relativistic domain may form supersonic flows and is prone to the generation of strong spontaneous magnetic fields. The comprehensive experimental study presented in this work provides a reference point for the theoretical description of laser-plasma interaction, focusing on the hot electron generation. It experimentally quantifies the phenomenon of hot electron retention, which serves as a boundary condition for most plasma expansion models. Hot electrons, being responsible for nonlocal thermal and electric conductivities, are important for a large variety of processes in such plasmas. The multiple-frame complex-interferometric data providing information on time resolved spontaneous magnetic fields and electron density distribution, complemented by particle spectra and x-ray measurements, were obtained under irradiation of the planar massive Cu and plastic-coated targets by the iodine laser pulse with an intensity of above 1016 W cm−2. The data shows that the hot electron emission from the interaction region outside the target is strongly suppressed, while the electron flow inside the target, i.e. in the direction of the incident laser beam, is a dominant process and contains almost the whole hot electron population. The obtained quantitative characterization of this phenomenon is of primary importance for plasma applications spanning from ICF to laser-driven discharge magnetic field generators. [ABSTRACT FROM AUTHOR]

Generation of spontaneous magnetic fields (SMFs) is one of the most interesting phenomena accompanying an intense laser–matter interaction. One method of credible SMFs measurements is based on the magneto-optical Faraday effect, which requires simultaneous measurements of an angle of polarization plane rotation of a probe wave and plasma electron density. In classical polaro-interferometry, these values are provided independently by polarimetric and interferometric images. Complex interferometry is an innovative approach in SMF measurement, obtaining information on SMF directly from a phase–amplitude analysis of an image called a complex interferogram. Although the theoretical basis of complex interferometry has been well known for many years, this approach has not been effectively employed in laser plasma research until recently; this approach has been successfully implemented in SMF measurement at the Prague Asterix Laser System (PALS). In this paper, proprietary construction solutions of polaro-interferometers are presented; they allow us to register high-quality complex interferograms in practical experiments, which undergo quantitative analysis (with an original software) to obtain information on the electron density and SMFs distributions in an examined plasma. The theoretical foundations of polaro-interferometric measurement, in particular, complex-interferometry, are presented. The main part of the paper details the methodology of the amplitude–phase analysis of complex interferograms. This includes software testing and examples of the electron density and SMF distribution of a laser ablative plasma generated by irradiating Cu thick planar targets with an iodine PALS laser at an intensity above about 1016 W/cm2. [ABSTRACT FROM AUTHOR]

The laser-induced Cavity Pressure Acceleration (CPA) scheme [S. Borodziuk et al., Appl. Phys. Lett. 95, 231501 (2009)] allows for effective transformation of the laser energy into the kinetic energy of plasma streams and dense plasma objects. It has been proven that using long-wavelength laser beams, with relatively low energies (up to 500 J for λ1 = 1.315 µm and FWHM = 350 ps), it is possible to accelerate macroparticles to very high velocities (above 107 cm/s). The study of neutron yield showed the benefit of CPA in delivering ion temperatures and density sufficient to reach the thermonuclear region. [ABSTRACT FROM AUTHOR]

We present the results of an experiment on laser-driven shock waves performed at the Prague Asterix Laser system (PALS), where the fundamental frequency of the laser (1315 nm) is used to launch a strong shock in planar geometry. The experiment aims to characterize both shock waves and hot electrons generated at intensities of ≃ 10 16 W / cm 2 . It is shown that, in these interaction conditions, hydrodynamics is strongly impacted by noncollisional mechanisms, and the role of the hot electrons, generated by parametric instabilities, is essential in determining shock dynamics. [ABSTRACT FROM AUTHOR]

The first space-time resolved spontaneous magnetic field (SMF) measurements realized on Prague Asterix Laser System are presented. The SMF was generated as a result of single laser beam (1.315 lm) interaction with massive planar targets made of materials with various atomic numbers (plastic and Cu). Measured SMF confirmed azimuthal geometry and their maximum amplitude reached the value of 10 MG at the laser energy of 250 J for both target materials. It was demonstrated that spatial distributions of these fields are associated with the character of the ablative plasma expansion which clearly depends on the target material. To measure the SMF, the Faraday effect was employed causing rotation of the vector of polarization of the linearly polarized diagnostic beam. The rotation angle was determined together with the phase shift using a novel design of a two-channel polaro-interferometer. To obtain sufficiently high temporal resolution, the polarointerferometer was irradiated by Ti:Sa laser pulse with the wavelength of 808 nm and the pulse duration of 40 fs. The results of measurements were compared with theoretical analysis. [ABSTRACT FROM AUTHOR]

A comparative study of photoionized plasmas created by two soft X-ray and extreme ultraviolet (SXR/EUV) laser plasma sources with different parameters is presented. The two sources are based on double-stream Xe/He gas-puff targets irradiated with high (500 J/0.3 ns) and low energy (10 J/ 1 ns) laser pulses. In both cases, the SXR/EUV beam irradiated the gas stream, injected into a vacuum chamber synchronously with the radiation pulse. Irradiation of gases resulted in formation of photoionized plasmas emitting radiation in the SXR/EUV range. The measured Ne plasma radiation spectra are dominated by emission lines corresponding to radiative transitions in singly charged ions. A significant difference concerns origin of the lines: K-shell or L-shell emissions occur in case of the high and low energy irradiating system, respectively. In high energy system, the electron density measurements were also performed by laser interferometry, employing a femtosecond laser system. A maximum electron density for Ne plasma reached the value of 2·1018cm-3. For the low energy system, a detection limit was too high for the interferometric measurements, thus only an upper estimation for electron density could be made. [ABSTRACT FROM AUTHOR]

Abstract: The Sand Bay and Lighthouse (Lower- and Upper-) and Armer Bay gneiss associations comprise metasupracrustal rocks within, respectively, the Shawanaga and basal Parry Sound domains – elements of deep-crustal thrust sheets of the Central Gneiss Belt of the Grenville Province in Ontario. New and published geochemical, isotope and detrital zircon data for metavolcanic and metasedimentary rocks of these gneiss associations suggest origin in one or more late Mesoproterozoic Laurentian margin back-arcs. Mean ɛ Nd values for the Sand Bay, Lower- and Upper Lighthouse gneiss associations and the Armer Bay metavolcanic amphibolites are, with the exception of Sand Bay, close to DM values for their estimated time of eruption (+2.8, +5.6, +5.0 and +4.2 respectively). Taken in conjunction with extant and new geochemical analyses and field relations these data are compatible with protoliths of all the units originating in rifted arcs or back-arcs deposited on thin (Sand Bay, Armer Bay) to vanishingly thin (Lighthouse) pre-existing crust. Detrital zircon data indicate the Sand Bay units are younger than ca. 1260Ma. The Lower Lighthouse unit formed after ca. 1234Ma and metasediments close to the base of the Upper Lighthouse gneiss association formed at or after ca. 1350Ma, whereas deposition age at the top of the unit is estimated at less than ca. 1249Ma. A metasediment layer within the Armer Bay amphibolites has detrital ages clustered at 1251Ma, similar to the Upper Lighthouse metasediments. A quartz rich metasediment from the top of Armer Bay gneiss association is estimated to have a maximum age of deposition of ca. 1322Ma. The units represent one or more rifting events of the Andean-type Laurentian margin in a post 1.35Ga episode(s) distinct from that documented in the Muskoka-Ojibway arc at 1.45Ga. As such they may be the tectonically reworked equivalents of rifted arcs and back-arcs related to Parry Sound domain arc(s) and related to magmatic units of similar age in the Composite Arc Belt. [Copyright &y& Elsevier]

The Campamento Au/Ag deposit located within Linear Gold's Ixhuatán project was discovered in June 2004. It is located in the state of Chiapas, southern Mexico. The deposit is situated in a sequence of highly fractured Pleistocene-Pliocene andesitic volcanic rocks intruded by a complex feldspar porphyry. Campamento is a high-grade, gold-silver deposit situated at or near the surface. It has a resource estimate of 1.0 million ounces of gold, 4.4 million ounces of silver in the measured and indicated categories, and 0.7 million ounces of gold and 2.3 million ounces of silver in the inferred category, all at a cut-off of 0.50 grams per tonne gold. Previous work on the deposit by Linear Gold has indicated that the deposit shows upper porphyry to epithermal style of Au/Ag deposition. To further evaluate the deposit, the Portable Infrared Mineralogical Analyzer (PIMA) was used. This is a technique that has been recently applied in the exploration industry. It can detect energy generated by vibrations within molecular bonds that show bending and stretching modes with the 1.3-2.5 µm interval. The spectra collected are analyzed for many alteration minerals and mineral combinations specific to various ore deposits. No sample preparation is required and it can identify alteration clay minerals on site faster than the conventional x-ray diffraction method. The results from the Campamento PIMA survey show the zoning of temperature sensitive clay minerals (smectite, interstratified illite/smectite, illite, biotite, and muscovite). The appearance of the higher temperature minerals biotite and muscovite on the surface implies a lowering of the paleo-surface by approximately 725-1200 m. In addition, the PIMA data also indicates telescoping of alteration assemblages suggesting high rates of erosion or a sector collapse during the formation of the deposit. [ABSTRACT FROM AUTHOR]

Abstract: The origin and age of high pressure (HP) rocks are crucial for paleogeographic reconstructions because they either define an oceanic suture or an extrusion zone within the upper plate. HP rocks in the San Miguel Las Minas area in the northern part of the Acatlán Complex, southern Mexico have been inferred to be of early Paleozoic age and to mark oceanic sutures. However, blueschists in the northern part of the complex have yielded Mississippian 40Ar/39Ar plateau ages of 344±5Ma for glaucophane and 338±3Ma and 337±2Ma for muscovite. These ages are slightly younger than recently published ages: a U–Pb zircon age of 353±1Ma from associated eclogite, and a 347±3Ma muscovite age from the tectonically overlying, greenschist facies Las Minas Unit. Taken together, these data indicate rapid cooling between 700° and 340°C in ca. 17Myr. On the other hand, associated Ordovician Anacahuite Amphibolite cooled through ca. 500°C at 299±6Ma (40Ar/39Ar on hornblende) suggesting a second, Permian phase of exhumation. Protoliths of the high grade rocks include Cambrian–Ordovician, rift-passive margin, psammites, pelites, and tholeiitic dykes, an Ordovician mafic intrusion (Anacahuite Amphibolite dated at 470±10Ma: U–Pb zircon) and megacrystic granite (dated at 492±12Ma: U–Pb zircon), and arc-related mafic rocks of unknown age. These rocks are interpreted to have been part of the upper plate rocks that was removed by subduction erosion and taken to depths between 35 and 55km where they underwent blueschist–eclogite facies metamorphism. This was followed by rapid extrusion along a channel bounded by an easterly dipping, Mississippian, listric normal shear zone, and a thrust modified by a Permian dextral fault. Rocks above and below the extrusion zone are mainly Cambro-Ordovician rift-passive margin units, but a small vestige of the arc is preserved as dikes cutting rocks lying unconformably beneath the fossiliferous latest Devonian–Lower Permian Patlanoaya Group. Since faunal data indicate that Pangea had begun amalgamation by the Mississippian, at which time the Acatlán Complex lay 1500–2000km south of the Ouachita collisional orogen between Gondwana and Laurentia, it is inferred that subduction and extrusion of the high pressure rocks occurred on the active western margin of Pangea. [Copyright &y& Elsevier]