A two-dimensional (2-D) array (4 by 8) of single-photon avalanche diodes integrated in an industrial complementary metal-oxide-semiconductor (CMOS) process is presented. Each pixel combines a ...photodiode biased above its breakdown voltage in the so-called Geiger mode, a quenching resistor, and a simple comparator. The pitch between the pixels is 75 μm and the diameter of each pixel is 6.4 μm. The full integration allows reducing the number of charge carriers in a Geiger pulse. The electroluminescence responsible for optical crosstalks between pixels is then reduced leading to a negligible optical crosstalk probability. Thanks to the cleanness of the fabrication process, no afterpulsing effects are noticed. At room temperature, most of the pixels exhibit a dark-count rate of about 50 Hz. The detection probability is almost identical for all 32 pixels of the array with relative variation in the range of a few percents. This letter demonstrates the feasibility of an array of single-photon detectors sensitive in the visible part of the spectrum. Besides low production costs and compactness, an undeniable benefit lies in the potential to easily modify the design to fit a specific application. Furthermore, the CMOS integration opens the way to on-chip data processing.
This paper presents data on the geological position, geochemistry, age, and isotopic characteristics of the granitoids of the southern part of the Voznesenka terrane, Southern Primorye ...(Muraviev–Amursky Peninsula and its vicinities). All of the studied granitoids were formed in three stages: the Ordovician, Silurian, and Permian. The Silurian and Permian ages of the granitoid intrusions have been previously determined (Ostrovorussky Massif, 432–422 Ma, and 250 ± 4 Ma, early and late associations, respectively; Sedanka massif, 261 ± 3 Ma). The granites of the Artem and Nadezhdinsky massifs define an U–Pb zircon age of 481 ± 6 and 452 ± 4 Ma, respectively. The geochemical and isotope data show mainly the crustal nature of the granitoids. Their formation was related to melting of relatively immature rocks of the continental crust (mafic–intermediate volcanic rocks). The Nd isotope composition of the granitods (TNd(DM–2) = 1.3 Ga) indicates the absence of the mature ancient crust at the basement of the southern Voznesenka terrane. The maximum contribution of mantle sources to the granite formation is recorded in the Permian associations. A comparison of the peaks of intrusive magmatism in the southern part of the Voznesenka terrane and adjacent territories suggests that the formation of the granitoids of the Muraviev–Amursky Peninsula and its vicinities was caused by the interaction of continental blocks with two oceanic basins: the Paleoasian (and its fragments) and Paleopacific ones.
This paper reports Rb–Sr and Sm–Nd isotope data on the gabbro–diorite–tonalite rock association of the Reft massif (eastern margin of the Middle Urals) and Lu–Hf isotope data on zircon populations ...from these rocks. In terms of Nd and Hf isotope composition, the rocks of the studied association are subdivided into two distinctly different groups. The first group consists of gabbros and diorites, as well as plagioclase granites from thin dikes and veins cutting across the gabbros. In terms of
43
Nd/
144
Nd
i
= 0.512518–0.512573 (ε
Nd
(T) = +8.6...+9.7) and
176
Hf/
177
Hf
i
= 0.282961–0.283019 (ε
Hf
(T) = +15.9...+17.9), these rocks are practically identical to depleted mantle. Their Nd and Hf model ages show wide variations, but in general are close to their crystallization time. The second group is represented by tonalites and quartz diorites, which compose a large body occupying over half of the massif area. These rocks are characterized by the lower values of
143
Nd/
144
Nd
i
= 0.512265–0.512388 (ε
Nd
(T) = +3.7...+6.0) and
176
Hf/
177
Hf
i
= 0.282826–0.282870 (ε
Hf
(T) = +11.1...+12.7). The T
DM
values of the second group are much (two–three times) higher than their geological age (crystallization time), which indicates sufficiently long crustal residence time of their source. The initial
87
Sr/
86
Sr in the rocks of both the groups varies from 0.70348 to 0.70495. This is likely explained by the different saturation of melts with fluid enriched in radiogenic Sr. The source of this fluid could be seawater that was buried in a subduction zone with oceanic sediments and released during slab dehydration. Obtained data make it possible to conclude that the formation of the studied gabbro–diorite–tonalite association is a result of spatially and temporally close magma formation processes in the crust and mantle, with insignificant contribution of differentiation of mantle basite magma.
Research subject.
In this research, we carried out Sm-Nd- и Rb-Sr-dating of pyrochlore carbonatite from the Vishnevogorsky niobium deposit, Ilmeno-Vishnevogorsky Alkaline Complex, Southern Urals. IVC ...is located in the Ural fold region and is a carbonatite complex of the linear type. Rare metal (Nb-Zr-TR) deposits and occurrences are related to IVC. The age and the duration of IVC deposits formation remains a matter of debate. To determine the age of IVC carbonatites and related niobium ore, we measured Sm-Nd and Rb-Sr isotopic compositions and concentrations of the elements in the minerals (pyrochlore, calcite, apatite, biotite) and bulk sample of pyrochlore carbonatite.
Materials and methods.
The Sm and Nd isotopic compositions and concentrations were determined on a Finnigan MAT-262L (RPQ) seven-collector mass spectrometer in the static regime at the Geological Institute of the Kola Scientific Center, Apatity, Russia. The Sr and Rb isotopic compositions and concentrations were determined on thermos-ionization mass spectrometer Triton Plus (“Geoanalitik”, IGG UD RAN, Ekaterinburg, Russia).
Results.
Age of pyrochlore carbonatites from ore zone 140 (Vishnevogorsky deposit, IVC) defined by Sm-Nd and Rb-Sr isotopic methods. Mineral Sm-Nd-isochron (5 points) indicated age 229 ± 16 Ma, mineral Rb-Sr-isochron (5 points) showed similar age 250.5 ± 1.2 Ma.
Conclusions.
Results Sm-Nd и Rb-Sr dating indicate that the pyrochlore сarbonatites of ore zone 140 crystallized ≈ 250 Ma ago, at the stage of the postcollisional extension, possibly, in connection with exhumation complex, which was accompanied by decompression, partial melting of rocks, involving fluids, dissolution and precipitation of Ordovician-Silurian alkaline-carbonatitе complex. Thus, the formation of the IVC carbonatites and related Nb-ore, which began in Silurian (S), continued in Permian (P) and Triassic (T1-2) and was associated with the post-collision stage of tectonic activity in the Ural Fold Belt.
We study variations in the dielectric properties of a semi-insulating Gallium arsenide (GaAs) wafer under millisecond pulses of extreme subterahertz power density of up to 180 kW/mm2 at 263 GHz. ...Increasing the duration and power of the pulse, we have obtained sequential down- and upshifts within the range of more than two orders in the effective loss tangent of the wafer in experiments. We have observed the existence of an optimal regime of subterahertz irradiation, in which the accurate, simple and selective annealing of the wafer from the 300 nanometer-thick surface layer of oxides is achieved, even in plain air, without a damage to pure GaAs. An finite-difference time-domain-based numerical simulation explains such selectivity with a difference in tangent losses of about 25 times between pure GaAs and its impurities in the subterahertz band.
The first Sm/Nd and .sup.40Ar/.sup.39Ar isotope-geochronological studies of amphibolite of the Khanmeikhoi Formation of the Kharbei metamorphic complex (Kharbei Block, Polar Urals) showed that ...metamorphism reaching the conditions of the amphibolite facies of moderate and high pressures occurred in the Devonian (367 ± 40 Ma (amphibole, plagioclase, whole rock), 392 ± 23 Ma (amphibole, garnet, whole rock), Sm/Nd method) and is consistent with the age estimates of high-pressure and regressive metamorphism within the Marunkeu Block. They correspond to the stage of radical restructuring of subduction processes that began in the Silurian to the east of the Baltica, associated with the subduction of the paleocontinent edge beneath the island arc and wedging of the subduction zone. The regressive stage and the beginning of the exhumation of the Kharbei metamorphic complex occurred in the Early Carboniferous (346 ± 5 Ma, amphibole, .sup.40Ar/.sup.39Ar method). Judging from the model age of amphibolite (Т(DM2) of 1.07 and 1.13 Ga) corresponding to the Middle-Late Riphean boundary, the Khanmeikhoi Formation is not older than that time.
New U–Pb and Sm–Nd isotope data have been obtained in the Kandalaksha–Kolvitsa zone, Baltic Shield, on accessory zircon and rutile, along with whole-rock and secondary metamorphic minerals. Isotope ...U–Pb age of single zircon grains from metagabbro of the Kandalaksha Anorthosite Massif is 2453.5 ± 4.8 Ma, which is close to the U–Pb age of zircon from the Kolvitsa Massif metagabbro (2448 ± 5 Ma). For the first time, REEs in zircon grains of the Kandalaksha metagabbro have been analyzed and the results have been plotted. Ti-in-zircon thermometry has been applied using LA–ICP–MS: it yielded an average temperature of zircon crystallization of 844°C. The isotope and geochemical new data obtained indicate a magmatic genesis of the zircon crystals studied.
Late Vendian (540–550 Ma) U–Pb age was established for zircon from postcollisional granites of the Osinovsky Massif located among island-arc complexes of the Isakovka terrane in the northwestern ...Sayan–Yenisei accretionary belt. The granites were formed 150 Ma after the formation of the host island-arc complexes and 50–60 Ma after the beginning of their accretion to the Siberian Craton. These events mark the final stage of the Neoproterozoic history of the Yenisei Ridge related to the end of accretion of oceanic fragments and the beginning of the Caledonian Orogeny. The granites are subalkaline leucoractic Na–K rocks enriched in Rb, U, and Th. The petrogeochemical and Sm–Nd isotope data (T
Nd
(DM)-2st = 1490–1650 Ma and ε
Nd
(T) from–2.5 to–4.4) indicate that their source was highly differentiated continental crust of the SW margin of the Siberian Craton. Therefore, the host Late Riphean island-arc complexes were thrust over the craton margin for distance significantly exceeding the size of the Osinovsky Massif.
In the Trollfjord–Rybachy–Kanin fault zone, the major convergent suture between the East European and West Arctic platforms, on the isthmus of Cape Vestnik located between the Sredny and Rybachy ...peninsulas, in the Riphean terrigenous sequence, massifs of disintegrated granitoids have been identified, primarily belonging to the Archean crystalline basement and which subsequently underwent tectonic extrusion to the upper horizons in the form of protrusions. Petrographic studies of disintegrated rocks from the Vestnik granitoid massif and the surrounding rocks indicate their high permeability and porosity in shattering zones. The positive Eu anomaly and decrease in content of light rare earth elements indicates the reducing nature of the fluids that affected disintegrated rocks, contributing to their formation under decompression conditions. The buried massifs of disintegrated granites may have reservoir properties. U–Pb and Sm–Nd isotopic studies of disintegrated plagiogranites with a model age of 2966 Ma has made it possible to correlate them with the rocks from the Murmansk block of the Baltic Shield. According to Sm–Nd data, the dolerite dike that cuts the plagiogranite massif has an age of 1333 ± 160 Ma (Middle Riphean) on pyrite and plagioclase, which corresponds to fragmentation of the basement at the initial continental rifting stage, which led to the formation of the White Sea paleorift system. East of Cape Vestnik, within the water area of the Barents Sea, a chain of linear–arched contrasting negative anomalies has been recorded in the gravity field. They are interpreted with high probability as reflections of the plate-shaped massifs of disintegrated granitoids included in the Riphean sedimentary sequence along the Trollfjord–Rybachy–Kanin shear zone, which may suggest a promising hydrocarbon potential of this zone under certain conditions.
The article provides new Sm-Nd and Nd-Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. The isotope Sm-Nd dating on metamorphic ...minerals (apatite, garnet, sulfide) and rock of the Kolvitsa massif yielded the age of 1887±37 Ma (high-temperature metasomatic transformation) and 1692±71 Ma (regional fluid processing). The model Sm-Nd age of metagabbro is 3.3 Ga with a negative value of εNd=-5.5, which indicates processes of crustal contamination or primary enriched mantle reservoir of initial magmas. According to geochronological and Nd-Sr isotope data, rocks of the Kandalaksha-Kolvitsa complex seem to have a common anomalous mantle source with Paleoproterozoic layered intrusions in the Baltic Shield.
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