scholarly journals The Paleoproterozoic Kandalaksha-Kolvitsa Gabbro-Anorthosite Complex (Fennoscandian Shield): New U–Pb, Sm–Nd, and Nd–Sr (ID-TIMS) Isotope Data on the Age of Formation, Metamorphism, and Geochemical Features of Zircon (LA-ICP-MS)

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 254 ◽  
Author(s):  
Ekaterina N. Steshenko ◽  
Tamara B. Bayanova ◽  
Pavel A. Serov

The paper provides new U–Pb, Sm–Nd, and Nd–Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. Rare earth element (REE) contents in zircons from basic rock varieties of the Kandalaksha-Kolvitsa area were analyzed in situ using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Plots of REE distribution were constructed, confirming the magmatic origin of zircon. Temperatures of zircon crystallization were estimated using a Ti-in-zircon geochronometer. The U–Pb method with a 205Pb artificial tracer was first applied to date single zircon grains (2448 ± 5 Ma) from metagabbro of the Kolvitsa massif. The U–Pb analysis of zircon from anorthosites of the Kandalaksha massif dated the early stage of the granulite metamorphism at 2230 ± 10 Ma. The Sm–Nd isotope age was estimated on metamorphic minerals (apatite, garnet, sulfides) and whole rock at 1985 ± 17 Ma (granulite metamorphism) for the Kolvitsa massif and at 1887 ± 37 Ma (high-temperature metasomatic transformations) and 1692 ± 71 Ma (regional fluid reworking) for the Kandalaksha massif. The Sm–Nd model age of metagabbro was 3.3 Ga with a negative value of εNd = 4.6, which corresponds with either processes of crustal contamination or primary enriched mantle reservoir of primary magmas.

2020 ◽  
Author(s):  
Ekaterina Steshenko ◽  
Tamara Bayanova ◽  
Pavel Serov ◽  
Nadezhda Ekimova

<p>The paper provides new U-Pb, Sm-Nd and Nd-Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. REE contents in zircons from basic rock varieties of the Kandalaksha-Kolvitsa area have been defined in situ using LA-ICP-MS. Plots of REE distribution have been constructed, confirming the magmatic origin of zircon. Temperatures of zircon crystallization have been estimated, using a Ti-in-zircon geochronometer. For the first time, the U-Pb method with <sup>205</sup>Pb artificial tracer has been applied to date single zircon grains (2448±5 Ma) from metagabbro of the Kolvitsa massif. The U-Pb analysis of zircon from anorthosites of the Kandalaksha massif has dated the early stage of the granulite metamorphism at 2230±10 Ma. The Sm-Nd isotope age has been estimated on metamorphic minerals (apatite, garnet, sulfides) and the rock at 1985±17 Ma (granulite metamorphism) for the Kolvitsa massif, 1887±37 Ma (high-temperature metasomatic transformations) and 1692±71 Ma (regional fluid reworking) for the Kandalaksha massif. The Sm-Nd model age of metagabbro is 3.3 Ga with negative value εNd=4.6, which corresponds either with processes of crustal contamination, or with primary enriched mantle reservoir of primary magmas.</p><p>This research was funded by the Scientific Research Contract of GI KSC RAS No. 0226-2019-0053, grants of the Russian Foundation for Basic Research NoNo. 18-05-70082 «Arctic Resources», 18-35-00246 mol_a, and the Presidium RAS Program No. 8.</p><p> </p>


LITOSFERA ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 683-698
Author(s):  
E. S. Karaseva ◽  
A. Yu. Kissin ◽  
V. V. Murzin

Research subject. The results of studying the geology and mineralogy of the Poldnevskoye deposit of demantoid are presented. Material and methods. The factual material was collected during feld research. Demantoid samples were pro vided by mine owners. Rock and vein minerals were studied in hand specimens, polished specimens and thin sections; the chemical composition was determined by X-ray fluorescence spectroscopy, scanning electron microscopy, electron probe X-ray spectral microanalysis, inductively coupled plasma mass spectrometry with laser sampling (LA-ICP-MS).Results. The Korkodinsky ultrabasic massif containing the deposit experienced strong decompression and syndecompression mineral formation during the ascent. At an early stage, veins of clinopyroxenite formed in dunite, which also experienced decompression cracking. Then the rocks underwent antigoritization and the appearance of vein antigorite, which was replaced by veins of clinochrysotile (+ magnetite ± carbonate ± demantoid). This was followed by the formation of lizardite (+ magnetite ± carbonate ± demantoid), which also developed along the earlier vein serpentines. Demantoid is represented by rounded grains and rounded grain aggregates with the signs of growth under the conditions of allround extension. The predominant color is brownish-green, yellow-green, rarely green and dark green. Green and dark green demantoids contain Cr2O3 0.52–2.3 wt %. In the central part of some grains and demantoid aggregates, a brown color is observed, which binds to TiO2, the content of which reaches 1 wt %. The demantoids of the Poldnevskoye deposit bear typomorphic features of the Ural-type demantoids (inclusions of the “horse’s tail” type). The distribution of demantoid is nested. The length of the veins with demantoid is frst meters. Their pillar-like shape is assumed. Conclusion.Demantoids from nests in serpentinized massive or brecciform dunites are more intact; demantoid nests in strongly serpentinized rocks were tectonic crushed and contain little gemstone.


Author(s):  
Aton Patonah ◽  
Haryadi Permana ◽  
Ildrem Syafri

Gabbro, is a fossil remnant of oceanic crust in western part of Java, found at Bayah Geological Complex (BGC) and Ciletuh Melange Complex (CMC), Indonesia. It has been studied by using petrographic, X-Ray Fluorescence (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS) and mineralogical (microprobe) analyses. Mineral and geochemical composition of these rocks provide important clues to their origins since the rocks have been deformed and gone through auto metamorphism, beside they contain the economic mineral and or rare earth elements (REE). Gabbroic rocks in these two areas generally shows phaneritic to porphyritic texture, granular texture. These rocks in CMC are dominated by plagioclase (oligoclase to albite), hornblende, pyroxene, partly altered to tremolite, actinolite, chlorite, epidote, and sericite; meanwhile those of BGC dominantly consist of plagioclase, pyroxene, hornblende, some present of chlorite, actinolite, epidote and biotite as secondary minerals. In multi-element diagrams, gabbroic rocks in CMC show strong negative Sr and Zr, but positive Nb anomaly, while those of BGC show strong negative anomaly of Nb and Zr. In addition, based on rare earth elements (REE) diagrams, gabbroic rocks in CMC show depleted of light rare earth elements (LREE) with negative Eu anomaly, while gabbro’s in BGC show enrichment of LREE. These characteristics indicate that GBC’s and CMC’s gabbroic rocks came from different magma sources, one was formed by partial melting of depleted upper mantle reservoir while the other one was formed by partial melting of mantle wedge with active participation of subducted slab in an arc tectonic setting, suprasubduction zone which were formed at started Upper Cretaceous to Paleogene, and they had retrograde metamorphism to epidote amphibolite facies.


2019 ◽  
Author(s):  
Ingo Strenge ◽  
Carsten Engelhard

<p>The article demonstrates the importance of using a suitable approach to compensate for dead time relate count losses (a certain measurement artefact) whenever short, but potentially strong transient signals are to be analysed using inductively coupled plasma mass spectrometry (ICP-MS). Findings strongly support the theory that inadequate time resolution, and therefore insufficient compensation for these count losses, is one of the main reasons for size underestimation observed when analysing inorganic nanoparticles using ICP-MS, a topic still controversially discussed.</p>


Author(s):  
Zixiao Pan ◽  
Wei Wei ◽  
Fuhe Li

Abstract This paper introduces our effort in failure analysis of a 200 nm thick metal interconnection on a glass substrate and covered with a passivation layer. Structural damage in localized areas of the metal interconnections was observed with the aid of focused ion beam (FIB) cross-sectioning. Laser ablation inductively coupled plasma mass spectroscopy (LA ICP-MS) was then applied to the problematic areas on the interconnection for chemical survey. LA ICP-MS showed direct evidence of localized chemical contamination, which has likely led to corrosion (or over-etching) of the metal interconnection and the assembly failure. Due to the high detection sensitivity of LA ICP-MS and its compatibility with insulating material analysis, minimal sample preparation is required. As a result, the combination of FIB and LA ICP-MS enabled successful meso-scale failure analysis with fast turnaround and reasonable cost.


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