Оползневая опасность на Шуфанском плато для линейных объектов инфраструктуры (Приморский край)

Active visco-elastic mudslide streams are widely developed along the edges of basaltic flow formations on the Shufan Plateau. Brief orographic, tectonic, and geologic assessment of the area is given. Landslides, revinement, denudation violate the normal transportation rhythm. The results of studying the process conditions and causes are discussed. It is established that the main cause of mudflows is traffic arteries tracing along the low-grade (12-15 degrees) slopes built by unconsolidated clays, with of the clays transformation into plastic state during long drizzles, common in the area, as the principal one. Working out options or engineering protection of railroads against the mudflows at the outskirts of Shufan Plateau has shown that each is highly problematic. Seismotectonic hazard of the regional Lower-Suyfun fault, coinciding with the Razdolnaya River valleyas well as modern vertical movements of the earth crust in the area discussed have to be taken into account while exploring the territory.

Paleomagnetism of the native copper mineralization, Keweenaw Peninsula, Michigan

The age and genesis of Michigan’s world-class native copper deposits are poorly constrained. The copper is hosted by basaltic flow tops and conglomeratic interbeds of the 1095 ± 2 Ma Keweenawan Portage Lake Formation. Progressive thermal demagnetization isolates stable hematite remanent magnetization components at 28 paleomagnetic sites. Paleomagnetic tilt tests show that magnetite in massive flow interiors is primary (1095 ± 2 Ma) and that hematite throughout the formation is syntectonic. The altered cupriferous deposits contain primary ∼1095 Ma and secondary ∼1053 Ma hematite in various proportions. The Caledonia Mine’s basaltic mineralization carries the ∼1053 Ma hematite dominantly whereas the Delaware Mine’s conglomeratic interbed mineralization carries the ∼1095 Ma hematite dominantly. The ∼1095 Ma hematite is attributed mostly to magnetite exsolution during flow extrusion and to weathering oxidation between extrusion events. An infusion of epigenetic hydrothermal fluids emplaced the native copper with additional hematite and polarity self-reversing titanohematite at 1053 ± 7 Ma. Importantly, paleomagnetic evidence supports a 1053 ± 7 Ma age also for the White Pine stratiform sedimentary copper mineralization, for the oxidation of the Oronto Group clastic rocks to red beds, and for the time limits of major tectonic uplift and deformation on the Keweenaw Peninsula.

Lower vendian ratno beds ore-bearing and its connection with rocks alteration (Chartoryisk fracture zone)

Newly formed secondary mineralization spreading features in Lower Vendian Ratno beds volcanic rock was determined. It is shown that the formation of impregnated native metals mineralization (copper, silver, nickel and chromium) associate with regional alteration lower basaltic flow of Ratno beds. The regional alteration is represented by palagonite, chlorite , zeolites, calcedony and analcime. It was found that the zones of increased fracturing and brecciation are accompanied by quartz, carbonates and sulphides with local distribution.

Comments on the eruption of basaltic magma at Tor Zawar, Balochistan, Pakistan on 27 January 2010, with a discussion of the geochemical and petrological constraints on its petrogenesis

An article by A. C. Kerr and coworkers published in 2010 in Mineralogical Magazine (74, 1027–1036), reviewed an event that was interpreted as the eruption of a basaltic flow on 27th January 2010, at Tor Zawar, Ziarat, Pakistan. The regional and local geology, volcanological aspects, petrography and major-element and trace-element analyses of two samples were presented. On the basis of these data it was proposed that this was a magmatic event and that the lava was derived from the mantle. On the basis of our extensive field work in the this area, and observations at the site of another similar incident that happened almost a year later (in January 2011) ∼300 m north of the first locality, we wish to clarify the geological context and propose an alternative origin.Our field observations suggest that both events were the result of localized surface melting at the base of metal electricity pylons, and their associated steel cable supports. The metal pylons and cable supports provided a path to earth for lightning discharges into the volcanic conglomerate of the Late Cretaceous Bibai Formation. We propose that this transmitted sufficient energy to melt the outcrop. We disagree with the proposal that the 'lava flows' at Tor Zawar were magmatic events and that the rocks formed are derived from the mantle. Alternatively, we propose that these 'lavas' were produced in a manner similar to fulgurites.

Lower Silurian subduction-related volcanic rocks in the Chaleurs Group, northern New Brunswick, CanadaGeological Survey of Canada, Contribution No. 2008-0166.Contribution to Natural Resources Canada’s Targeted Geoscience Initiative 3 (2005–2010).

Early Silurian volcanic and subvolcanic rocks are preserved in the lower part of the Chaleurs Group at two locations in northern New Brunswick. At Quinn Point, mafic to intermediate rocks are hosted by sedimentary rocks of the Weir Formation, and at Pointe Rochette, a bed of felsic tuff occurs near the base of the Weir. These rocks are interpreted as the first evidence in New Brunswick of magmatism associated with Late Ordovician – Early Silurian subduction of Tetagouche–Exploits back-arc oceanic crust. At Quinn Point, mafic rocks include a thick basaltic flow or sill and intermediate to mafic cobbles in overlying conglomerate beds. The in situ mafic rocks and the conglomerate clasts are chemically alike and display subduction-related affinities on tectonic discrimination diagrams. At Pointe Rochette, fine-grained felsic tuff contains elevated Th and U and depleted high-field-strength elements, consistent with a subduction-influenced setting, although rare-earth element (REE) abundances are low and the REE profile is relatively flat. A U–Pb (zircon) age of 429.2 ± 0.5 Ma was obtained from the tuff, consistent with the late Llandovery to early Wenlock age of the overlying La Vieille Formation and coinciding with the latter stages of development of the Brunswick subduction complex. Volcanic rocks were emplaced in the arc to arc-trench gap region, probably reflecting local step-back of the magmatic axis due to accretion of continental back-arc ribbons. The low volume of Early Silurian subduction-influenced rocks is probably related to the relatively narrow width of the back-arc basin and the young, “warm” character of back-arc crust.