Interaction of hydrothermal solutions and MORB: Junction of MAR and Green Cape transform fault

Summary The properties of the Mw = 6.7 earthquake that took place on 25 October 2018, 22:54:51 UTC, ∼50 km SW of the Zakynthos Island, Greece, are thoroughly examined. The main rupture occurred on a dextral strike-slip, low-angle, east-dipping fault at a depth of 12 km, as determined by teleseismic waveform modelling. Over 4000 aftershocks were manually analysed for a period of 158 days. The events were initially located with an optimal 1D velocity model and then relocated with the double-difference method to reveal details of their spatial distribution. The latter spreads in an area spanning 80 km NNW-SSE and ∼55 km WSW-ENE. Certain parts of the aftershock zone present strong spatial clustering, mainly to the north, close to Zakynthos Island, and at the southernmost edge of the sequence. Focal mechanisms were determined for 61 significant aftershocks using regional waveform modelling. The results revealed characteristics similar to the mainshock, with few aftershocks exhibiting strike-slip faulting at steeper dip angles, possibly related to splay faults on the accretionary prism. The slip vectors that correspond to the east-dipping planes are compatible with the long-term plate convergence and with the direction of coseismic displacement on the Zakynthos Island. Fault-plane solutions in the broader study area were inverted for the determination of the regional stress-field. The results revealed a nearly horizontal, SW-NE to E-W-trending S1 and a more variable S3 axis, favouring transpressional tectonics. Spatial clusters at the northern and southern ends of the aftershock zone coincide with the SW extension of sub-vertical along-dip faults of the segmented subducting slab. The mainshock occurred in an area where strike-slip tectonics, related to the Cephalonia Transform Fault and the NW Peloponnese region, gradually converts into reverse faulting at the western edge of the Hellenic subduction. Plausible scenarios for the 2018 Zakynthos earthquake sequence include a rupture on the subduction interface, provided the slab is tilted eastwards in that area, or the reactivation of an older east-dipping thrust as a low-angle strike-slip fault that contributes to strain partitioning.

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Spatiotemporal clustering of great earthquakes on a transform fault controlled by geometry

Nature Geoscience ◽

10.1038/s41561-021-00721-4 ◽

2021 ◽

Author(s):

Jamie D. Howarth ◽

Nicolas C. Barth ◽

Sean J. Fitzsimons ◽

Keith Richards-Dinger ◽

Kate J. Clark ◽

...

Keyword(s):

Transform Fault ◽

Great Earthquakes ◽

Spatiotemporal Clustering

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An experimental study of biotite in Na-, F-, and Li-rich pneumatolyto-hydrothermal solutions

Chinese Journal of Geochemistry ◽

10.1007/bf02840432 ◽

1988 ◽

Vol 7 (1) ◽

pp. 76-87

Author(s):

Yu Yunmei ◽

Wang Yurong

Keyword(s):

Experimental Study ◽

Hydrothermal Solutions

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Coiraite, (Pb,Sn2+)12.5As3Fe2+Sn4+5 S28: a franckeite-type new mineral species from Jujuy Province, NW Argentina

Mineralogical Magazine ◽

10.1180/minmag.2008.072.5.1083 ◽

2008 ◽

Vol 72 (5) ◽

pp. 1083-1101 ◽

Cited By ~ 3

Author(s):

W. H. Paar ◽

Y. Moëlo ◽

N. N. Mozgova ◽

N. I. Organova ◽

C. J. Stanley ◽

...

Keyword(s):

Low Temperature ◽

Microprobe Analysis ◽

Electron Microprobe Analysis ◽

Mineral Species ◽

New Mineral ◽

Hydrothermal Solutions ◽

X Ray ◽

New Mineral Species ◽

Primary Mineral ◽

The Ideal

AbstractCoiraite, ideally (Pb,Sn2+)12.5As3Fe2+Sn4+S28, occurs as an economically important tin ore in the large Ag-Sn-Zn polymetallic Pirquitas deposit, Jujuy Province, NW-Argentina. The new mineral species is the As derivative of franckeite and belongs to the cylindrite group of complex Pb sulphosalts with incommensurate composite-layered structures. It is a primary mineral, frequently found in colloform textures, and formed from hydrothermal solutions at low temperature. Associated minerals are franckeite, cylindrite, pyrite-marcasite, as well as minor amounts of hocartite, Ag-rich rhodostannite. arsenopyrite and galena. Laminae of coiraite consist of extremely thin bent platy crystals up to 50 urn long. Electron microprobe analysis (n = 31) gave an empirical formula Pb11.21As2.99Ag0.13Fe1.10Sn6.13S28.0 close to the ideal formula (Pb11.3Sn2+1.2)Σ=12.5As3Fe2+Sn4+S28. Coiraite has two monoclinic sub-cells, Q (pseudotetragonal) and H (pseudohexagonal). Q: a 5.84(1) Å, b 5.86(1) Å, c 17.32(1) Å, β 94.14(1)°, F 590.05(3) Å3, Z = 4, a:b:c = 0.997:1:2.955; H (orthogonal setting): a 6.28(1) Å, b 3.66(1) Å, c 17.33(1) Å, β 91.46(1)°, V398.01(6) Å3, Z = 2, a∶b∶c = 1.716∶1∶4.735. The strongest Debye-Scherrer camera X-ray powder-diffraction lines [d in Å, (I), (hkl)] are: 5.78, (20), (Q and H 003); 4.34, (40), (Q 004); 3.46, (30), (Q and H 005); 3.339, (20), (Q 104); 2.876, (100), (Q and H 006); 2.068, (60), (Q 220).

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Volcanic History and Tectonics of the North Langjökull Region, Central Iceland

Canadian Journal of Earth Sciences ◽

10.1139/e73-019 ◽

1973 ◽

Vol 10 (2) ◽

pp. 164-179 ◽

Cited By ~ 10

Author(s):

J. D. A. Piper

Keyword(s):

Late Pleistocene ◽

Volcanic Activity ◽

Active Zone ◽

Ice Sheet ◽

North Coast ◽

Crustal Growth ◽

Transform Fault ◽

Active Volcanism ◽

The North ◽

Lava Pile

The geology of the area around the northern part of the Langjökull ice sheet in central Iceland is outlined. This area includes the termination of the western neovolcanic zone, two silicic centers, and basaltic interglacial, intraglacial, and postglacial volcanoes. The lava succession becomes older to the northwest of the area where the zone of young volcanoes gives away to a pile of lavas of pre-Bruhnes epoch age which dip at low angles towards the active zone.This active zone undergoes a change in strike from NE–SW to north–south near latitude 64 °55′N and the volcanoes north of this are smaller in volume than those on the southern extension of the zone. The area of Bruhnes epoch activity dies out above latitude 65 °10′N but much of the area between here and the north coast of Iceland was a line of volcanic activity during the preceding Matuyama epoch.The northern part of the western active zone in Iceland became inactive in late Pleistocene times, and the southern part of the zone is an area of continuing crustal growth. The zone of active volcanism does not terminate against a transform fault and crustal growth is accommodated by deformation of the crustal plate. Lines of crustal growth which subsequently die out can be invoked to explain the anticline and syncline structures in the lava pile and the currently-active Snaefellsnes zone in western Iceland.

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