Furnes et al. (1) reported that a sheeted-dike complex they identified within the ~3.8billion-year-old Isua supracrustal belt (ISB) in Greenland provides the oldest evidence of oceanic crustal accretion by spreading. However, they did not alert readers that the ISB contains supracrustal rocks and mafic dikes of different ages (2, 3). They also failed to demonstrate that the proposed components ...

Over summer 2017, I continued my research on dikes emplaced during the waning stages of the Neoproterozoic-Ordovician Ross Orogen, a continental arc along the present day location of the Transantarctic Mountains in Antarctica. The dikes intrude calc-alkaline plutons constituting the main intrusive phase as well as metasedimentary rocks formed during early stages of orogenesis. These dikes compr...

available online at http://meteoritics.org 1675 © The Meteoritical Society, 2006. Printed in USA. Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary James W. HEAD* and John F. MUSTARD Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA *Corresponding aut...

in this study, the development of structural elements and the relationship between these elements and dikes emplacements investigated by the field surveys and analysis of satellite images of the east dasht-e bayaz fault zone. in this area nnw-sse (t2) and nw-se trending dikes are which follow the fractures of the region. we measured geometric characters of dikes (such as thickness, attitude, di...

[1] ODP/IODP Hole 1256D penetrates an in situ section of ocean crust formed at the East Pacific Rise, through lavas and sheeted dikes and ∼100 m into plutonic rocks. We use mineralogy, oxygen isotopes, and fluid inclusions to understand hydrothermal processes. The lavas are slightly altered at low temperatures (<150°C) to phyllosilicates and iron oxyhydroxides, with a stepwise increase in grade...

[1] The uppermost 2 km of oceanic crust created near the southern end of the Juan de Fuca Ridge ( 60 mm/yr, full spreading rate) is exposed in a ‘‘tectonic window’’ created along the north wall of the Blanco Transform Fault. A total of 27 submersible dives transect this escarpment over a distance of >30 km, corresponding to 1 m.y. of spreading history. In this exposure, weakly deformed basaltic...