Magmatic and tectonic segmentation of the intermediate-spreading Costa Rica Rift—a fine balance between magma supply rate, faulting and hydrothermal circulation

Robinson, A. H.; Zhang, L.; Hobbs, Richard; Peirce, C.; Tong, C. H.

doi:10.1093/gji/ggaa152

Cited by 6 publications

(17 citation statements)

References 119 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5e) demonstrates a comparable velocity range to that observed in the ~1800 m-deep borehole logs (~4.5-6.5 km s −1 ;Alt et al 1996), with only the lower velocity of volcanic extrusives absent from the model. At the CRR, the Vp model has a very close fit to the inversion model ofRobinson et al (2020) throughout the ~4 km sub-basement sampled by both models. In Layer 3, Vp also increases with distance from the CRR, consistently displaying a steeper velocity-depth profile and reaching a higher velocity at shallower depth relative to the top basement.…”

mentioning

confidence: 75%

“…The thinner (~5 km-thick) crust model, which is founded on the 4.5 km-thick crust indirectly inferred by Collins et al (1989), achieved a minimum model misfit of c 2 = 4.9. Comparatively, the more typical (~6 km-thick) crust model (as assumed in Wilson et al 2019;Robinson et al 2020) was able to achieve a slightly improved total model misfit of c 2 = 3.8, with a notable reduction in the misfit of the Moho reflection (PmP) phase picks (c 2 = 1.1, compared with c 2 = 3.3 in the thin-crust model - Table 1).…”

Section: Poisson's Ratiomentioning

confidence: 96%

“…Fig. 1) that connected two 3-D grid surveys; one located across the current CRR spreading centre (North Grid or NG - Robinson et al 2020) and the other on ~6.9 Myr old crust surrounding 504B (South Grid or SG -Gregory 2018), the latter providing direct lithological and downhole log constraint (e.g. Detrick et al 1994;Alt et al 1996;Carlson 2010).…”

Section: Geological and Tectonic Contextmentioning

confidence: 99%

“…Van Avendonk et al 1998;Audhkhasi & Singh 2019;Peirce et al 2019a,b;Wilson et al, 2019;Christeson et al 2020;Davy et al 2020), and three-dimensional tomographic grids (e.g. Toomey et al 1990;Gregory 2018;Robinson et al 2020;Simao et al 2020), that have become more detailed through the use of greater numbers of instrumentation deployed at smaller spatial intervals and able to sample at higher temporal rates. These improvements in instrumentation, jointly with increased computational power and more complex modelling methods, have enabled increasingly high-resolution imaging of oceanic crustal structure.…”

Section: Introductionmentioning

confidence: 99%

“…The black and grey lines correspond to the SAP profiles as labelled, with the inverted triangles, and associated numbers, representing OBSs deployed along SAP_B. The two dashed-grey boxes represent the footprints of two 3-D tomographic grids acquired (SG -Gregory 2018;NG -Robinson et al 2020). The red-coloured OBS are those whose data is presented inFigs 2 and 3,…”

mentioning

confidence: 99%

See 4 more Smart Citations

Evolution and properties of young oceanic crust: constraints from Poisson's ratio

Funnell

Robinson

Hobbs

et al. 2021

Geophysical Journal International

Self Cite

View full text Add to dashboard Cite

Summary The seismic velocity of the oceanic crust is a function of its physical properties that include its lithology, degree of alteration, and porosity. Variations in these properties are particularly significant in young crust, but also occur with age as it evolves through hydrothermal circulation and is progressively covered with sediment. While such variation may be investigated through P-wave velocity alone, joint analysis with S-wave velocity allows the determination of Poisson's ratio, which provides a more robust insight into the nature of change in these properties. Here we describe the independent modelling of P- and S-wave seismic datasets, acquired along an ∼330 km-long profile traversing new to ∼8 Myr-old oceanic crust formed at the intermediate-spreading Costa Rica Rift (CRR). Despite S-wave data coverage being almost four-times lower than that of the P-wave dataset, both velocity models demonstrate correlations in local variability and a long-wavelength increase in velocity with distance, and thus age, from the ridge axis of up to 0.8 and 0.6 km s−1, respectively. Using the Vp and Vs models to calculate Poisson's ratio (σ), it reveals a typical structure for young oceanic crust, with generally high values in the uppermost crust that decrease to a minimum of 0.24 by 1.0–1.5 km sub-basement, before increasing again throughout the lower crust. The observed upper crustal decrease in σ most likely results from sealing of fractures, which is supported by observations of a significant decrease in porosity with depth (from ∼15 to < 2 per cent) through the dyke sequence in Ocean Drilling Program borehole 504B. High Poisson's ratio (>0.31) is observed throughout the crust of the north flank of the CRR axis and, whilst this falls within the ‘serpentinite’ classification of lithological proxies, morphological evidence of pervasive surface magmatism and limited tectonism suggests, instead, that the cause is porosity in the form of pervasive fracturing and, thus, that this is the dominant control on seismic velocity in the newly formed CRR crust. South of the CRR, the values of Poisson's ratio are representative of more typical oceanic crust, and decrease with increasing distance from the spreading centre, most likely as a result of mineralisation and increased fracture infill. This is supported by borehole observations and modelled 3-D seismic anisotropy. Crustal segments formed during periods of particularly low half-spreading rate (<35 mm yr−1) demonstrate high Poisson's ratio relative to the background, indicating the likely retention of increased porosity and fracturing associated with the greater degrees of tectonism at the time of their formation. Across the south flank of the CRR, we find that the average Poisson's ratio in the upper 1 km of the crust decreases with age by ∼0.0084 Myr−1 prior to the thermal sealing of the crust, suggesting that, to at least ∼7 Myr, advective hydrothermal processes dominate early CRR-generated oceanic crustal evolution, consistent with heat flow measurements.

show abstract

mentioning

confidence: 75%