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Gryaznova, Anastasiya C
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Gryaznova, Anastasiya C
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- PublicationRestrictedNew Data on the Structure of the Megatransform System of the Doldrums (Central Atlantic)(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ;The geological and geophysical data acquired during cruise 45 of R/V Akademik Nikolaj Strakhov regarding the structure of the Doldrums megatransform system in the Central Atlantic are presented. Taking into account the data of the previous expeditions, the structure of this region is examined in detail. The bathymetric data confirm the complex morphology, consisting of five dextral transform faults, separated by four active intra-transform rift segments and indicates the variability of tectonic conditions in this region. The dredged rocks are represented by the entire spectrum from the mantle to the upper crustal varieties and, together with the detailed topographic data, make it possible to identify the origin of the key structures in the Doldrums megatransform system.121 4 - PublicationOpen AccessLarge-scale structure of the Doldrums multi-fault transform system (7-8ºN equatorial atlantic): preliminary results from the 45th expedition of the r/v a.N. Strakhov(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ; ; ;The Equatorial portion of the Mid Atlantic Ridge is displaced by a series of large offset oceanic transforms, also called “megatransforms”. These transform domains are characterized by a wide zone of deformation that may include different conjugated fault systems and intra-transform spreading centers (ITRs). Among these megatransforms, the Doldrums system (7-8ºN) is arguably the less studied, although it may be considered the most magmatically active. New geophysical data and rock samples were recently collected during the 45th expedition of the R/V Akademik Nikolaj Strakhov. Preliminary cruise results allow to reconstruct the large-scale structure and the tectonic evolution of this poorly-known feature of the Equatorial Atlantic. Swath bathymetry data, coupled with extensive dredging, were collected along the entire megatransform domain, covering an area of approximately 29,000 km2. The new data clearly indicate that the Doldrums is an extremely complex transform system that includes 4 active ITRs bounded by 5 fracture zones. Although the axial depth decreases toward the central part of the system, recent volcanism is significantly more abundant in the central ITRs when compared to that of the peripheral ITRs. Our preliminary interpretation is that a region of intense mantle melting is located in the central part of the Doldrums system as consequence of either a general transtensive regime or the occurrence of a more fertile mantle domain. Large regions of basement exposure characterize the transform valleys and the ridge-transform intersections. We speculate that different mechanisms may be responsible for the exposure of basement rocks. These include the uplift of slivers of oceanic lithosphere by tectonic tilting (median and transverse ridges formation), the denudation of deformed gabbro and peridotite by detachment faulting at inner corner highs, and the exposure of deep-seated rocks at the footwall of high-angle normal faults at the intersection of mid-ocean ridges with transform valleys.175 43 - PublicationRestrictedMultidisciplinary Investigation of the Transform Fault Zones Doldrums and Vema during Cruise 45 of the R/V “Akademik Nikolaj Strakhov”(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ;Herein we provide information on the integrated geological, geophysical, sedimentological, paleoceanographic, hydrophysical and biological investigations in the Central Atlantic during the cruise 45 of the R/V “Akademik Nikolaj Strakhov” in October-November 2019. The preliminary scientific results are discussed.124 4