Magmatic Activity and Dynamics of Melt Supply of Volcanic Centers of Ultraslow Spreading Ridges: Hints From Local Earthquake Tomography at the Knipovich Ridge

Along ultraslow spreading ridges melt is distributed unequally, but melt focusing guides melt away from amagmatic segments toward volcanic centers. An interplay of tectonism and magmatism is thought to control melt ascent, but the detailed process of melt extraction is not yet understood. We present a detailed image of the seismic velocity structure of the Logachev volcanic center and adjacent region along the Knipovich Ridge. With travel times of P- and S-waves of 3,959 earthquakes we performed a local earthquake tomography. We simultaneously inverted for source locations, velocity structure and the Vp/Vs-ratio. An extensive low velocity anomaly coincident with high Vp/Vs-ratios >1.9 lies underneath the volcanic center at depths of 10 km below sea level in an aseismic area. More shallow, tightly clustered earthquake swarms connect the anomaly to a shallow anomaly with high Vp/Vs-ratio beneath the basaltic seafloor. We consider the deep low-velocity anomaly to represent an area of partial melt from which melts ascent vertically to the surface and northwards into the adjacent segment. By comparing tomographic studies of the Logachev and Southwest Indian Ridge Segment-8 volcano we conclude that volcanic centers of ultraslow spreading ridges host spatially confined, circular partial melt areas below 10 km depth, in contrast to the shallow extended melt lenses along fast spreading ridges. Lateral feeding over distances of 35 km is possible at orthogonal spreading segments, but limited at the obliquely spreading Knipovich Ridge. Key Points - Active volcanic centers at ultraslow spreading ridges host deeper and more confined partial melt areas than faster spreading ridges - Earthquake swarms delineate melt ascent paths from the partial melt area to the surface - Lateral feeding at shallow depths into subordinate segments is prevented by ridge obliquit

Caracterização de dez áreas com café conilon arborizado na Zona da Mata de Rondônia.

A presente pesquisa faz parte de um projeto maior de manejo da lavoura cafeeira arborizada e objetivou identificar as principais espécies utilizadas na arborização de áreas com cafeeiro Robusta nos município de Rolim de Moura e Nova Brasilândia do Oeste. A pesquisa foi desenvolvida em dez propriedades, cinco por município, e constou da aplicação de um questionário sócio-econômico, no qual foram levantadas a área total de cada propriedade, área com café Robusta, área com a(s) espécie(s) arborizadora, número de plantas, produtividade e idade do cafeeiro. Em Rolim de Moura a área total das propriedades avaliadas com cafeeiro Robusta arborizado é de 7,9 ha, a produtividade média varia de 10 a 100 sacas/ha, a idade do cafeeiro varia de 5 a 15 anos. No município de Nova Brasilândia a área total com café nas propriedades analisadas é de 15, 58ha, produtividade variando de 9 a 85 sacas/ha, a idade do cafeeiro varia de 5 a 21 anos