The Upper Cretaceous Carmacks Group (70.4 ± 2.4 Ma) comprises gently dipping basaltic and andesitic lava flows overlying volcaniclastic deposits of the Intermontane Belt in the Whitehorse Trough. The sampling area is in southern Yukon and northern British Columbia; it lies west of the Tintina – Northern Rocky Mountain Trench fault and Teslin Suture Zone and east of the Denali – Shakwak fault. Volcanic sections were sampled in three regions spread over 300 km, providing the first paleomagnetic data from pre-Tertiary volcanic rocks in the northern Canadian Cordillera. Alternating-field and thermal demagnetization revealed stable magnetization for 18 of the 27 sites collected. The overall mean direction (D = 166.7°, I = −71.4°, k = 53, α95 = 4.8°, N = 18 sites) is pre-folding and is most probably primary (latest Cretaceous). This gives a paleopole at 109.4°E, 82.1°N, K = 21, A95 = 7.8°. A critical evaluation of North American cratonic data yields a reference paleopole for the latest Cretaceous at 185.8°E, 77...
SP monitoring of a sequence of water-acid-water injections over a span of three weeks in the Soultz geothermal reservoir shows a decrease of the surface electric potential during the acid stimulation. This requires a negative electrokinetic coupling coefficient, which is predicted by the theory for fluids with very low pH. Post-acid injections also yielded negative signals that are likely caused by electrochemical processes during the increase in ionic content of the injected water. These results have some importance when considering using acid stimulations for geothermal reservoirs in a production phase.
The profile of deep magnetotelluric sounding (MT) from Duc Trong - Tuy Phong has been carried out in Lam Dong and Binh Thuan provinces. The length of the Duc Trong - Tuy Phong profile is about 80 km with 15 stations and the distance between the stations measures about 5 km. Two-dimensional MT inversion was used to find a resistivity model that fits the data. The 2D resistivity model allows determining position and development formation of the Nha Trang - Tanh Linh fault. This is the deep fault, which is showed by the boundaries of remarkable change of resistivity. In the near surface of the Earth (from ground to the depth of 6 km), the angle of inclination of this fault is about 60o; in the next part, the direction of the Nha Trang - Tanh Linh faut is vertical. Geoelectrical section of the Nha Trang - Tanh Linh profile shows that the resistivity of mid-crust is higher than that of lower-crust and of upper-crust.
In 2013 the 12 stations of deep magnetotelluric sounding (MT) by Geo-instrument (made in France) on the profile about 25 km of long in the Quan Son - Quan Hoa districts of province Thanh Hoa has been carried out. The data was processed and 2D modeled by Geotools software. The obtained 2D resistivity cross-section until 30 km of depth represents structural features of earth crust here: High resistivity in the upper part of section until 10 -15 km of depth, indicates the consolidated rocks; low resistivity is distributed in lower part of section may be reflects the rock containing water relating to tectonic - geodynamic conditions, geothermal regime of earth's crust. Two low resistivity zones in center of profile with vertical development lightly indicate the Songma and the Sopcop - Quanson faults respectively, their positions are coincided with the distributions of these faults on the geological map.ReferencesCagnia L., 1953: Basic theory of magnetotelluric method of geophysical prospecting, Geophysics, 18, 605-635. Geotools Corporation, 1997: Geotools MT User’s guide. Ingham M., 2005: High resolution electrical imaging of faults zones, Phys. Earth Planet. Inter., 150, 93-105. Jones A., 1992: Electrical conductivity of the continental lower crust Continental lower Crust, edited by D. M, Fountain, R. J. Arculus and R. W. Kay. Lê Huy Minh, Đinh Văn Toàn, Võ Thanh Sơn, Nguyễn Chiến Thắng, Nguyễn Bá Duẩn, Nguyễn Hà Thành, Lê Trường Thanh, Guy Marquis, 2011: Kết quả xử lý bước đầu số liệu đo sâu từ tellua tuyến Hòa Bình – Thái Nguyên và tuyến Thanh Hóa - Hà Tây. Tạp chí các Khoa học về Trái Đất, 33(1), 18-28. Pham V. N., Boyer D., Nguyen Van Giang et Nguyen Thi Kim Thoa, 1995: Propriétés électriques et structure profonde de la zone de faille du Fleuve Rouge au Nord Vietnam d’après les résultats de sondage magnéto-tellurique, C. R. Acad. Sci. Paris, 320, série IIa, 181-187. Quomarudin M., 1994: Propriétés électriques et structures de la croûte en France, (Programmes Ecors, GPF) d’après les résultats de sondage magnéto-tellurique, Thèse, Université Paris 7. Smith J. T. & Booker J. R., 1991: The rapid relaxation inverse for two and three dimensional magnetotelluric data, J. Geophys. Res., 96, NO. B3, 3905-3922. Touret J. L. R. et Marquis G., 1994: Fluides profondes et conductivité électrique de la croûte continentale inférieure, C. R. Acad. Sci. Paris, 318, Série II, 1469-1482. Đoàn Văn Tuyến, Đinh Văn Toàn, 2011: Đặc điểm cấu trúc độ dẫn điện và mối quan hệ với dị thường địa nhiệt ở đới đứt gãy Sông Hồng. Tạp chí Các Khoa học về Trái Đất, 33(2), 10-17. Đoàn Văn Tuyến, Đinh Văn Toàn và Nguyễn Trọng Yêm, 2001: Đặc điểm cấu trúc địa động lực đới đứt gãy Sông Hồng trên cơ sở tài liệu từ telua. Tạp chí Địa chất, A267, 21-28. Vozoff K., 1972: The magnetotelluric method in the exploration of sedimentary basin. Geophysics, 37, No 1, 98-141.
Cette note présente un profil de sismique réflexion écoute longue, couplé à des sondages magnétotelluriques, qui recoupe l'ensemble des structures cadomiennes du Nord du Massif armoricain jusqu'au domaine de Bretagne centrale. Ce profil a été implanté à terre en continuité approximative du profil marin Swat10. La croûte supérieure apparaît peu réflective et ponctuellement marquée par des réflecteurs pentés. Ces réflecteurs, qui peuvent être corrélés avec des accidents connus en surface, représenteraient des décrochevauchements. La croûte inférieure est caractérisée par des réflecteurs horizontaux ou à faible pendage et la base de cette croûte litée semble correspondre au Moho. La géométrie des accidents de la croûte supérieure donne une image de prisme chevauchant à vergence sud-est, dont la semelle pourrait être le toit de la croûte inférieure litée. A new deep seismic profile has investigated the Upper Proterozoic terrains assembled during the Cadomian orogeny in the Northern Armorican Massif. This 60 km land profile prolongs the marine Swat 10 profile of the ECORS-BIRPS programme. Although the upper crust is poorly reflective on the stack section, several NW dipping reflectors have been observed and modelled from single shot records. They can be correlated with outcropping strike-slip and overthusting major contacts. The reflectivity of the lower crust, below 5 s, varies from one domain to another but it is relatively high and characterized by subhorizontal reflectors. The whole upper crustal Cadomian structures are interpreted as a SE verging overthusting prism the sole of which could be the top of the reflective lower crust.
Field estimation of the soil water flux has direct application for water resource management. Standard methods like tensiometry or time domain reflectometry are often difficult to use because of subsurface heterogeneity, whereas noninvasive tools such as electrical resistance tomography, nuclear magnetic resonance, or ground penetrating radar are limited to the estimation of the water content. We present an electrical method that provides water flux estimates: streaming potential (SP) monitoring. This cost‐effective tool may help to estimate the nature of the flow process (infiltration or evaporation) in the vadose zone. We discuss interpretation strategies in terms of numerical modeling of both hydraulic and electric processes in the vadose zone and propose an inversion scheme that allows the soil hydraulic parameters to be estimated from in situ infiltration experiments.
'%3e%3cpath id='a' fill='%23FF0' d='M0 0v6h4' transform='rotate(18)'/%3e%3cuse xlink:href='%23a' transform='scale(-1 1)'/%3e%3c/g%3e%3cg id='c' transform='rotate(72)'%3e%3cuse xlink:href='%23b'/%3e%3cuse xlink:href='%23b' transform='rotate(72)'/%3e%3c/g%3e%3cuse xlink:href='%23c' transform='scale(-1 1)'/%3e%3c/svg%3e)
