Base-metal-rich metamorphosed black shales associated with Proterozoic ophiolites in the Kainuu schist belt,Finland: a genetic link with the Outokumpu rock assemblage

Metamorphosed black shale is an essential component of the Early Proterozoic Outokumpu rock assemblage, together with serpentinite, calc-silicate rock and quartz rock. This rock assemblage, hosting the major Cu-Co-Zn deposits of Outokumpu and considered ophiolitic in origin, has also been encountered to the northwest in the Kainuu schist belt. The rift basin encompassing the two areas was intruded by ophiolite complexes 1.96–1.97 billion years ago. Remnants of ultramafites are met as serpentinite and talc-carbonate rock lenses bounded by faults along the western margin of the Kainuu schist belt. The black schist formations range in thickness from tens of metres to 400 m. Metal-rich layers occur close to the serpentinite bodies. The most extensive formations of metal-rich black schist (300 Mt, 0.26% Ni, 0.14% Cu, 0.53% Zn) have been encountered at Talvivaara. The lithological, mineralogical and geochemical results indicate a genetic link between the Jormua, Talvivaara, Alanen and Pappilanmäki prospects in the Kainuu schist belt and the Outokumpu rock assemblage.     

Comparing the theoretical versions of the Beaufort scale, the T-Scale and the Fujita scale

2005 is the bicentenary of the Beaufort Scale and its wind-speed codes: the marine version in 1805 and the land version later. In the 1920s when anemometers had come into general use, the Beaufort Scale was quantified by a formula based on experiment. In the early 1970s two tornado wind-speed scales were proposed: (1) an International T-Scale based on the Beaufort Scale; and (2) Fujita's damage scale developed for North America. The International Beaufort Scale and the T-Scale share a common root in having an integral theoretical relationship with an established scientific basis, whereas Fujita's Scale introduces criteria that make its intensities non-integral with Beaufort. Forces on the T-Scale, where T stands for Tornado force, span the range 0 to 10 which is highly useful world wide. The shorter range of Fujita's Scale (0 to 5) is acceptable for American use but less convenient elsewhere. To illustrate the simplicity of the decimal T-Scale, mean hurricane wind speed of Beaufort 12 is T2 on the T-Scale but F1.121 on the F-Scale; while a tornado wind speed of T9 (= B26) becomes F4.761. However, the three wind scales can be uni-fied by either making F-Scale numbers exactly half the magnitude of T-Scale numbers [i.e. F′half = T / 2 = (B / 4) − 4] or by doubling the numbers of this revised version to give integral equivalence with the T-Scale. The result is a decimal formula F′double = T = (B / 2) − 4 named the TF-Scale where TF stands for Tornado Force. This harmonious 10-digit scale has all the criteria needed for world-wide practical effectiveness.