The accepted practice for the estimation of thin (2D) vein deposits recommends the use of the grade x thickness service variable (i.e., the accumulation). Grade estimates are obtained indirectly by the estimated accumulation/estimated thickness ratio. This practice stems from the varying support (thickness) problem and the resulting non-additive nature of the grade variable. We compare the actual performance of the direct grade estimation approach used by some practitioners to that of the indirect approach using accumulation. Our simulated and real data indicate that the direct approach is more accurate for point grade estimation where the grade-thickness correlation coefficient is positive (and vice-versa). Moreover, the relative gain of the direct method increases with the (positive) correlation coefficient. This finding contradicts common thinking that the indirect approach should be the preferred method where grade-thickness correlation is strongly positive. Also, for a given positive grade-thickness correlation, the relative gain of the direct method increases with the coefficient of variation of the grade and thickness. 

In their paper, Marcotte and Boucher (2001) cast some new light on the old problem of 2D estimation of vein-type deposits with thickness and grade of intercepts. Using a theoretical approach, some extensive simulation experiments and the Walker Lake data, they show that the direct approach (interpolation of grade at points on a regular grid) gives better estimates of the true grade at those points than the indirect approach (interpolation of grade x thickness or accumulation and interpolation of thickness) when there is some positive correlation between grade and thickness and that this better performance increases with the correlation of grade and thickness as well as the variability of both variables. We would like to bring some reservations to that conclusion by showing that even if direct point grade estimates are better than indirect ones, it is not necessarily true for block estimates and in particular for the estimated grade of the whole orebody itself. <...>

Оценка минеральных ресурсов структурно-сложных и прерывающейся минерализации с применением нелинейной геостатистики: на примере изучения мезотермального золотого оруденения Северной Канады

An estimation of resources of structurally complex gold lodes and stockworks represents a challenging task for geoscientists due to the complex geometry of the lodes and discontinuous grade. In the present case study, the resource of a gold stockwork has been estimated by uniform conditioning after the lode has been subdivided into geostatistically defined domains using the indicator probability model.

Позднепермское-раннетриасовое завершение аккреции южных Алтаид: значение для геодинамической эволюции, фанерозойского роста континента и металлогении Центральной Азии

The Altaids is one of the largest accretionary orogenic collages in the world with the highest rate of Phanerozoic continental growth and significant metallogenic importance. It is widely accepted that subduction-related orogenesis of the Altaids started in the late Precambrian and gradually migrated southward (present coordinates). However, it is uncertain when and how the building of the Altaids was finally completed.

In the article the features of the formation and metallogeny of the geological structures of Great Altai (Rudny Altai, Kalba-Narym, Western Kalba and Jarma-Saur) which are included into the system of the Central Asian mobile belt are considered. The characteristic of the main types of rare metal minefields of the Kalba-Narymsky belt genetically connected with the Perm granitoid magmatism of the post-conflict orogenny stage of activization is given. The rhythmical and pulsation model of pegmatitovy ore formation in the conditions of the half-closed magmatic system, reflecting the phasic development of mineral complexes from graphic and oligoclase-microcline (barren) to microcline-albite and albite-spodumene ore (Ta, Nb, Be, Li, Sn, etc.) is developed. On the basis of the revealed criteria of ore formation recommendations about the direction of the further researches are made. 

The Alpine-Balkan-Carpathian-Dinaride (ABCD) belt is one of the world’s oldest mining areas and played a major role in the history of European civilizations, from well before the peak of the Greek and Roman civilizations up untilthe present day. Today, it is Europe’s premier Cu-Au (-Pb-Zn-Ag) province, especially for gold-rich deposits associated with calc-alkaline magmatism, which have become a focus of renewed exploration interest after the political change in the eastern part of CentralEurope. The Alpine–Balkan–Carpathian–Dinaride metallogenic and geodynamic province is part of the AlpineHimalayan orogenic system which extends from western Europe through Iran and the Himalayas to China and Malaysia.

The Asian continent formed during the past 800 m.y. during late Neoproterozoic through Jurassic closure of the Tethyan ocean basins, followed by late Mesozoic circum-Pacific and Cenozoic Himalayan orogenies. The oldest gold deposits in Asia reflect accretionary events along the margins of the Siberia, Kazakhstan, North China, Tarim–Karakum, South China, and Indochina Precambrian blocks while they were isolated within the Paleotethys and surrounding Panthalassa Oceans. Orogenic gold deposits are associated with large-scale, terrane-bounding fault systems and broad areas of deformation that existed along many of the active margins of the Precambrian blocks. Deposits typically formed during regional transpressional to transtensional events immediately after to as much as 100 m.y. subsequent to the onset of accretion or collision. Major orogenic gold provinces associated with this growth of the Asian continental mass include:

Урановые месторождения в проницаемых водонасыщенных средах отрабатываются экономически эффективным способом подземного выщелачивания скважинными системами (СПВ). При оценке прогнозных ресурсов на поисково-оценочной стадии геологоразве-дочных работ необходимо учитывать, что промышленная ценность объектов, предназначенных для отработки СПВ, определяется не столько наличием урановой минерализации, сколько возможностью извлечения урана способом подземного выщелачивания, что устанавливается лабораторными и натурными геотехнологическими исследованиями.