Trend Surface Modelling of Karlapat Bauxite Deposit, Eastern Ghat Group, Orissa, India     

Bijaya Ketana NAYAK  Santanu Kumar SAHU  Rama Krishna SAHOO 《Resource Geology》2002,52(3):239-248

Abstract: The Karlapat bauxite deposit occurs in the Eastern Ghat Group of rocks in Orissa and has developed in the khondalites. Mineralogical and physical observations on bore hole samples reflect the presence of a maximum of six weathered zones from top to bottom. These zones are termed as topsoil, siliceous laterite, ferruginous laterite, bauxite, lithomarge and altered khondalite. Four-dimensional trend surface models are developed for the data of 45 and 36 bore holes from north and south blocks, respectively, on Al₂O₃ and SiO₂ to delineate the zones of metallurgical grade bauxite (SiO₂5 % and Al₂O₃40 %). The results indicate about 15 m thickness of bauxite in the north block while it could be up to 20 m thick in the south block, leaving about 10 m of lat-erites at the top of each block. High grade bauxite (>47 % Al₂O₃) is also encountered at specific locations.  相似文献   

Multi-model ensemble schemes for predicting northeast monsoon rainfall over peninsular India     

NACHIKETA ACHARYA  S C KAR  MAKARAND A KULKARNI  U C MOHANTY  L N SAHOO 《Journal of Earth System Science》2011,120(5):795-805

The northeast (NE) monsoon season (October, November and December) is the major period of rainfall activity over south peninsular India. This study is mainly focused on the prediction of northeast monsoon rainfall using lead-1 products (forecasts for the season issued in beginning of September) of seven general circulation models (GCMs). An examination of the performances of these GCMs during hindcast runs (1982–2008) indicates that these models are not able to simulate the observed interannual variability of rainfall. Inaccurate response of the models to sea surface temperatures may be one of the probable reasons for the poor performance of these models to predict seasonal mean rainfall anomalies over the study domain. An attempt has been made to improve the accuracy of predicted rainfall using three different multi-model ensemble (MME) schemes, viz., simple arithmetic mean of models (EM), principal component regression (PCR) and singular value decomposition based multiple linear regressions (SVD). It is found out that among these three schemes, SVD based MME has more skill than other MME schemes as well as member models.  相似文献   

Heavy Mineral Placer Deposits of Ekakula Beach, Gahiramatha Coast, Orissa, India     

Bhaskar Chandra ACHARYA  Prasanta Kumar PANIGRAHY  Binod Bihari NAYAK  Rama Krishna SAHOO 《Resource Geology》1998,48(2):125-136

Abstract: Ilmenite, hematite, garnet, monazite, zircon, rutile, magnetite, sillimanite, pyroxene and amphibole from the beach sands of Ekakula, Gahiramatha coast, Orissa, India are reported here for the first time. Their total concentration varies from 26. 4 to 100%. Ilmenite, monazite and zircon are between 100 and 300 um in size and are well rounded in shape. Ilmenite-hematite intergrowth is common. Ilmenite has 50. 02–54. 73% TiO₂, 42. 42–46. 90% FeO (total Fe) and small amounts of Al, Mn, Mg, Ca, Ba, Si, V, Cr, and Zn. The bulk samples contain 10. 63–41. 42 % TiO₂, 6. 15–26. 07 % FeO, 5. 86–16. 75 % Fe₂O₃, 7. 41–61. 74 % SiO₂, 1. 39–12. 83% A1₂O₃, 0. 32–4. 97% CaO, 0. 53–4. 24% P₂O₅, 0. 17–3. 27% MgO, 0. 15–2. 97% Na₂O, 0. 07–2. 34% K₂O, and 0. 05–0. 71% V₂O₅ together with appreciable amounts of La, Ce, Pr, Nd, Sm, Eu, Y, U, Th, Zr, and trace amounts of Pb, Zn, Cu, Ni, Co, and Cr. Khondalite, charnockite, calc-silicate granulite, leptynite, migmatite, gneiss, basic granulite and pegmatite of the Eastern Ghats appear to be the major source for the above heavy mineral assemblages. The samples are amenable to gravity and magnetic methods of beneficiation.  相似文献   

Controls on large‐scale patterns of fluvial sandbody distribution in alluvial to coastal plain strata: Upper Cretaceous Blackhawk Formation,Wasatch Plateau,Central Utah,USA     

GARY J. HAMPSON  M. ROYHAN GANI  HIRANYA SAHOO  ANDREAS RITTERSBACHER  ANDREW RANSON  JOHN A. HOWELL  SIMON J. BUCKLEY  BRYAN BRACKEN 《Sedimentology》2012,59(7):2226-2258

Current models of alluvial to coastal plain stratigraphy are concept‐driven and focus on relative sea‐level as an allogenic control. These models are tested herein using data from a large (ca 100 km long and 300 m thick), continuous outcrop belt (Upper Cretaceous Blackhawk Formation, central Utah, USA). Many channelized fluvial sandbodies in the Blackhawk Formation have a multilateral and multistorey internal character, and they generally increase in size and abundance (from ca 10% to ca 30% of the strata) from base to top of the formation. These regional, low‐resolution trends exhibit much local variation, but are interpreted to reflect progressively decreasing tectonic subsidence in the upper Blackhawk Formation and overlying Castlegate Sandstone. The trend may also incorporate progressively more frequent channel avulsion during deposition of the lower Blackhawk Formation. Laterally extensive coal zones formed on the coastal plain during shallow‐marine transgressions, and define the high‐resolution stratigraphic framework of the lower Blackhawk Formation. Large (up to 25 m thick and 1 to 6 km wide), multistorey, multilateral, fluvial channel‐complex sandbodies that overlie composite erosion surfaces occur at distinct stratigraphic levels, and are interpreted as fluvial incised valley fills. Low amplitude (<30 m) relative sea‐level variations are interpreted as the dominant control on stratigraphic architecture in the lower Blackhawk Formation, which was deposited up to 50 km inland from the coeval shoreline. In contrast, the high‐resolution stratigraphy of the upper Blackhawk Formation is poorly defined, and channelized fluvial sandbodies are poorly organized. Vertical and laterally offset stacking of a small proportion (<10%) of sandbodies produced ‘clusters’ that are not confined by ‘master’ erosion surfaces. Avulsion is interpreted to dominate the stratigraphic architecture of the upper Blackhawk Formation. This data‐driven analysis indicates that alluvial to coastal plain stratigraphic architecture reflects a combination of various allogenic controls and autogenic behaviours. The relative sea‐level control emphasized in sequence stratigraphic models is only rarely dominant.  相似文献