West Pit Research Articles

Economic evaluation of mineral deposit: A bottom-up approach

Proper economic evaluation of a mineral deposit is critical to effective investment decision-making in a mineral project. However, this often requires detailed mine production scheduling to produce a schedule that reflects the actual cash flow when the project comes on stream. Because of the dexterity required for this task many mine planners and explorationist attempt to use statistical formulas that approximate the mine scheduling and value of the project. The mathematical model developed for production scheduling often produces a constant production rate schedule over an approximate life span of the project. In this paper, we have attempted to apply a bottom-up approach that begins with geometrical modelling and equipment deployment pattern to define the number of equipment required for each sequence of operation based on available workfront in the development of each bench. Then, based on the number of equipment and the production rate at each sequence of operations, a production schedule is developed. This production schedule therefore will reflect annual cash flow since it is based on the sequence of operation. Application of this method on the west pit of Itakpe mine shows a considerable net present value and internal rate of return of the deposit compared with the evaluation made using statistical models. The NPV of the west pit was found to be USD621 million as against USD122.41 million using Nwosu’s formula and USD123.85 million Taylor’s formula. The above value of NPV using the proposed method shows the maximum expected NPV of the mineral project-based technical restrictions. An understanding of this value can guide the mineral property owner in decision-making.

Detail mineralogical study and geochronological framework of Bayan Obo (China) Nb mineralization recorded by in situ U-Pb dating of columbite

The Bayan Obo deposit is world-famous for its giant rare earth reserves, and also accompanied with 2.2 Mt Nb2O5 resources at an average grade of 0.13 %, renowned as the second largest Nb deposit globally. Previous studies have focused on the origin of carbonatite (igneous/sedimentary), and variation composition during evolution, as well as its super-enrichment of light rare earth elements (LREE), while the metallogenic mechanism of niobium is being overlooked despite the identification of plenty Nb-bearing minerals. In this study, we identify four types of columbite as major Nb-bearing minerals, instead of pyrochlore in the west pit of Bayan Obo. Detailed mineralogical study has revealed large primitive columbite (Clb1-I, 100–200 μm) is hosted in the coarse-grained Fe-dolomite carbonatite (FeO = 5.46–10.47 wt%), being an ideal target for future mineral beneficiation. Those columbites (Clb1-I) are featured by lowest Sr, Y, and ∑REE but enriched in iron in composition, revealing its magmatic origin. Sieve-textured columbite (Clb1-II, ∼100 μm) dispersed in the fluorination and chloritization dolomite carbonatite, with a U–Pb age of 1359 ± 31 Ma, contemporary with ages of the regional carbonatite magma intrusion and rift-related magmatism, indicating niobium being sourced from mantle-derived carbonatite. The occurrence of fluorite as inclusions in Clb1-I indicates the solubility of Nb was enhanced by fluxes, and the columbite saturation was easily achieved during the carbonatite magma evolution into ferroan carbonatite. Strong fenitization metasomatism further locally concentrated columbite either within the mineral assemblages of pyrite + phlogopite + allanite (Clb2) or in the mica-dominated fenite (Clb3), and crystallized at 346 ± 18 Ma and 284 ± 16 Ma, respectively. The latter metalogenetic epoch is accordant with late Permian granitic magmatism event (ca. 280 Ma) while the former age may attribute to its occurrences related to the early Paleozoic arc-continent collision. Differ from pristine columbite (Clb1-I and Clb1-II), the metamorphic columbite (Clb2 and Cl3, especially Clb3) are enriched in Ta (1803–4092 ppm), Y (560–2029 ppm) and ∑REE (720–6317 ppm) content, probably suggesting the highest degree of evolution. The similar metallogenesis framework between Nb and REE, combined with the coexistence of columbite and REE minerals assemblages, implies the spatial and temporal coupling of Nb and REE mineralization. This first innovative and systematic mineralogical and geochronological work directly constrains the nature of Mesoproterozoic mantle-derived carbonatite with fertile Fe and fluxes, and the Paleozoic and Permian fenitization metasomatism, are the major factors contribute to the metallogenic specialization of niobium in Bayan Obo.

Engineering Geology and Slope Stability of West Pit Coal Mine of PT. Tawabu Mineral Resource, East Kalimantan, Indonesia

The research area was located in the west pit of the open pit coal mine of PT. Tawabu Mineral Resource (TMR) which is located in Bengalon District, East Kutai Regency, East Kalimantan Province, Indonesia. The research was driven by several landslides that occurred in the research area, but the engineering geological conditions and stability of the remaining slopes have not been evaluated. The objectives of this study were to better understand the engineering geological conditions and stability of the research area. The engineering geological conditions (i.e., geomorphology, rock and soil, geological structure, and groundwater conditions) were evaluated by photogrametric analyses, field observations, and analyses of borehole logs and laboratory test results. The slope stability analyses were firstly carried out by conducting back stability analyses of failed slope on the northern lowwall slope segment. The shear strength parameters obtained from the back analyses were then used for forward stability analyses of the remaining 10 lowwall and highwall slopes. The slope stability analyses involved deterministic and probabilistic analyses, under static and dynamic using the limit equilibrium method (LEM). The results showed that the research area and the surrounding consisted of two geomorphological units, namely the alluvial plain and structural hills. Rocks in the study area consisted of claystone, sandstone, and coal with a general layer strike direction of N59°E – N63°E with a dip of 19°-26°. These rocks were grouped into two lithological units, namely the alternating of claystone and sandstone unit and alternating of sandstone and claystone unit. The geological structures were identified on the highwall, from west to east namely major sinistral shear fault with a relative direction of NNE-SSW, two minor sinistral shear faults with a relative direction of NE-SW, and a major dextral shear fault with a relative direction of NW-SE. These geological structures were interpreted as being formed by the folding process. The groundwater level was estimated at a level of -45 m to 20 m. The slope stability analyses showed that only the East HW-4 slope, which was located on the east highwall, was unstable. It is recommended to optimize the slope by either lowering the groundwater elevation by 4 m from the actual level or by reducing the angle the overall slope to 31°.

Trace precious metals in major sulfide minerals from the Federova Tundra platinum group element deposit in the Fedorova-Pana layered intrusion, central Kola Peninsula, Russia

ABSTRACTDrill-core samples from the basal Cu-Ni-platinum-group element mineralization of the Early Proterozoic Fedorova Tundra intrusion in the Fedorova-Pana layered intrusion, central Kola Peninsula, Russia, were studied in two separate projects in Canada and Russia. In Canada, trace precious metal analyses by laser ablation inductively coupled mass spectrometry of 323 base metal sulfide particles [pentlandite (101), pyrrhotite (98), chalcopyrite (25), and pyrite (99)] show that Pd is highly concentrated in pentlandite. Most of the analyses (71%) were done using two master composite samples of comminuted drill core representative of the West Pit and East Pit mineralization, FWMC and FEMC, respectively. Fewer analyses were made of three other comminuted drill core samples from the West Pit referred to as “lithology” samples: OLFW (olivine-bearing rocks), ANFW (leucocratic rocks), and GNFW (gabbronorite). In Russia, 120 polished sections sliced from drill core from the West and East Pits and from four other Fedorova Tundra intrusion deposits (Kievey, Northern Kamennik, Eastern Chuarvy, and Southern Kievey) were studied mineralogically. Platinum group mineral characterization and trace Pd electron probe microanalyses of pentlandite were done using polished sections from all six locations (n = 95). The trace electron probe microanalysis data for Pd in pentlandite from the West (n = 35) and East (n = 19) Pit samples, though at much higher detection levels, are considered to be comparable to the laser ablation inductively coupled mass spectrometry data. The Eastern Chuarvy samples show particularly high Pd concentrations averaging 0.49 wt.% Pd (n = 11) and as high as 1.64 wt.% Pd. The combined data from these studies guides our estimate that pentlandite accounts for 30 to 50% of the Pd in these ores and that Rh solid solution in sulfides may account for >98% of the total Rh.

Metals and metalloid in gold mine pit lakes and fish intake risk assessment, Burkina Faso.

This study aimed to determine the levels of metals and metalloid (arsenic) in pit lakes from a gold mining site and in their fishes and assess their potential health effect on the local human population, in order to evaluate whether pit lakes can be safely used for aquaculture. Water quality data were collected from two pit lakes, namely West Pit 1 (WP1) and West Pit 2 (WP2), and the Nakambé River (NR) in Burkina Faso. Fish consumption rates in different villages were assessed through a survey. Commonly available fish were sampled from the pit lakes and the NR. Fish from the pit lakes contained higher amounts of metals and metalloid than fish from the river (WP1 ~ WP2 < NR). Of the four species of fish considered, Oreochromis niloticus and Hydrocynus forskahlii had the highest metals and metalloid content and Bagrus bajad and Clarias anguillaris had the lowest. The results indicated that the consumption of the whole fish results in higher metals and metalloid intake than consumption of the fleshy part only. Due to the low fish intake of 5.34 ± 2.60g/day/adult deduced from the nutritional survey, exposure to metals and metalloid was below referential doses. The highest arsenic intake comes from eating entire O. niloticus (0.058mg/day/adult) from WP1. Eating O. niloticus and C. anguillaris exposes people to an arsenic intake of 0.01mg/day/adult. The arsenic contents of H. forskahlii and B. bajad were below the method detection limit.

Structure of Lō‘ihi Seamount, Hawai‘i and Lava Flow Morphology From High-Resolution Mapping

High-resolution bathymetric data were collected using AUV Sentry at the summit and at two hydrothermal vent fields on the deep south rift of L¯o‘ihi Seamount. The summit map records a nested series of caldera and pit crater collapse events, uplift of one resurgent block, and eruptions that formed at least five low lava shields that shaped the summit. The earliest and largest caldera, formed ~5900 years ago, bounds almost the entire summit plateau. The resurgent block was uplifted slightly more than 100 m and has a tilted surface with a dip of about 6.5° towards the SE. The resurgent block was then modified by collapse of a pit crater centered in the block that formed West Pit. The shallowest point on L¯o‘ihi’s summit is 986 m deep and is located on the northwest edge of the resurgent block. Several collapse events culminated in formation of East Pit, and the final collapse formed Pele’s Pit in 1996. The nine mapped collapse and resurgent structures indicate the presence of a shallow crustal magma chamber, ranging from depths of ~1 km to perhaps 2.5 km below the summit, and demonstrate that shallow sub-caldera magma reservoirs exist during the late pre-shield stage. On the deep south rift zone are young medium- to high-flux lava flows that likely erupted in 1996 and drained the shallow crustal magma chamber to trigger the collapse that formed Pele’s Pit. These low hummocky and channelized flows had molten cores and now host the FeMO hydrothermal field. The Shinkai Deep hydrothermal site is located among steep-sided hummocky flows that formed during low-flux eruptions. The Shinkai Ridge is most likely a coherent landslide block that originated on the east flank of L¯o‘ihi.

KEMAMPUAN TANAMAN EKOR KUCING (Typha latifolia) DAN PURUN TIKUS (Eleocharis dulcis) DALAM PENURUNAN KONSENTRASI Fe DAN Mn DARI AIR LIMBAH PIT BARAT PT PAMAPERSADA NUSANTARA DISTRIK KCMB KABUPATEN BANJAR

Research on the Ability Test Ekor kucing Plants (Typha latifolia) and Purun tikus (Eleocharis dulcis) in Fe and Mn concentrations decrease from the West Pit Wastewater PT Pamapersada District KCMB Kabupaten Banjar. This research held in April 2013 to August 2013. The purpose of this study was to determine the ability of plants Ekor kucing and plants Purun tikus in lowering the concentration of Fe and Mn from waste coal mine and phytoremediation mechanisms that occur. This research uses experimental and survey methods. Results showed that plants Ekor kucing and Purun tikus are hiperakumulator plants to Fe and Mn in which the plant is able to absorb Fe respectively by 284% and 92%. For Mn, respectively 207% and 1277%. Phytoremediation mechanisms with Ekor kucing for Fe is fitostabilization and Purun tikus is fitoextraction, while the Mn is fitoextraction.

Genetic Stratigraphy of Uranium Host Facies, Tordilla Sandstone Member, Upper Jackson Group, Panna Maria, Texas: ABSTRACT

Uranium mineralization in the Panna Maria, Texas, area occurs in the Tordilla Sandstone Member of the Eocene upper Jackson Whitsett Formation on the reduced side of a linear alteration front that extends more than 3 mi (5 km) along strike. Two open-pit mines at Panna Maria expose parts of a strike-oriented sand belt associated with a barrier island-tidal inlet system. The east pit exposes (1) a tidal inlet-embayment entrance, overlain by (2) tidal-channel, and (3) tidal-flat facies. The inlet facies, the uranium host, is dominantly fine to very fine sand End_Page 759------------------------------ with multidirectional trough and planar cross-bedding, Ophiomorpha sp., rounded mud clasts, and mud blocks. The tidal channel cuts through tidal-flat deposits, is approximately 40 m wide and 11 m thick, and contains gently dipping accretion beds of fine to very fine sand, including small-scale cross-stratification, and upwardly decreasing sand bed thickness. The lithology and sedimentary structures of facies 3 strongly resemble classic tidal-flat deposits of the Wadden Sea. The west pit exposes a regressive sequence of (1) tidal-inlet fill, (2) a poorly represented upper shoreface-beach-barrier flat facies, overlain by (3) bay-lagoon deposits. The inlet facies of fine to very fine sand includes large-scale, low-angle planar cross-beds, Ophiomorpha sp., bipolar, planar cross-beds, and has a scoured base. Some zones are highly burrowed. Facies 2 consists of trough and planar cross-bedded fine to very fine sand, with low-angle parallel bedding, root traces, and woody fragments near a hummocky upper surface. Facies 3 includes an ashy, burrowed lignite overlain by a massive, burrowed clayey siltstone containing plant debris. Facies 1 and 2, as well as the base of the lignite bed, are uranium bearing. End_of_Article - Last_Page 760------------

March 1965 eruption of Kilauea volcano and the formation of Makaopuhi Lava Lake

From March 5 to 15, 1965, Kilauea volcano erupted over 15 million cubic meters of tholeiitic basalt along the upper east rift zone between Makaopuhi and Kalalua craters. A pond of basalt 83 meters deep was left within the west pit of Makaopuhi crater. The eruption was preceded by inflation of the Kilauea summit and was accompanied by collapse of the summit. Observed horizontal, vertical, and tilt changes accompanying inflation of Kilauea before and after the eruption cannot fit any simple model for inflation of a single magma chamber. Data for the collapse are even farther from agreement with the draining of a single chamber. Seismic activity was exceptionally low in the months preceding the eruption and during the eruption. Amplitude of harmonic tremor correlates with the rate of fountaining during the eruption. Temperatures of the erupted lavas have been estimated at 1190°–1200°C by extrapolation of thermocouple data obtained in Makaopuhi lava lake. A comparison with temperatures of other Kilauea eruptions measured by optical pyrometer indicates that the best optical pyrometry yields temperatures 35°–75° lower than the true temperature of eruption. The erupted lavas were olivine-poor tholeiitic basalts. Lavas erupted at successively later times down rift are shown to be differentiated from the lavas erupted at Makaopuhi crater by removal of olivine, clinopyroxene, and minor plagioclase during transport in the rift zone.

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