Ore Piles Research Articles

Vegetation-Derived Insights on the Mobilization and Potential:Transport of Radionuclides from the Nopal I Natural Analog Site, Mexico

AbstractThe Nopal I uranium (U) deposit, Peñia Blanca, Mexico is a source term and contaminant transport natural analog to the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. In an attempt to characterize the mobilization and potential transport of adionuclides in the unsaturated zone at the Nopal I deposit, vegetation growing on ore piles was analyzed for238U,235U, and232Th decay-series isotopes. Specimens ofPhacelia robustagrowing on highgrade piles of U ore were collected and analyzed by alpha autoradiography, and by alpha and gamma spectrometry. Activities for U, thorium (Th), and radium (Ra) isotopes (Bq/kg dried plant) were 300, 1000, and 7000 for238U,230Th, and226Ra, respectively. The226Ra activities in these specimens are among the highest ever measured for plants; furthermore, the plant-to-soil226Ra concentration ratio is higher than expected. These results demonstrate the large mobility and bio-availability of Ra in the Nopal I environment, and support previous indications of recent loss of226Ra from the ore body. Comparison between the activities of238U and232Th decay-chain Th isotopes in the plants and in the ore substrate indicate that relative mobilization into pore solutions of228Th >230Th >232Th, in a ratio of about 50 – 25:4:1, respectively. The similarity of the plant's234U/238U activity ratio (˜1.2) to that of a caliche deposit that formed adjacent to the Nopal ore body around 54 ka suggests the234U/238U activity ratio of U released from the ore is approximately 1.2. The U and236Ra isotope activities of the plants and ore substrate, and solubility considerations, are used to assess a source term model of the potential Yucca Mountain repository. These results suggest the use of a natural analog source term model in performance assessments may be non-conservative.

積み込み作業計画のための鉱石堆積物モデル

This paper proposes a computer model of ore pile for scooping task planning. Ore pile has irregular shape which changes during scooping operation. For the effective task planning in the autonomous scooping system, it would be required to predict the change of pile shape due to gravity flow of rock, initiated by scooping.The proposed model is composed of column elements which simplify the structure and shorten the processing time. The working place is tessellated into sections which are bases of the columns. The hight of a column represents the hight of ore at the center of corresponding section. However, the size of each section and the unit hight of column are not coincident with particle size of ore. The model represents the shape, mass and falling behavior of the pile under the assumption which simplifies the falling motion of ore particles.The small scale experiment of scooping in laboratory shows that the predicted shape and the measured shape after each scooping are consistent with each other, and the predicted and measured scooped volume at each scooping are agree very well. The proposed model has sufficient accuracy and performance for the scooping task planning.

The ore textures of the Neves-Corvo volcanogenic massive sulphides and their implications for ore beneficiation

AbstractThe Neves-Corvo mine opened officially in December 1988 and it is already the biggest producer of copper in the Iberian Pyrite Belt (IPB). Tin production started in 1990. The ore deposits of the IPB are related to felsic submarine volcanism which developed during the lower Tournaisian to the middle Visean. At the end of the first phase of Hercynian deformation in the middle Westphalian, the ore deposits were affected by low-pressure metamorphism producing schistosity and prehenite-pumpellyite greenschist facies assemblages in the volcanogenic sediments of the IPB.The unique nature of the mineralogy of the Neves-Corvo deposit compared with other IPB deposits is mainly a result of the introduction of later Cu-rich hydrothermal solutions to the primitive ore pile and the presence of tin mineralisation. The cupriferous ores are rich in tetrahedrite-tennantite, stannite, kesterite, stannoidite and mawsonite.Cassiterite occurs in Neves-Corvo: (a) as thin layers of euhedral crystals in cupriferous ores, partially replaced by chalcopyrite; (b) in the schistosity of a banded black shale chalcopyrite hanging wall formation; (c) as metre-sized lenses of massive cassiterite overlying the cupriferous ores.The ore textures at Neves-Corvo are complex, due to intergrowths of fine colloform pyrite with the base metal minerals. Because of the low grade of metamorphism, colloform, geopetal and soft-sediment diagenetic features are preserved in the ‘complex ores’. These ‘complex ores’ have contents of 0.5% Cu, 1% Pb and 5.5% Zn. In copper-rich ores (7.9% Cu and 1.4% Zn), replacement of the primary ore by chalcopyrite has obliterated most of these textures and produced fine chalcopyrite-tetrahedrite-pyrite intergrowths. The textures clearly indicate the genesis of these ores but they impose a practical problem in recovery of the metals. There is no clear correlation between these textures and the ore classification used at the mine, but an understanding of the textures is vital since the ‘complex ores’ require fine grinding to achieve liberation and the fine grinding adversely affects the froth flotation processing of the ore.The implications of the complex sulphide textures for ore beneficiation have been studied using reflected light microscopy, with determination of modal analyses and grain-size distributions of free particles and middlings from concentrates and tailings.The outcome of a one-year intensive study is that the ore microscopy laboratory at the mine now produces daily information about the textures of the feed ores so that metallurgical engineers can optimise the performance of the ore dressing plant.

A Flora of the chrome and manganese ore piles at Canton, in the Port of Baltimore, Maryland and at Newport News, Virginia, with descriptions

A Flora of the chrome and manganese ore piles at Canton, in the Port of Baltimore, Maryland and at Newport News, Virginia, with descriptions

Stabilization of an Ore Pile by Drainage

Instability of track supporting one end of ore bridge in steel plant was caused by excess porewater pressure in layer of silt; successful permanent system of vacuum wellpoints was installed after preliminary field tests demonstrated feasibility of draining silt in this manner.