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Cooper D.J.,Colorado State University | Wolf E.C.,Colorado State University | Wolf E.C.,University of California at Davis | Colson C.,Tetra Tech Inc. | And 3 more authors.
Arctic, Antarctic, and Alpine Research

An ecological analysis of wetlands in the high mountain jalca above 3700 m elevation in the Andes near Cajamarca, Peru, indicated that most wetlands are groundwater-supported peat-accumulating fens. The floristic composition of fen communities was controlled largely by groundwater chemistry, which was highly variable and influenced by watershed bedrock composition. Watersheds with highly mineralized rock discharged water as acidic as pH 3.7, which was high in CaSO4, while watersheds with limestone, marble, and skarn produced groundwater as basic as pH 8.2 and high in CaHCO3. Of the 125 plots sampled in 36 wetland complexes, >50 of plots had at least 3 m of peat, and 21 plots had peat thicker than 7 m. Most soil horizons analyzed had 18 to 35 organic carbon, indicating high C storage. A total of 102 vascular plants, 69 bryophytes, and 10 lichens were identified. Study plots were classified using TWINSPAN into 20 plant communities, which were grouped into four broad categories by dominant life form: (1) cushion plant communities, (2) sedge- and rush-dominated communities, (3) bryophyte and lichen communities, and (4) tussock grass communities. Direct gradient analysis using canonical correspondence analysis indicated that Axis 1 was largely a water chemistry gradient, while Axis 2 was a complex hydrology and peat thickness gradient. Bryophytes and lichens were more strongly separated in the ordination space than vascular plants and were better indicators of specific environmental characteristics. © 2010 Regents of the University of Colorado. Source

Garcia S.,Minera Yanacocha SRL | Ramon C.,Minera Yanacocha SRL | Esplin A.,Minera Yanacocha SRL | Gebhardt J.E.,SALt Inc | And 3 more authors.
Minerals and Metallurgical Processing

The Minera Yanacocha operation presents various operating challenges, due to the complex structure of several heaps interconnected with ponds and gold recovery plants. A comprehensive process model has been developed in order to better understand the effects of certain operating parameters on issues such as water usage and inventory. An integral component of the water/mass balance of the process is a model of each heap that describes the flow and chemical behavior based on the individual characteristics of the heap. A computational fluid dynamic (CFD) software framework is used to model the individual heaps. The structure, calibration and validation of the model are described. Several examples demonstrating application of the process heap model are presented for the La Quinua heap. The effects of loss of solution flow to the heap (i.e., pump failure), increased cyanide levels in applied solutions and higher copper head grades on the process operation and balance are investigated with model simulations and compared to the baseline operating conditions. An example of estimating gold production and inventory based on projected heap loading plans is provided. Copyright 2010, Society for Mining, Metallurgy, and Exploration, Inc. Source

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