The study describes an analysis of the impact of plantation forestry on the taxonomic diversity of plants in south-central Chile. In this biodiversity hotspot, plantations of non-native species like Pinus radiata D. D...The study describes an analysis of the impact of plantation forestry on the taxonomic diversity of plants in south-central Chile. In this biodiversity hotspot, plantations of non-native species like Pinus radiata D. Don, Eucalyptus globules Labill. and Populus nigra L. have largely replaced native deciduous and sclerophyllous forests. The study compares taxonomic diversity of commercial plantations and native forests using taxonomic distinctness and diversity and the Simpson diversity index. Most of these indexes attest a considerably reduced taxonomic diversity to plantations. However, taxonomic distinctness values for P. radiata plantations seem to contradict other indexes at first glance. It is shown that the higher values of taxonomic distinctness of P. radiata plantations come from taxonomic dominance. Taxonomic dominance describes the fact that P. radiate—a member of the infradivison of Gymnospermae-bears only little taxonomic resemblance to other plants, which are Angiospermae. Thus, it strongly dominates the taxonomic distinctness index and the high taxonomic resemblance of other plant within its plots is neglected. Indexes are developed that identify such dominant species and adjust for taxonomic dominance in taxonomic diversity analyses. After this adjustment, all indexes provide a coherent image on taxonomic diversity. Plantation forestry produces a considerable decline of taxonomic diversity. Taxonomic diversity analysis provides valuable insights in biodiversity impacts and complements standard analyses.展开更多
Many gold placers located in the Coastal Range of south-central Chile have been exploited commercially during the past decades;nevertheless and until now, there are not any exploration studies of these placers and the...Many gold placers located in the Coastal Range of south-central Chile have been exploited commercially during the past decades;nevertheless and until now, there are not any exploration studies of these placers and their basement. In order to provide an overview of exploratory potential, the stream sediments that are part of several gold placers in the northwest area of the BioBío region are analyzed, which have been registered on the basis of empirical evidence from artisanal mining activities. The overview consists of two goals: 1) determine the presence of auriferous occurrences (stream sediments and basement) and 2) identify potentially favorable areas to find gold placer deposits. Through optical microscopy this study characterized the metallic and non-metallic mineralogy of the basement, along with geochemical analyses of stream sediments and surrounding rocks of the placer deposits. The geochemical results show two sectors with high precious metal contents in sediments (up to 24 ppm of Au and 8 ppm of Ag) and two rocky outcrops with Au (757 and 41 ppb). Additionally, there are depressions in the study area that have received large amounts of sediments (reaching up to 170 m-thick), which are favorable places for the accumulation of auriferous sediments from nearby valleys due to the tectonic and structural conditions where they are located. Then, these results show an exploratory potential for gold placers and can be useful to delineate future exploration strategies in the Coastal Range of south-central Chile.展开更多
South-central Chile has some potential mineral resources including radioactive and rare earth elements (REE) minerals. This study reports some basic characteristics of the mineralogy of a radioactive-rare earth elemen...South-central Chile has some potential mineral resources including radioactive and rare earth elements (REE) minerals. This study reports some basic characteristics of the mineralogy of a radioactive-rare earth elements occurrence, related to a pegmatitic outcrop “Vertientes Pegmatite” hosted on Paleozoic granitic rocks of the South Coastal Batholith and discusses potential areas for REE deposits, particularly beach placers along the coastline of the BioBío region. In this pegmatite, X-ray diffraction analysis shows uranium-bearing minerals such as coffinite and metaschoepite, along with microcline, anorthoclase, albite, quartz and illite. Through optical microscopy and electron probe micro-analyzer (EPMA), rare earth minerals (monazite and xenotime) and radioactive minerals (thorite and thorium silicate ± uranium) were identified. Additionally, granitic rocks of the South Coastal Batholith around this pegmatite show rare earth minerals (monazite and allanite).展开更多
文摘The study describes an analysis of the impact of plantation forestry on the taxonomic diversity of plants in south-central Chile. In this biodiversity hotspot, plantations of non-native species like Pinus radiata D. Don, Eucalyptus globules Labill. and Populus nigra L. have largely replaced native deciduous and sclerophyllous forests. The study compares taxonomic diversity of commercial plantations and native forests using taxonomic distinctness and diversity and the Simpson diversity index. Most of these indexes attest a considerably reduced taxonomic diversity to plantations. However, taxonomic distinctness values for P. radiata plantations seem to contradict other indexes at first glance. It is shown that the higher values of taxonomic distinctness of P. radiata plantations come from taxonomic dominance. Taxonomic dominance describes the fact that P. radiate—a member of the infradivison of Gymnospermae-bears only little taxonomic resemblance to other plants, which are Angiospermae. Thus, it strongly dominates the taxonomic distinctness index and the high taxonomic resemblance of other plant within its plots is neglected. Indexes are developed that identify such dominant species and adjust for taxonomic dominance in taxonomic diversity analyses. After this adjustment, all indexes provide a coherent image on taxonomic diversity. Plantation forestry produces a considerable decline of taxonomic diversity. Taxonomic diversity analysis provides valuable insights in biodiversity impacts and complements standard analyses.
文摘Many gold placers located in the Coastal Range of south-central Chile have been exploited commercially during the past decades;nevertheless and until now, there are not any exploration studies of these placers and their basement. In order to provide an overview of exploratory potential, the stream sediments that are part of several gold placers in the northwest area of the BioBío region are analyzed, which have been registered on the basis of empirical evidence from artisanal mining activities. The overview consists of two goals: 1) determine the presence of auriferous occurrences (stream sediments and basement) and 2) identify potentially favorable areas to find gold placer deposits. Through optical microscopy this study characterized the metallic and non-metallic mineralogy of the basement, along with geochemical analyses of stream sediments and surrounding rocks of the placer deposits. The geochemical results show two sectors with high precious metal contents in sediments (up to 24 ppm of Au and 8 ppm of Ag) and two rocky outcrops with Au (757 and 41 ppb). Additionally, there are depressions in the study area that have received large amounts of sediments (reaching up to 170 m-thick), which are favorable places for the accumulation of auriferous sediments from nearby valleys due to the tectonic and structural conditions where they are located. Then, these results show an exploratory potential for gold placers and can be useful to delineate future exploration strategies in the Coastal Range of south-central Chile.
文摘South-central Chile has some potential mineral resources including radioactive and rare earth elements (REE) minerals. This study reports some basic characteristics of the mineralogy of a radioactive-rare earth elements occurrence, related to a pegmatitic outcrop “Vertientes Pegmatite” hosted on Paleozoic granitic rocks of the South Coastal Batholith and discusses potential areas for REE deposits, particularly beach placers along the coastline of the BioBío region. In this pegmatite, X-ray diffraction analysis shows uranium-bearing minerals such as coffinite and metaschoepite, along with microcline, anorthoclase, albite, quartz and illite. Through optical microscopy and electron probe micro-analyzer (EPMA), rare earth minerals (monazite and xenotime) and radioactive minerals (thorite and thorium silicate ± uranium) were identified. Additionally, granitic rocks of the South Coastal Batholith around this pegmatite show rare earth minerals (monazite and allanite).
