Abstract
Petrology & geochemistry of the El Negrillar volcanic field, northern Chile
Abstracts with programs - Geological Society of America, Vol.51(2)
Geological Society of America, Southcentral Section, 53rd annual meeting; Northcentral Section, 53rd annual meeting; Rocky Mountain Section, 71st annual meeting
03/2019
Abstract
The El Negrillar or Negros de Aras volcanic field comprises a group of Pleistocene cinder cones and lava flows in northern Chile that lie to the west of the main Central Volcanic Zone arc-front volcanoes ( nearly equal 30 km north of Socompa; nearly equal 25 km northwest of Cerro Pular). Samples were collected from at least 9 different flow units and analyzed for major and trace element using ICP methods. Most of the lava flows are andesites, with one basaltic andesite and several dacites. Petrographically, the samples are sparsely phyric, with < 10% of microphenocrysts (< 1 mm) of olivine + plagioclase in the basaltic andesite, and plagioclase + clinopyroxene in the andesites and dacites. Major element compositions (e.g. 2-5 wt% MgO and 1.5-2.8 wt% K2O) are similar to the main arc-front volcanism. In contrast, incompatible trace element data show several features that mark the El Negrillar flows as compositionally distinct from the main arc-front volcanism. The El Negrillar flows have higher Sr (> 600 ppm) and higher Sr/Y (> 40), higher LREE/HFSE enrichment (e.g. La/Nb > 3), higher LREE-MREE (e.g. La/Sm > 5.2) and MREE-HREE (e.g. Dy/Yb > 2.4) enrichments and less-pronounced Eu-anomalies (Eu/Eu* > 0.85) compared to the main arc. About 15-30 km to the north & northeast, there are several isolated monogenetic centers (Cerro Tujle and Tilocalar Norte/Sul) that share similar petrographic and compositional characteristics with the El Negrillar volcanic field. These volcanic centers lie in an unusual tectonic position on the trench-side of the main Central Volcanic Zone arc-front volcanoes, and their locations are controlled by faulting associated with compressive deformation to the southeast of the Salar de Atacama.
Details
- Title: Subtitle
- Petrology & geochemistry of the El Negrillar volcanic field, northern Chile
- Creators
- Stephen Drop - University of Iowa, Department of Earth and Environmental Sciences Iowa City, IA USA United StatesBrennan van AlderwereltDavid W PeateIngrid Ukstins
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.51(2)
- Conference
- Geological Society of America, Southcentral Section, 53rd annual meeting; Northcentral Section, 53rd annual meeting; Rocky Mountain Section, 71st annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, South-Central Section, 53rd annual meeting; Geological Society of America, North-Central Section, 53rd annual meeting; Geological Society of America, Rocky Mountain Section, 71st annual meeting
- Language
- English
- Date published
- 03/2019
- Academic Unit
- Earth and Environmental Sciences; Honors Program
- Record Identifier
- 9984240889402771
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