Tracing Crustal Evolution in the Southern Central Andes from Late Precambrian to Permian with Geochemical and Nd and Pb Isotope Data

2000 ◽  
Vol 108 (5) ◽  
pp. 515-535 ◽  
Author(s):  
B. Bock ◽  
H. Bahlburg ◽  
G. Wörner ◽  
U. Zimmermann
Keyword(s):  
Central Andes ◽  
Crustal Evolution ◽  
Pb Isotope ◽  
Late Precambrian ◽  
Isotope Data ◽  
Southern Central

RETROARC BASIN REORGANIZATION AND DIACHRONOUS ARIDIFICATION DURING PALEOGENE UPLIFT OF THE SOUTHERN CENTRAL ANDES

2016 ◽  
Author(s):  
Julie C. Fosdick ◽  
◽  
Barbara Carrapa ◽  
Barbara Carrapa ◽  
Ellen J. Reat ◽  
...  
Keyword(s):  
Central Andes ◽  
Southern Central

A COUPLED LACUSTRINE AND ALLUVIAL FAN RECORD FOR THE HOLOCENE OF THE ARID SOUTHERN CENTRAL ANDES

2017 ◽  
Author(s):  
José Luis Antinao ◽  
◽  
Rachel Tiner ◽  
Rachel Tiner ◽  
Rachel Tiner ◽  
...  
Keyword(s):  
Central Andes ◽  
Alluvial Fan ◽  
The Holocene ◽  
Southern Central

scholarly journals Petrogenesis of a late-stage calc-alkaline granite in a giant S-type batholith: geochronology and Sr–Nd–Pb isotopes from the Nomatsaus granite (Donkerhoek batholith), Namibia

2021 ◽  
Author(s):  
S. Aspiotis ◽  
S. Jung ◽  
F. Hauff ◽  
R. L. Romer
Keyword(s):  
Partial Melting ◽  
Mineral Assemblage ◽  
Central Zone ◽  
Calc Alkaline ◽  
Pb Isotope ◽  
Alkaline Granite ◽  
Ti Oxides ◽  
Eu Anomaly ◽  
Environment Characteristic ◽  
Southern Central

AbstractThe late-tectonic 511.4 ± 0.6 Ma-old Nomatsaus intrusion (Donkerhoek batholith, Damara orogen, Namibia) consists of moderately peraluminous, magnesian, calc-alkalic to calcic granites similar to I-type granites worldwide. Major and trace-element variations and LREE and HREE concentrations in evolved rocks imply that the fractionated mineral assemblage includes biotite, Fe–Ti oxides, zircon, plagioclase and monazite. Increasing K2O abundance with increasing SiO2 suggests accumulation of K-feldspar; compatible with a small positive Eu anomaly in the most evolved rocks. In comparison with experimental data, the Nomatsaus granite was likely generated from meta-igneous sources of possibly dacitic composition that melted under water-undersaturated conditions (X H2O: 0.25–0.50) and at temperatures between 800 and 850 °C, compatible with the zircon and monazite saturation temperatures of 812 and 852 °C, respectively. The Nomatsaus granite has moderately radiogenic initial 87Sr/86Sr ratios (0.7067–0.7082), relatively radiogenic initial εNd values (− 2.9 to − 4.8) and moderately evolved Pb isotope ratios. Although initial Sr and Nd isotopic compositions of the granite do not vary with SiO2 or MgO contents, fSm/Nd and initial εNd values are negatively correlated indicating limited assimilation of crustal components during monazite-dominated fractional crystallization. The preferred petrogenetic model for the generation of the Nomatsaus granite involves a continent–continent collisional setting with stacking of crustal slices that in combination with high radioactive heat production rates heated the thickened crust, leading to the medium-P/high-T environment characteristic of the southern Central Zone of the Damara orogen. Such a setting promoted partial melting of metasedimentary sources during the initial stages of crustal heating, followed by the partial melting of meta-igneous rocks at mid-crustal levels at higher P–T conditions and relatively late in the orogenic evolution.

Geochemistry and isotope systematics of small- to medium-volume Neogene–Quaternary ignimbrites in the southern central Andes: evidence for derivation from andesitic magma sources

2001 ◽  
Vol 171 (3-4) ◽  
pp. 213-237 ◽  
Author(s):  
Wolfgang Siebel ◽  
Wolfgang B.W. Schnurr ◽  
Knut Hahne ◽  
Bernhard Kraemer ◽  
Robert B. Trumbull ◽  
...  
Keyword(s):  
Central Andes ◽  
Andesitic Magma ◽  
Magma Sources ◽  
Southern Central ◽  
Isotope Systematics

scholarly journals Early last glacial maximum in the southern Central Andes reveals northward shift of the westerlies at ~39 ka

2011 ◽  
Vol 7 (1) ◽  
pp. 41-46 ◽  
Author(s):  
R. Zech ◽  
J. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
Last Glacial Maximum ◽  
Central Andes ◽  
Glacial Maximum ◽  
Atmospheric Co2 ◽  
Dissolved Carbon ◽  
Last Glacial ◽  
Exposure Dating ◽  
Latitudinal Position ◽  
Southern Central ◽  
Southern Westerlies

Abstract. The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka), resulting in reduced deep ocean ventilation, accumulation of old dissolved carbon, and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

scholarly journals Timing and extent of late pleistocene glaciation in the arid Central Andes of Argentina and Chile (22°-41°S)

2017 ◽  
Vol 43 (2) ◽  
pp. 697 ◽  
Author(s):  
J. Zech ◽  
C. Terrizzano ◽  
E. García-Morabito ◽  
H. Veit ◽  
R. Zech
Keyword(s):  
Southern Oscillation ◽  
Co2 Concentration ◽  
Late Glacial ◽  
Central Andes ◽  
The North ◽  
Eastern Equatorial Pacific ◽  
Southern Central ◽  
Study Sites ◽  
Increasing Temperature ◽  
Exposure Ages

The arid Central Andes are a key site to study changes in intensity and movement of the three main atmospheric circulation systems over South America: the South American Summer Monsoon (SASM), the Westerlies and the El Niño Southern Oscillation (ENSO). In this semi-arid to arid region glaciers are particularly sensitive to precipitation changes and thus the timing of past glaciation is strongly linked to changes in moisture supply. Surface exposure ages from study sites between 41° and 22°S suggest that glaciers advanced: i) prior to the global Last Glacial Maximum (gLGM) at ~40 ka in the mid (26°- 30°S) and southern Central Andes (35°-41°S), ii) in phase with the gLGM in the northern and southern Central Andes and iii) during the late glacial in the northern Central Andes. Deglaciation started synchronous with the global rise in atmospheric CO2 concentration and increasing temperature starting at ~18 ka. The pre-gLGM glacial advances likely document enhanced precipitation related to the Southern Westerlies, which shifted further to the North at that time than previosuly assumed. During the gLGM glacial advances were favored by decreased temperatures in combination with increased humidity due to a southward shifted Intertropical Convergence Zone (ITCZ) and SASM. During the late-glacial a substantial increase in moisture can be explained by enhanced upper tropospheric easterlies as response to an intensified SASM and sustained La Niña-like conditions over the eastern equatorial Pacific that lead to glacial advances in the northern Central Andes and the lake level highstand Tauca (18-14 ka) on the Altiplano. In the southernmost Central Andes at 39º-41°S, further north at 31°S and in the northernmost Central Andes at 22°S glacial remnants even point to precipitation driven glaciations older than ~115 ka and 260 ka.

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