TY  - JOUR
A1  - Vasquez, Mónica
A1  - Altenberger, Uwe
A1  - Romer, Rolf L.
A1  - Sudo, Masafumi
A1  - Moreno-Murillo, Juan Manuel
T1  - Magmatic evolution of the Andean Eastern Cordillera of Colombia during the Cretaceous : Influence of previous tectonic processes
N2  - The Eastern Cordillera of the Colombian Andes represents an inverted Cretaceous basin where Cretaceous magmatism is characterized by rare mafic dykes and sills. We use Ar-40/Ar-39, Sr-Nd-Pb isotopes, as well as major and trace elements analyses of Cretaceous intrusions from both flanks of the Eastern Cordillera in combination with structural data to document the complex evolution of the basin. Magmatism, which is diachronous and geochemically diverse, seems to be related to mantle melting beneath the most subsiding segments of each sub-basin during enhanced extensional tectonics. The mafic intrusions display two different compositional series: an alkaline one with OIB-like pattern and a tholeiitic one with MORB-like features. This indicates at least two diverse mantle sources. Trace-element patterns suggest that the intrusions were emplaced in an extensional setting. Ar-40/Ar-39 dating on primary plagioclase and hornblende provides plateau ages between similar to 136 and similar to 74 Ma. The geochemical and temporal diversities show that the emplacement of the magmas was tectonically controlled, each sub-basin reflecting an individual subsidence event.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/08959811
U6  - https://doi.org/10.1016/j.jsames.2009.02.003
SN  - 0895-9811
ER  - 
TY  - JOUR
A1  - Wilke, Franziska Daniela Helena
A1  - O'Brien, Patrick J.
A1  - Altenberger, Uwe
A1  - Konrad-Schmolke, Matthias
A1  - Khan, M. Ahmed
T1  - Multi-stage reaction history in different eclogite types from the Pakistan Himalaya and implications for exhumation processes
N2  - Metabasites were sampled from rock series of the subducted margin of the Indian Plate, the so-called Higher Himalayan Crystalline, in the Upper Kaghan Valley, Pakistan. These vary from corona dolerites, cropping out around Saif- ul-Muluk in the south, to coesite-eclogite close to the suture zone against rocks of the Kohistan arc in the north. Bulk rock major- and trace-element chemistry reveals essentially a single protolith as the source for five different eclogite types, which differ in fabric, modal mineralogy as well as in mineral chemistry. The study of newly-collected samples reveals coesite (confirmed by in situ Raman spectroscopy) in both garnet and omphacite. All eclogites show growth of amphiboles during exhumation. Within some coesite-bearing eclogites the presence of glaucophane cores to barroisite is noted whereas in most samples porphyroblastic sodic-calcic amphiboles are rimmed by more aluminous calcic amphibole (pargasite, tschermakite, and edenite). Eclogite facies rutile is replaced by ilmenite which itself is commonly surrounded by titanite. In addition, some eclogite bodies show leucocratic segregations containing phengite, quartz, zoisite and/or kyanite. The important implication is that the complex exhumation path shows stages of initial cooling during decompression (formation of glaucophane) followed by reheating: a very similar situation to that reported for the coesite-bearing eclogite series of the Tso Morari massif, India, 450 km to the south-east.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00244937
U6  - https://doi.org/10.1016/j.lithos.2009.07.015
SN  - 0024-4937
ER  -