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Long-term thermo-tectonic evolution of the Montes de Toledo area (Central Hercynian Belt, Spain): constraints from apatite fission-track analysis

Barbero González, Luis C. and Glasmacher, U. A. and Villaseca González, Carlos and López García, José Ángel and Martín Romera, Cristina (2005) Long-term thermo-tectonic evolution of the Montes de Toledo area (Central Hercynian Belt, Spain): constraints from apatite fission-track analysis. International journal of earth sciences, 94 . pp. 193-203. ISSN 1437-3254

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Abstract

Abstract In the Montes de Toledo area, located in the
axial part of the Central Hercynian zone, a long-term
thermo-tectonic evolution can be deduced from apatite
fission-track (AFT) data in conjunction with tight geological
constraints derived from the knowledge of regional
geology and other independent chronometers.
The area is composed of two different blocks separated
by the Toledo Shear Zone (TSZ). The northern block is
a granulite facies anatectic terrane. The southern block
is composed of greenschist facies Paleozoic sediments
intruded by a late Hercynian granitic pluton. A total of
13 samples have been recovered for AFT analysis. AFT
ages in both blocks cluster around 189–221 Ma, with
mean confined track lengths between 11.4 lm and
12.4 lm. Modeling of the AFT data indicates that the
thermal history is broadly similar in both blocks, which
constrains the main movement of the TSZ, as essentially
before the Upper Permian. AFT ages in the TSZ cluster
around 124–164 Ma, and the track lengths vary between
11.4 lm and 12.4 lm. These data reveal that the fault
must have been affected by a later thermal overprint as
AFT ages are significantly younger than those of the
footwall and hangingwall blocks. This differential thermal
resetting is likely related to the advection of localized
hydrothermal fluids that are responsible for the
widespread Pb–Zn mineralization along the TSZ. These
results give an example of resetting AFT data by
hydrothermal events. The long-term evolution suggests a
lack of important Alpine tectonism in the Montes de
Toledo block, in clear contrast to other nearby Hercynian
areas such as the Sierra de Guadarrama, where the
important effect of Alpine tectonism has almost totally
erased the previous thermal signal in the AFT system.

Item Type:Article
Uncontrolled Keywords:Spanish Central Hercynian Zone; Apatite fission-track dating; Resetting related to fluids; Mesozoic and Cenozoic thermal history
Subjects:Sciences > Geology > Petrology
Sciences > Geology > Geodynamics
ID Code:12305
Deposited On:28 Feb 2011 12:34
Last Modified:28 Feb 2011 12:34

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