scholarly journals Petrology, Trace Element and Sr, Nd, Hf Isotope Geochemistry of the North Lanzo Peridotite Massif (Western Alps, Italy)

2012 ◽  
Vol 53 (11) ◽  
pp. 2259-2306 ◽  
Author(s):  
Luisa Guarnieri ◽  
Eizo Nakamura ◽  
Giovanni B. Piccardo ◽  
Chie Sakaguchi ◽  
Nobumichi Shimizu ◽  
...  
2015 ◽  
Vol 79 (4) ◽  
pp. 857-876 ◽  
Author(s):  
Kristoffer Szilas ◽  
J. Elis Hoffmann ◽  
Christina Hansmeier ◽  
Julie A. Hollis ◽  
Carsten Münker ◽  
...  

AbstractFragmented supracrustal rocks are typical components of Archaean high-grade gneiss terranes, such as those in the North Atlantic Craton. Here we present the first major, trace element and Nd-Hf isotope data for amphibolites collected in the yet poorly studied southern inner Ameralik fjord region of southern West Greenland. In addition, new U-Pb zircon ages were obtained from the surrounding TTG gneisses.Based on their trace-element patterns, two different groups of amphibolites can be distinguished. Following screening for post-magmatic alteration and outlying ε values, a reduced sample set defines a147Sm/143Nd regression age of 3038 Ma ±310 Ma (MSWD = 9.2) and a176Lu/176Hf regression age of 2867 ±160 Ma (MSWD = 5.5). Initial εNd2970Mavalues of the least-altered amphibolites range from 0.0 to +5.7 and initial εHf2970Ma range from +0.7 to +10.4, indicating significant isotopic heterogeneity of their mantle sources with involvement of depleted domains as well as crustal sources.Surprisingly, the amphibolites which are apparently most evolved and incompatible element-rich have the most depleted Hf-isotope compositions. This apparent paradox may be explained by the sampling of a local mantle source region with ancient previous melt depletion, which was re-enriched by a fluid component during subduction zone volcanism or alternatively by preferential melting of an ancient pyroxenite component in the mantle source of the enriched rocks.


Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 135
Author(s):  
Aurélie Labeur ◽  
Nicolas E. Beaudoin ◽  
Olivier Lacombe ◽  
Laurent Emmanuel ◽  
Lorenzo Petracchini ◽  
...  

Unravelling the burial-deformation history of sedimentary rocks is prerequisite information to understand the regional tectonic, sedimentary, thermal, and fluid-flow evolution of foreland basins. We use a combination of microstructural analysis, stylolites paleopiezometry, and paleofluid geochemistry to reconstruct the burial-deformation history of the Meso-Cenozoic carbonate sequence of the Cingoli Anticline (Northern Apennines, central Italy). Four major sets of mesostructures were linked to the regional deformation sequence: (i) pre-folding foreland flexure/forebulge; (ii) fold-scale layer-parallel shortening under a N045 σ1; (iii) syn-folding curvature of which the variable trend between the north and the south of the anticline is consistent with the arcuate shape of the anticline; (iv) the late stage of fold tightening. The maximum depth experienced by the strata prior to contraction, up to 1850 m, was quantified by sedimentary stylolite paleopiezometry and projected on the reconstructed burial curve to assess the timing of the contraction. As isotope geochemistry points towards fluid precipitation at thermal equilibrium, the carbonate clumped isotope thermometry (Δ47) considered for each fracture set yields the absolute timing of the development and exhumation of the Cingoli Anticline: layer-parallel shortening occurred from ~6.3 to 5.8 Ma, followed by fold growth that lasted from ~5.8 to 3.9 Ma.


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