Computer Science
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995e%26psl.134..359s&link_type=abstract
Earth and Planetary Science Letters, vol. 134, Issue 3-4, pp.359-376
Computer Science
3
Scientific paper
We report major element, trace element, and Nd and Sr isotopic ratios for 35 samples of Late Mississippian-Early Permian Alleghanian granites that intrude the Carolina terrane, Eastern slate belt, Inner Piedmont, and Kiokee belt of the southern Appalachians. Major element compositions indicate that most plutons are high-potassium (K 2 O 4%) metaluminous granites. Initial Nd , depleted mantle model ages, and initial ratios, respectively, of the plutons range from -8.2 to -3.4, 940-1020 Ma, and 0.70642-0.72798 for the Inner Piedmont; -2.3 to +2.0, 660-1130 Ma, and 0.70421-0.71035 for the Kiokee belt; - 2.7 to +2.4, 660-870 Ma, and 0.70353-0.70816 for the Eastern slate belt; and -6.7 to + 1.9, 690-1140 Ma, and 0.70391-0.70739 for the Carolina terrane. The chemical and isotopic data are most consistent with formation of the granites by anatexis of continental crust, rather than derivation from a depleted mantle source. Rocks of the Carolina terrane have Nd (300 Ma) values and Pb isotopic ratios indistinguishable from those of most Alleghanian granites, suggesting it is a likely source. Some Alleghanian granites within the Carolina terrane require a more evolved source than exposed Carolina terrane rocks, suggesting that evolved crust, possibly Grenville basement, occurs structurally below or within the terrane. The chemical and isotopic compositions of granites intruding the Kiokee belt, Eastern slate belt, and Carolina terrane are similar, suggesting that these terranes are geochemically similar. In contrast, Alleghanian granites within the Inner Piedmont have higher initial and lower ratios, indicating that their sources are isotopically more evolved. The virtual absence of Alleghanian plutons with mafic-intermediate compositions, and the lack of geographic trends in chemical and isotopic composition across the orogen, makes a subduction origin for the granites unlikely. The consistency of the geochemical data with a crustal anatectic origin of the granites, together with the observation that they intruded synchronously with Alleghanian thrusting in the Valley and Ridge Province, suggests strongly that they are collisional in origin. The crustal heating events that produced the granites might have been caused by delamination of mantle lithosphere during collision of Laurentia with Gondwana. Alternatively, adequate heating may have occurred by crustal thickening during emplacement of thrust sheets.
Coler David G.
Samson Scott D.
Speer Alexander J.
No associations
LandOfFree
Geochemical and Nd-Sr-Pb isotopic composition of Alleghanian granites of the southern Appalachians: Origin, tectonic setting, and source characterization does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Geochemical and Nd-Sr-Pb isotopic composition of Alleghanian granites of the southern Appalachians: Origin, tectonic setting, and source characterization, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Geochemical and Nd-Sr-Pb isotopic composition of Alleghanian granites of the southern Appalachians: Origin, tectonic setting, and source characterization will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-825856