1. Geochronology, geochemistry, and petrogenesis of Early Cretaceous highly differentiated I-type granites in the central Great Xing'an Range, northeastern China
- Author
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Lan, Li-xue, Dong, Yu, Ge, Wen-chun, Gao, Yan, Ji, Zheng, Jing, Yan, Bi, Jun-hui, and Zhou, Hong-ying
- Subjects
Granite -- Environmental aspects ,Geochronology -- Research ,Geochemistry -- Research ,Petrogenesis -- Research ,Geological research ,Mountains -- Environmental aspects ,Earth sciences - Abstract
In this study, we undertook zircon U--Pb dating and Hf isotopic and whole-rock geochemical analysis of Mesozoic granites from the Zhalantun and Arxan areas of the Great Xing'an Range, northeastern China. Zircon U--Pb dating of four samples indicates they formed in the Early Cretaceous (ca. 140.7-130.0 Ma). Geochemically, the samples have high silica (74.00-77.29 wt.%) and total alkali (8.52-8.90 wt.%) and low CaO (0.21-0.71 wt.%), MgO (0.06-0.48 wt.%), and [P.sub.2][O.sub.5] (0.01-0.06 wt.%) contents and exhibit the weakly peraluminous (A/CNK = 0.98-1.06) and high-K calc-alkaline characteristics, with highly differentiated I-type granite affinities (differentiation index = 93.19-96.93). The studied granites are enriched in light rare earth and large ion lithophile elements and depleted in heavy rare earth and high field strength elements. Their zircon [[epsilon].sub.Hf](t) values are mainly positive (+2.49 to +11.64) and yield two-stage Hf model ages of 1023-445 Ma. The geochemical and isotopic data indicate they might have been derived from the partial melting of medium- to high-K basaltic crust material during the Mesoproterozoic to Phanerozoic. They underwent fractional crystallization in the magma evolution process, and K-feldspar and plagioclase were the major crystallization phases. Combined with the temporal--spatial migration of the Mesozoic magmatic events in the whole northeastern China, we propose that the generation of Early Cretaceous highly differentiated I-type granites in the central Great Xing'an Range was associated with the delamination effect caused by the roll-back of the Paleo-Pacific plate. Key words: central Great Xing'an Range, Early Cretaceous, highly differentiated I-type granites, zircon U--Pb--Hf isotopes, Paleo-Pacific plate. Nous avons effectue la datation U--Pb sur zircons et l'analyse geochimique des isotopes de Hf et sur roche totale de granites mesozoiques des regions de Zhalantun et d'Arxan de la chaine du Grand Xing'an (nord-est de la Chine). La datation U--Pb sur zircons de quatre echantillons indique qu'ils se sont formes au Cretace precoce (vers 140,7-130,0 Ma). Du point de vue geochimique, les echantillons ont de fortes teneurs en silice (74,00-77,29 % en poids) et en alcalis totaux (8,52-8,90 % en poids) et de faibles teneurs en CaO (0,21-0,71 % en poids), MgO (0,06-0,48 % en poids) et [P.sub.2][O.sub.5] (0,01-0,06 % en poids) et presentent des caracteres legerement hyperalumineux (A/CNK = 0,98-1,06) et calcoalcalins riches en K, ainsi que des affinites avec des granites de type I fortement differencies (indice de differentiation = 93,19-96,93). Les granites etudies sont enrichis en terres rares legeres et en elements lithophiles a grand rayon ionique et appauvris en terres rares lourdes et en elements a forte liaison atomique. Les valeurs de [[epsilon].sub.Hf](t) de leurs zircons sont principalement positives (de +2,49 a +11,64) et donnent des ages de modele Hf en deux etapes de 1023-445 Ma. Les donnees geochimiques et isotopiques indiquent qu'ils pourraient avoir ete derives de la fusion partielle de croute basaltique a teneur en K intermediaire a forte durant l'intervalle du Mesoproterozoique au Phanerozoique. Ils ont subi une cristallisation fractionnee durant le processus d'evolution magmatique, le feldspath K et le plagioclase etant les principaux produits de la cristallisation. Nous proposons que, combinee a la migration dans le temps et l'espace des episodes magmatiques mesozoiques a la grandeur du nord-est de la Chine, la production de granites de type I hautement differencies au Cretace precoce dans la chaine du Grand Xing'an centrale etait associee a l'effet de delamination cause par le recul de la plaque paleo-pacifique. [Traduit par la Redaction] Mots-cles : chaine du Grand Xing'an centrale, Cretace precoce, granites de type I fortement differencies, isotopes de U--Pb--Hf de zircons, plaque paleo-pacifique., Introduction Widespread magmatic events took place in northeastern China (NE China) during the Phanerozoic (Wu et al. 2000, 2002, 2006, 2007, 2011; Ge et al. 2005, 2007; Liu et al. [...]
- Published
- 2022
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