Petrogenesis Of Granitoid Rocks Research Articles

Petrogenesis and tectonic implications of the Mesozoic granitoid intrusions in the eastern Liaoning Peninsula, NE China

Mesozoic magmatic rocks are widely distributed in the eastern region of the North China Craton (NCC), providing important information for understanding the Mesozoic tectonic regimes in this area. This paper reports newly obtained geological, geochemical, and zircon U-Pb-Lu-Hf isotope data for the Xiaoheishan-Daheishan intrusion (XDI) and the Yanghezhen-Dayingzhen intrusion (YDI) newly identified from Precambrian metamorphic basement range in the eastern Liaoning Peninsula, and provides a case study demonstrating that the petrogenesis of granitoid rocks was closely related to the tectonic regimes. The Middle-Late Jurassic XDI granitoids commonly have the adakite-like geochemical characteristics and their primary magma was derived from the partial melting of mafic rocks and Neoarchean tonalites in the thickened lower crust. The Early Cretaceous YDI granitoid rocks generally show diversified geochemical characteristics and their primary magma was generated by the partial melting of Paleoproterozoic metagreywackes and Neoarchean tonalites in the lower crust with minor addition of mantle-derived magma. These differences indicate that the granitoid magmatism in the eastern Liaoning Peninsula has occurred a significant variation during the Jurassic to Cretaceous. The variation of late Mesozoic granitoid magmatism may be responses to the regional tectonic transition from compression to extension in the eastern Liaoning Peninsula, which is induced by the geodynamic regime of the Paleo-Pacific Plate from low-angle subduction to slab rollback.

Deciphering the Mesoarchean to Neoarchean history of crustal growth and recycling in the Caochang region of the Eastern Hebei Province, North China Craton using combined zircon U–Pb and Lu-Hf isotope analysis

In Archean cratons, the end of the Archean aeon (3.0–2.5 Ga) is marked by a considerable diversification in both the nature and petrogenesis of granitoid rocks. We reported the studies of a series of Mesoarchean-Neoarchean diorite and tonalite–trondhjemite–granodiorite (TTG) and granitic gneisses in the Caochang area, Eastern Hebei region of the North China Craton. Combined zircon U-Pb and Lu-Hf isotope analyses and CL imaging analysis reveal three major magmatic events (3.2-3.0 Ga, 2.9-2.8 Ga, ~2.5 Ga) and one major metamorphic overprint (~2.5 Ga). The close temporal relationship for different zircon domains reveals that the late-Neoarchean crustal materials were recycled or reworked immediately after their formation, immediately followed by ~2.5 Ga recrystallized metamorphism.The voluminous mantle-derived mafic rocks indicate that the 2.5-2.6 Ga is an important period of crustal addition in the Eastern Hebei region. The peak of Hf model age and the widespread Mesoarchean or Paleoarchean crustal materials in Eastern Hebei may point to another important period of crustal addition before the Neoarchean.

The diversity and evolution of late-Archean granitoids: Evidence for the onset of “modern-style” plate tectonics between 3.0 and 2.5Ga

The end of the Archean aeon (3.0–2.5 Ga) was a period of fundamental change in many aspects of the geological record. In Archean cratons, this timespan is marked by a considerable diversification in both the nature and petrogenesis of granitoid rocks. In this article, we review the nature, petrogenesis and global evolution of late-Archean granitoids and discuss their geodynamic significance. Late-Archean granitoids can be classified into four groups: (1) volumetrically-dominant and juvenile tonalites, trondhjemites and granodiorites (TTGs), whose geochemistry is consistent with an origin through partial melting of meta-igneous mafic rocks at various pressures; (2) Mg-, Fe- and K-rich, metaluminous (monzo)diorites and granodiorites, referred to as sanukitoids s.l., which derive primarily from hybridization between mantle peridotite and a component rich in incompatible elements; (3) peraluminous and K-rich biotite- and two-mica granites, formed through melting of older crustal lithologies (TTGs and meta-sediments, respectively); and (4) hybrid high-K granites with mixed characteristics from the first three groups. The chronology of granitoid emplacement in late-Archean times is different from one craton to another but, in general, follows a very specific two-stage sequence: (1) a long period (0.2–0.5 Ga) of TTG emplacement; (2) a shorter period (0.02–0.15 Ga) during which all other granitoid types were generated. We propose that this sequence represents the first global subduction–collision cycle in the Earth's history. Although possibly present in the geological record prior to 3.0 Ga, such mechanisms became progressively prevalent on a planetary scale only between 3.0 and 2.5 Ga, indicating that the late-Archean geodynamic changes resulted from the global initiation of “modern-style” plate tectonics. The Archean–Proterozoic transition thus represents a major change in the mechanisms of the Earth's heat loss: before 3.0–2.5 Ga, it took place by large-scale magmatic differentiation characterized by generation of proto-continents that underwent crustal maturation locally, but without obvious cyclic activity on a planetary scale. After this, heat loss became accommodated by plate tectonics and global Wilson subduction–collision cycles. These changes were the consequence of the Earth's cooling, which in turn controlled a number of different parameters locally (thickness, temperature, volume and rheology of the crust). This explains why the changes took place over a short timespan (~ 0.5 Ga) relative to the Earth's history, but at different times and with different characteristics from one craton to another.

Geochronology and petrogenesis of granitoid rocks from the Goryczkowa Unit, Tatra Mountains (Central Western Carpathians)

Abstract The geochemical characteristics as well as the LA-MC-ICP-MS U-Pb zircon age relationship between two granitoid suites found in the Goryczkowa crystalline core in the Western Tatra Mountains were studied. The petrological investigations indicate that both granitoid suites were emplaced at medium crustal level, in a VAG (volcanic arc granites) tectonic setting. However, these suites differ in source material melted and represent two different magmatic stages: suite 1 represents a high temperature, oxidized, pre-plate collision intrusion, emplaced at ca. 371 Ma while suite 2 is late orogenic/anatectic magma, which intruded at ca. 350 Ma. These data are consistent with a period of intensive magmatic activity in the Tatra Mountain crystalline basement. The emplacement of granitoids postdates the LP-HT regional metamorphism/ partial melting at ca. 387 Ma and at 433-410 Ma, imprinted in the inherited zircon cores.

Petrogenesis of granitoid rocks at the northern margin of the Eastern Ghats Mobile Belt and evidence of syn-collisional magmatism

The northern margin of the Eastern Ghats Mobile belt against the Singhbhum craton exposes granitic rocks with enclaves from both the high-grade and low-grade belts. A shear cleavage developed in the boundary region is also observed in these granitoids. Field features and petrography indicate syn-tectonic emplacement of these granitoids. Petrology-mineralogy and geochemistry indicate that some of the granitoids are derived from the high-grade protoliths by dehydration melting. Others could have been derived from low-grade protoliths. Moreover, microstructural signatures in these granitoids attest to their syn-collisional emplacement.