Numerical modeling of mullions in the Taili high deformation zone, North China: Implications for the rheology of granitic rocks

Li, Zhiyong; Zeng, Zhaofa; Mohammed, Adil S.

doi:10.1016/j.jseaes.2016.11.022

Cited by 4 publications

(4 citation statements)

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“…The intrusion of biotite adamellite into the late Neoarchean granitic gneisses caused partial remelting and migmatization at the contact zone. Strong ductile deformation occurred due to the emplacement of Late Triassic granitic magma (Li et al, 2017). In the deformation zone, a dominant foliation is striking NE, with a general trend of 320-345° and dip of 66-88° (Liang et al, 2015a).…”

Section: ■ Geological Settingmentioning

confidence: 98%

“…The basement rocks in the eastern zone of the North China Craton are composed predominantly of Archean gneisses and syntectonic granitoids (Zhao et al, 1998). A wide variety of boudinage and mullion structures (Li et al, 2017;Wan et al, 2020) are present in the Taili syntectonic migmatite deformation zone of North China, one of many highstrain zones located along the northeastern margin of the North China Craton (Fig. 1).…”

Section: ■ Geological Settingmentioning

confidence: 99%

“…14). The rheology and deformation behavior of rocks in the study area are primarily related to the mineral composition (Liang et al, 2015a(Liang et al, , 2015b and the grain sizes of quartz and feldspar (Li et al, 2017). Differences in competency have caused the bulk layer-parallel extension deformation of the whole deformation zone to be partitioned into outcrop-scale zones that accommodated different amounts of strain.…”

Section: Strain Partitioning During the Deformation Of Migmatitesmentioning

confidence: 99%

“…15A and 15B). The migamatites are significantly different in composition, grain size, and intensity of foliation development, which leads to competence (viscosity) contrast between different domains (e.g., Liang et al, 2015a;Li et al, 2017). The competence contrast was likely to have been controlled by the composition of the migmatites and consequently changed during the different migmatization stages.…”

Section: Effective Viscosity Contrast Of Migmatitesmentioning

confidence: 99%

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Boudinage and the rheology of syntectonic migmatites in the high-strain Taili deformation zone, NE China

Zeng

Liu

2023

Geosphere

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This paper presents a detailed field characterization of boudinage in a high-strain zone several kilometers wide in Northern China to establish relationships between boudin types and rheological contrasts between different parts of migmatites during the migmatization process. This zone contains nearly all types of boudins: foliation boudins, block-torn boudins, pinch-and-swell structures, tapering boudins, object boudins, and modified boudins. These boudinage structures record the different stages of melt-involved and solid-state deformation. The boudinage of migmatites is significantly controlled by the evolving rheological contrasts between the leucosome and melanosome. During the melting stage, the deformation and boudinage of rocks are controlled by the melt fraction. Migmatite strength progressively decreases with increasing melt fraction. The occurrence of melt-filled foliation boudins and melanosome block boudins suggests that the residuum and melanosome are more competent than the leucosome. During solid-state deformation after crystallization, the existence of recrystallized solid-state leucosomes and the intrusion of pegmatites cause the migmatite strength to increase. The relationship is reversed: the leucosome is much more competent than the melanosome. The type and geometry of boudins and pinch-and-swell structures are correlated to the fraction of leucosome in the migmatites. The mechanical strength and strain localization of migmatites after crystallization depend on the presence and volume fraction of the different mineral phases, as well as the mineral grain size. The type and geometry of boudins suggest that the effective viscosity of migmatite can be ranked, from high to low, as: quartz veins; coarse-grained, thick pegmatite; coarse-grained, diatexite migmatite; medium-grained leucosome; and fine-grained melanosome. While experiencing partial melting and migmatization, a rheologically homogeneous protolith is turned into two dominant lithologic domains: a competent diatexite migmatite domain and an incompetent melanosome migmatite domain. Spatially, with the increasing leucosome fraction in migmatites, the migmatite rheology of rock changes from homogeneous to heterogeneous and anisotropic, and then back to homogeneous. The strain distribution likewise changes from uniform to partitioned, and then back to uniform. This evolutionary process of strength and rheological properties of rocks during migmatization may promote strain localization at mid crustal conditions.

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Section: ■ Geological Settingmentioning

confidence: 98%