The early Cretaceous orogen-scale Dabieshan metamorphic core complex: implications for extensional collapse of the Triassic HP–UHP orogenic belt in east-central China

Abstract

International audienceThe Dabieshan massif is famous as a portion of the world’s largest HP–UHP metamorphic belt in east-central China that was built by the Triassic North–South China collision. The central domain of the Dabieshan massif is occupied by a huge migmatite-cored dome [i.e., the central Dabieshan dome (CDD)]. Origin of this domal structure remains controversial. Synthesizing previous and our new structural and geochronological data, we define the Cretaceous Dabieshan as an orogen-scale metamorphic core complex (MCC) with a multistage history. Onset of lithospheric extension in the Dabieshan area occurred as early as the commencement of crustal anatexis at the earliest Cretaceous (ca. 145 Ma), which was followed by primary (early-stage) detachment during 142–130 Ma. The central Dabieshan complex in the footwall and surrounding detachment faults recorded a consistently top-to-the-NW shearing. It is thus inferred that the primary detachment was initiated from a flat-lying detachment zone at the middle crust level. Removal of the orogenic root by delamination at ca. 130 Ma came into the extensional climax, and subsequently isostatic rebound resulted in rapid doming. Along with exhumation of the footwall, the mid-crustal detachment zone had been warped as shear zones around the CDD. After 120 Ma, the detachment system probably experienced a migration accommodated to the crustal adjustment, which led to secondary (late-stage) detachment with localized ductile shearing at ca. 110 Ma. The migmatite–gneiss with HP/UHP relicts in the CDD (i.e., the central Dabieshan complex) was product of the Cretaceous crustal anatexis that consumed the deep-seated part of the HP–UHP slices and the underlying para-autochthonous basement. Compared with the contemporaneous MCCs widely developed along the eastern margin of the Eurasian continent, we proposed that occurrence of the Dabieshan MCC shares the same tectonic setting as the “destruction of the North China craton”. However, geodynamic trigger of the Cretaceous continental-scale NW–SE extension in eastern Asia is still a mystery

Cretaceous Episodic Extension in the South China Block, East Asia: Evidence From the Yuechengling Massif of Central South China

“…In fact, this episodic extension has also been recognized in other extensional structures. In the northern part of the SCB, the Tongbai and Dabie Massifs superimposed on the Triassic Qinling‐Dabie orogenic belt both recorded Cretaceous extension and unroofing that accommodate the final exhumation of the lower crustal rocks (Cui et al, ; Hacker et al, ; Ji, Lin, Faure, Shi, et al, ; Ratschbacher et al, ; Webb et al, ; Xu & Wang, ). They share similar kinematics with top‐to‐the NW shearing but indicate different exhumation stories.…”

“…Ar‐Ar cooling ages of Tongbaishan (TBS) yield two stages of deformation at 140–115 and 105–85 Ma, whereas Dabieshan (DBS) shows a dominant age cluster at 140–115 Ma, suggesting that the Early Cretaceous deformation with contemporaneous migmatization and magmatism gave rise to almost all of the exposed rocks (Figure a). However, minor Late Cretaceous cooling ages correspond to later uplifting or thermal perturbation and can thus be linked with the Late Cretaceous extension (D 2 event; Webb et al, ; Ratschbacher et al, ; Ji, Lin, Faure, Shi, et al, ). At the northern margin of the SCB, the early extension seems to have a more widespread impact, because these extensional/magmatic domes, including the Huangling Massif (HL), Qingyang‐Jiuhua plutons (QY‐JH), and Hongzheng MCC (HZ), were formed during Early Cretaceous without later cooling ages (Ji et al, ; Wei, Martelet et al, ; Wei, Chen, et al, ; Zhu, Xie, et al, ).…”

“…This may also lead to the spectacular destruction of the North China Block (NCB) that removed a large amount of lithospheric mantle since the Mesozoic (Chen et al, ; Lin & Wang, ; Wu et al, ; Zhu et al, ). The South China Block (SCB), which was amalgamated with the NCB by the Qinling‐Dabie orogeny, displays a similar extensional scenario (Ji, Lin, Faure, Shi, et al, ; Li et al, ). The Paleo‐Pacific oceanic plate subducted westward beneath the SCB, where voluminous plutonic and volcanic rocks were widespread in the central and eastern regions from 160 to 90 Ma (Li & Li, ; Zhou et al, ).…”

Multiple Emplacement and Exhumation History of the Late Mesozoic Dayunshan‐Mufushan Batholith in Southeast China and Its Tectonic Significance: 2. Magnetic Fabrics and Gravity Survey

“…In eastern China, the Late Mesozoic geological evolution characterized by large-scale intracontinental deformation and magmatism is traditionally referred to as the Yanshanian (i.e., Jurassic-Cretaceous period) cycle (e.g., Davis et al, 2001;Dong et al, 2015;Li et al, 2012;J. It is well acknowledged that Cretaceous metamorphic core complexes (MCCs) are widely developed in the North China Craton (NCC) and its adjacent regions, indicative of a widespread NW-SE extension coeval with lithospheric thinning (e.g., Charles et al, 2012Charles et al, , 2011Ji, Lin, Faure, Shi, et al, 2017;Lin et al, 2015;Lin & Wang, 2006;Liu et al, 2013;T. There, compressional and extensional events have been distinguished by different authors, leading to confusion in understanding the complex tectonic scenarios.…”

“…There, compressional and extensional events have been distinguished by different authors, leading to confusion in understanding the complex tectonic scenarios. It is well acknowledged that Cretaceous metamorphic core complexes (MCCs) are widely developed in the North China Craton (NCC) and its adjacent regions, indicative of a widespread NW-SE extension coeval with lithospheric thinning (e.g., Charles et al, 2012Charles et al, , 2011Ji, Lin, Faure, Shi, et al, 2017;Lin et al, 2015;Lin & Wang, 2006;Liu et al, 2013;T. Wang et al, 2011, timing of the Late Mesozoic extensional tectonics in the SCB remain inconclusive.…”