Early Carboniferous tectonic evolution of the northern Heihe–Nenjiang–Hegenshan suture zone, NE China: Constraints from the mylonitized Nenjiang rhyolites and the Moguqi gabbros

Abstract

The Heihe–Nenjiang–Hegenshan suture zone has long been accepted as the major tectonic boundary between the Xing'an and Songliao blocks and extends through the Great Xing'an Range in NE China, but its location of the northern segment between the Moguqi and Nenjiang areas and its timing remain unclear. We address these issues by presenting zircon LA‐ICP‐MS U–Pb ages, Lu‐Hf isotopes, bulk‐rock major, and trace elemental data for mylonitized rhyolites collected from the Moergenhe Formation in the Nenjiang area and for gabbros of the Moguqi area, respectively. The mylonitized rhyolites, which display an arc‐related geochemical affinity with enrichment in Th and U, and depletion of Nb, Ta, and Ti, and gently right‐tilted rare earth element (REE) patterns (light REE [LREE]/heavy REE [HREE] =4.53–7.60), as well as the εHf (t) values (+6.4 to +11.8) of analyzed zircons, indicate an origin by partial melting of potentially young lower continental crust of a subducting slab. The zircon LA‐ICP‐MS U–Pb data show the formation age of the mylonitized rhyolites is 352.4 Ma. The analyzed gabbros with an emplacement age of 352.6 Ma have high concentrations of Th and U, slightly enriched LREE patterns and relative low LREE/HREE ratios (4.3 to 4.6). These features, together with their high positive εHf (t) values (+7.7 to +15.2), suggest that they were likely derived from the partial melting of a depleted mantle source that was metasomatized by subduction‐related fluids. Combined with the geochemical features of the coeval igneous rocks from the northern Great Xing'an Range, these results reveal that the existence of an early Carboniferous NE‐trending magmatic arc (ca. 350–330 Ma), extending along the west of the Heihe–Nenjiang–Hegenshan suture zone, gives more constraints on the amalgamation of the Xing'an and Songliao blocks along the Nenjiang–Moguqi areas and indicates that the amalgamation should have terminated by at least the end of the early Carboniferous.

Late Devonian to early Carboniferous magmatism in the western Songliao–Xilinhot block, Northeast China: Implications for eastward subduction of the Nenjiang oceanic lithosphere

“…Here, the hornblende gabbros have uniformly high Zr/Y ratios (2.1–2.6) and relatively high Nb/Y ratios (0.19–0.22), similar to those of primitive mantle compositions (Figure a), indicating that partial melting of a primitive mantle source may also have been involved in the formation of the primitive magma. Regionally, our samples are comparable with coeval mafic–ultramafic rocks from the central and northern Great Xing'an Range, which plot mainly in the primitive mantle and enriched mantle fields (Feng et al, ; Wang et al, 2013; Zhou et al, 2015; Figure a). However, those from the southern Great Xing'an Range show a lower than mantle source material signature (Song et al, ; Figure a).…”

“…(f) Ba/Th versus (La/Sm) N diagram. Data for the northern Great Xing'an Range are from Zhou et al, , central Great Xing'an Range from Feng et al, and Wang et al, 2013, and southern Great Xing'an Range from Song et al, . CAB, continental arc basalt; CLM, continental lithospheric mantle; IAT, island arc tholeiite; N‐MORB, normal mid‐oceanic ridge basalt; OIB, ocean island basalt [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Numerous studies have investigated the evolution of interaction between the XAC and the SXB (e.g., Feng et al, ; Liu et al, 2017, 2019; Li et al, ; Ma et al, , 2019; Zhang et al, 2018). However, most of those studies focused on the amalgamation time and suture zone location of the two geological units (e.g., Feng et al, ; Liu et al, 2017, 2019; Ma et al, , 2019). Tectonic aspects such as regime type, tectonic style (e.g., subduction polarity), and associated magmatism have been less well studied.…”

“…1980). Data for the northern Great Xing'an Range are from Zhou et al, , central Great Xing'an Range from Feng et al, and Wang et al, 2013, and southern Great Xing'an Range from Song et al, . CAB, continental arc basalt; EMORB + WPT, enrichment mid‐oceanic ridge basalt and within‐plate tholeiite; IAT, island arc tholeiite; N‐MORB, normal mid‐oceanic ridge basalt; ORG, ocean ridge granites; post‐COLG, postcollision granites; syn‐COLG, syn‐collision granites; WPA, within‐plate alkali; VAB, volcanic arc basalt; VAG, volcanic arc granites; WPAB, within‐plate alkali basalt; WPG, within‐plate granites [Color figure can be viewed at wileyonlinelibrary.com]…”

Geochronology and geochemistry of the Carboniferous felsic rocks in the central Great Xing'an Range, NE China: Implications for the amalgamation history of Xing'an and Songliao–Xilinhot blocks

“…The HHS is generally seen as the suture zone between the XB and SXB (Feng et al, , ; Han et al, , ; Liu et al, ; J. B. Zhou & Wilde, ; J.…”