Geochronology, geochemistry, and its geological significance of the Permian Mandula mafic rocks in Damaoqi, Inner Mongolia

Abstract

The Hujierte-Chaganhadamiao volcanic-plutonic sequence is located in the Mandula area of northern Damaoqi, Inner Mongolia. It contains mainly mafic volcanics, with several ultramafic blocks in its central part and mafic-intermediate intrusions in the east. The zircon U-Pb ages of the gabbro and basalt samples are 278.5±3.0 Ma (MSWD=0.66) and 273.7±1.0 Ma (MSWD=0.36), respectively. These ages constrain the magmatism occurred in the Early Permian. The Mandula Permian mafic rocks are characterized by low abundances of REE and slightly LREE-enriched chondrite-normalized N-MORB-type REE patterns. And these mafic samples have high ( 143 Nd/ 144 Nd) i (0.51262-0.51270), relatively high positive ε Nd (t) (3.4-8.0), and high Mg # (49-54), suggesting derivation from the depleted asthenosphere mantle source. But they also show the enrichment in large ion lithophile elements (LILE, e.g. Rb, Ba and Sr), depletion in high field strength elements (HFSE); distinctly negative Nb, Ta anomalies and slightly negative P, Ti anomalies; high ( 87 Sr/ 86 Sr) i (0.70490-0.70537), low ( 206 Pb/ 204 Pb) i (17.39-17.93).All of these resemble the characteristics of the enriched mantle source or involvement of arc materials in the magma genesis. Furthermore, as shown in the correlation plots of ε Nd (t) vs ( 87 Sr/ 86 Sr) i , ( 206 Pb/ 204 Pb) i vs ( 207 Pb/ 204 Pb) i and ( 208 Pb/ 204 Pb) i , La/Ba La/Nb vs La/Nb, and La/Nb ratio, the magma source could have been experienced the contamination and metasomation from the previous subduction process. And the positive correlation between the selected major oxides and trace elements could be explained by the contamination from continental crust and arc materials during the magmatic emplacement. Combined with the distinct geochemistry features of Mandula mafic samples and many previous researches in the study area, the Early Permian magmatism in Mandula occurred under an extensional rift setting, and a juvenile ocean basin probably had already been formed after further development. Mandula, zircon SHRIMP U-Pb age, Permian, geochemistry, extensional settingCitation:Chen C, Zhang Z C, Guo Z J, et al. Geochronology, geochemistry, and its geological significance of the Permian Mandula mafic rocks in Damaoqi,

Did the Paleo‐Asian Ocean between North China Block and Mongolia Block exist during the late Paleozoic? First paleomagnetic evidence from central‐eastern Inner Mongolia, China

“…In addition, a review of the literatures concerning Permian magmatism around these two localities has shown a peak emplacement age at ca. 274 Ma (Figure a) [ Zhang et al ., ; Liu et al ., ; Chen et al ., ]. The solo reversed polarity and the estimated age of this remagnetization coincide with timing and features of the PCRS.…”

“…To the north of Linxi County, three sites of tuff and basalt from the Lower Permian Dashizhai Formation (P 1 d) and three sites of sandstone from the Upper Permian Linxi Formation (P 3 l) were collected (Figure g and Table ). The Dashizhai Formation is composed of volcanic rocks erupted between 285 and 270 Ma, which belong to the major Late Paleozoic magmatic event widespread in Inner Mongolia [ Zhang et al ., ; Liu , ; Chen et al ., ]. The Linxi Formation is composed of fluvial conglomerate at the bottom with pebbles of volcanic rocks of Dashizhai Formation, covered by approximately 4000 m thick black mudstone and dark yellowish siltstone/sandstone of fluvial‐lacustrine facies [ Mueller et al ., ].…”

“…[], referred as Inner Mongolia Block (IMB) in this paper. After that, this region underwent an extensional setting characterized by Early Permian alkine A‐type granitoids and bimodal volcanic rocks [ Zhang et al ., ; Jahn et al ., ; Chen et al ., ] and extension‐related sedimentation [ Tang , ]. However, based on disputable geochemical interpretations, and occurrence of the Permian marine sediments, some authors hypothesized that the Paleo‐Asian Ocean has existed through the late Paleozoic, until the Late Permian when NCB and MOB collided [ Chen et al ., ; Xiao et al ., ; Johnson et al ., ; Heumann et al ., ].…”

Variable sediment flux in generation of Permian subduction-related mafic intrusions from the Yanbian region, NE China

“…Several hypotheses, including the middle Devonian (e.g., Xu et al, 2013a), between the late Devonian and early Carboniferous (e.g., Tang, 1990), or even in the late Permian to Triassic (e.g., Zhou and Wilde, 2013;Eizenhöfer et al, 2014;Wilde, 2015), have been proposed. In NE China, especially in the central Mongolia, the Permian mafic rocks show geochemical and isotopic features of N-MORBs and E-MORBs, reflecting the existence of oceanic basin at that time (Chen et al, 2012;Li et al, 2015). Permian arc magmatism along the northern margin of the North China Craton suggested a Cordillera-type active continental margin related to subduction of the paleo-Asian Ocean (Zhang et al, 2009).…”

Sedimentological and geochronological constraints on the Carboniferous evolution of central Inner Mongolia, southeastern Central Asian Orogenic Belt: Inland sea deposition in a post-orogenic setting

“…The CAOB formed by complicated subduction-accretion processes, with various fragments including microcontinents, island arcs, ophiolite complexes, seamounts, oceanic plateaus, and accretionary prisms (Windley et al, 2007;Safonova et al, 2011;Choulet et al, 2012;Wilhem et al, 2012;Safonova and Santosh, 2014). After the accretion and collision, the former united fragments re-activated, with intra-plate magmatism and deposition occurring in the extensional zones (Tang, 1990;Hong et al, 1994;Yarmolyuk et al, 2008;Zhang et al, 2008;Jahn et al, 2009;Yuan et al, 2010;Han et al, 2011;Chen et al, 2012;Yu et al, 2013). In this case study, we chose the north margin of North China Craton (NCC), located in the southeast of CAOB, to decipher the transition between accretion and post-accretional extension.…”