scholarly journals New identification and significance of Early Cretaceous mafic rocks in the interior South China Block

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hui-Min Su ◽  
Shao-Yong Jiang ◽  
Jia-Bin Shao ◽  
Dong-Yang Zhang ◽  
Xiang-Ke Wu ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
South China ◽  
Distribution Patterns ◽  
Systematic Investigation ◽  
Element Distribution ◽  
Trace Element Distribution ◽  
South China Block ◽  
Mafic Rocks ◽  
Late Mesozoic ◽  
O Isotopes

AbstractEarly Cretaceous mafic rocks are first reported in the northern Guangxi region from the western Qin-Hang belt in the interior South China Block. A systematic investigation of zircon U–Pb dating, whole-rock geochemistry, Sm–Nd isotopes and zircon Hf–O isotopes for these mafic rocks reveals their petrogenesis and the mantle composition as well as a new window to reconstruct lithospheric evolution in interior South China Block during Late Mesozoic. Zircon U–Pb dating yielded ages of 131 ± 2 Ma to 136 ± 2 Ma for diabase and gabbro from Baotan area, indicating the first data for Early Cretaceous mafic magmatism in the western Qing-Hang belt. These mafic rocks show calc-alkaline compositions, arc-like trace element distribution patterns, low zircon εHf(t) of − 9.45 to − 6.17 and high δ18O values of + 5.72 to + 8.09‰, as well as low whole-rock εNd(t) values of − 14.27 to − 9.53. These data suggest that the studied mafic rocks are derived from an ancient lithospheric mantle source that was metasomatized during Neoproterozoic subduction. Thus, the occurrence of these mafic rocks indicates a reactivation of Neoproterozoic subducted materials during an extension setting at Late Mesozoic in the western Qin-Hang belt, an old suture zone that amalgamates the Yangtze and Cathaysia blocks.

Magmatic‐Hydrothermal Alteration Mechanism for Late Mesozoic Remagnetization in the South China Block

2019 ◽  
Vol 124 (11) ◽  
pp. 10704-10720 ◽  
Author(s):  
Liang Gao ◽  
Qingfei Wang ◽  
Jun Deng ◽  
Fangge Chen ◽  
Shihong Zhang ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
South China ◽  
South China Block ◽  
The South ◽  
Late Mesozoic

Petrogenesis of Silurian ultramafic–mafic plutons in southern Jiangxi: implications for the Wuyi–Yunkai orogen, South China

2020 ◽  
pp. 1-16
Author(s):  
Jie Yang ◽  
Wei Liu ◽  
Zuozhen Han ◽  
Zuoxun Zeng ◽  
Le Wan ◽  
...  
Keyword(s):  
South China ◽  
Lithospheric Mantle ◽  
First Episode ◽  
Jiangxi Province ◽  
South China Block ◽  
The South ◽  
Mafic Rocks ◽  
Formation And Evolution ◽  
Early Palaeozoic ◽  
T Values

Abstract The South China Block is one of the largest continental blocks located on the East Asian continent. The early Palaeozoic Wuyi–Yunkai orogen of the South China Block (known as the Caledonian orogen in Europe) is a major orogenic belt in East Asia and represents the first episode of extensive crustal reworking since Neoproterozoic time. Although this orogen is key to deciphering the formation and evolution of the South China Block, details about the orogen remain poorly defined. The Songshutang and Wushitou ultramafic–mafic units in southern Jiangxi Province, South China, have 206Pb–238U ages of c. 437 Ma, suggesting a Silurian formation age. All the Songshutang and Wushitou ultramafic–mafic rocks show relatively flat chondrite-normalized rare earth element patterns, depletions in Nb, Ta, Zr, Hf and Ti, and low ϵNd(t) values from −9.12 to −5.49 with negative zircon ϵHf(t) values from −10.84 to −2.58, resembling a typical arc magma affinity. Geochemical and isotopic data indicate that the newly identified ultramafic–mafic rocks, along with the reported Silurian mafic rocks in South China, possibly originated from the similar partial melting of an ancient subducted slab, fluid/sediment and metasomatized lithospheric mantle with varying degrees of fractional crystallization. In conjunction with other records of magmatism and metamorphism in South China, a late-orogenic extensional event led to the melting of the sub-continental lithospheric mantle in Silurian time and generated ultramafic–mafic rocks with a limited distribution along the Wuyi–Yunkai orogen and widespread late-orogenic granitic plutons in the South China Block.

Subduction polarity of the Ailaoshan Ocean (eastern Paleotethys): Constraints from detrital zircon U-Pb and Hf-O isotopes for the Longtan Formation

2019 ◽  
Vol 132 (5-6) ◽  
pp. 987-996
Author(s):  
Xiao-Ping Xia ◽  
Jian Xu ◽  
Chao Huang ◽  
Xiaoping Long ◽  
Meiling Zhou
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
South China Block ◽  
The South ◽  
Forearc Basin ◽  
Isotopic Signatures ◽  
Northeastern Japan ◽  
O Isotopes ◽  
A Minor ◽  
Back Arc

Abstract The Paleotethys Ailaoshan Ocean separated the South China and Indochina blocks during the late Paleozoic. Uncertainty remains regarding subduction of this ocean—whether it was subducted eastward beneath the South China block or westward beneath the Indochina block. In this study, we present new detrital zircon U-Pb age, and Hf and O isotope data from the Longtan Formation, which was recognized to be deposited before the ocean closed. Our results show that the formation can be divided into three units: Unit 1 is distributed west of the suture and dominates the area; it contains major age peaks at 290–250 Ma and minor multiple old age peaks. Unit 2 consists of a minor distribution west of the suture, and it shows a dominant 250 Ma age peak; old zircons are very few or not present. Their Hf and O isotopic signatures are similar to those of unit 1. Unit 3 is distributed east of the suture and is characterized by a single distinct ca. 240 Ma age peak with almost no Precambrian zircons. We interpret that units 1 and 2 were likely deposited in a back-arc and forearc basin, respectively, and a volcanic arc developed on the eastern margin of the Indochina block, similar to the present-day northeastern Japan arc. Meanwhile, unit 3 was likely deposited in a forearc basin on the western margin of the South China block. Therefore, the Ailaoshan Ocean may undergone bipolar subduction both westward and eastward beneath the Indochina and South China blocks, respectively.

scholarly journals Petrographical and Geochemical Characteristics of Magmatic Rocks in the Northwestern Siberian Traps Province, Kulyumber River Valley. Part II: Rocks of the Kulyumber Site

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 415
Author(s):  
Nadezhda Krivolutskaya ◽  
Boris Belyatsky ◽  
Bronislav Gongalsky ◽  
Alexander Dolgal ◽  
Andrey Lapkovsky ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Element Distribution ◽  
River Valley ◽  
Geochemical Data ◽  
Trace Element Distribution ◽  
Mafic Rocks ◽  
Inductively Coupled ◽  
Magmatic Rocks ◽  
Magma Sources ◽  
Siberian Trap

The origin of the Siberian trap province is under discussion even though numerous models of its formation have been created over the last three decades. This situation is mainly due to lack of modern geochemical data on magmatic rocks around the province. These data are a very important tool to reconstruct of magmatic evolution within the province in time and space and to understand a mechanism of province formation. Geochemical study has only been carried out so far for the Norilsk and Meimecha–Kotuy areas. For the first time, we have studied the geochemical and mineralogical characteristics of magmatic rocks at the Kulyumber river valley located 150 km to south from the Norilsk ore district, in the junction of the Tunguska syneclise and Norilsk–Igarka zone. It comprises three sites, i.e., Khalil, Kaya, and Kulyumber. The geochemical data on the magmatic rocks of the Khalil and Kaya sites were published earlier (Part I). This article (Part II) regards geochemical and mineralogical data on igneous rocks at the Kulyumber site. Seventeen intrusive bodies (41 samples) and six samples of sedimentary rocks were studied by X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). Isotopes analyses (Sr, Nd, Pb) were conducted for 12 samples. These data were compared with data for intrusions of the Norilsk area, the Dzhaltulsky massif, Kureyka river, and intrusions in Angara river valley published earlier. The whole list of analyses includes 102 items. Three groups of intrusive rocks were recognized: (1) Mafic rocks with elevated K2O without negative Ta-Nb and Pb-positive anomalies, with (Gd/Yb)n = 2.0 and εNd = −1.0; attributed to a new Kulyumbinsky complex; (2) subalkaline rocks with elevated SiO2,TiO2, P2O5, and K2O with small negative Ta-Nb and positive Pb anomalies and (Gd/Yb)n = 1.8, εNd = −3.8; Ergalakhsky complex; and (3) mafic rocks with strong Ta-Nb and Pb anomalies and (Gd/Yb)n = 1.2–1.4, εNd = +0.4–+2.2. The third group is rather nonhomogeneous and includes intrusions of the Norilsk, Kuryesky, Katangsky, Ogonersky, and Daldykansky complexes differing in MgO content and trace element distribution (values of Ta-Nb, Pb, and Sr anomalies). Three groups of intrusive bodies had different magma sources and different condition of crystallization reflecting their origin in rift and platform regimes.

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