Early Jurassic subduction of the Paleo-Pacific Ocean in NE China: Petrologic and geochemical evidence from the Tumen mafic intrusive complex

Lithos ◽  
2015 ◽  
Vol 224-225 ◽  
pp. 46-60 ◽  
Author(s):  
Feng Guo ◽  
Hongxia Li ◽  
Weiming Fan ◽  
Jingyan Li ◽  
Liang Zhao ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Early Jurassic ◽  
Intrusive Complex ◽  
Ne China ◽  
Geochemical Evidence

Geochemistry and geochronology of OIB-type, Early Jurassic magmatism in the Zhangguangcai range, NE China, as a result of continental back-arc extension

2018 ◽  
Vol 158 (1) ◽  
pp. 143-157 ◽  
Author(s):  
Guangying Feng ◽  
Yildirim Dilek ◽  
Xiaolu Niu ◽  
Fei Liu ◽  
Jingsui Yang
Keyword(s):  
East Asia ◽  
Trace Element ◽  
Partial Melting ◽  
Early Jurassic ◽  
Ne China ◽  
Mafic Rocks ◽  
Asthenospheric Mantle ◽  
Trace Element Contents ◽  
Pacific Slab ◽  
Back Arc

AbstractThe Zhangguangcai Range in the Xing’an Mongolian Orogenic Belt, NE China, contains Early Jurassic (c. 188 Ma) Dabaizigou (DBZG) porphyritic dolerite. Compared with other island-arc mafic rocks, the DBZG dolerite is characterized by high trace-element contents, relatively weak Nb and Ta enrichments, and no Zr, Hf or Ti depletions, similar to OIB-type rocks. Analysed rocks have (87Sr/86Sr)i ratios of 0.7033–0.7044, relatively uniform positive ɛNd(t) values of 2.3–3.2 and positive ɛHf(t) values of 8.5–17.1. Trace-element and isotopic modelling indicates that the DBZG mafic rocks were generated by partial melting of asthenospheric mantle under garnet- to spinel-facies conditions. The occurrence of OIB-like mafic intrusion suggests significant upwelling of the asthenosphere in response to lithospheric attenuation caused by continental rifting. These processes occurred in an incipient continental back-arc environment in the upper plate of a palaeo-Pacific slab subducting W–NW beneath East Asia.

scholarly journals Genesis of the Weizigou Au Deposit, Heilongjiang Province, NE China: Constraints from LA-ICP-MS Trace Element Analysis of Magnetite, Pyrite and Pyrrhotite, Pyrite Re-Os Dating and S-Pb Isotopes

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1380
Author(s):  
Yu Gao ◽  
Yujie Hao ◽  
Siyu Lu
Keyword(s):  
Trace Element Analysis ◽  
Isotopic Analysis ◽  
Early Jurassic ◽  
Heilongjiang Province ◽  
Ne China ◽  
Element Analysis ◽  
Hydrothermal Origin ◽  
Icp Ms ◽  
Zn Content ◽  
Mineralization Age

The Weizigou Au deposit in Heilongjiang Province, NE China, located in the southern Jiamusi Massif, shows similarities to IOCG deposits. To determine the mineralization age, sources of ore-forming materials and genetic type, pyrite Re-Os dating, S-Pb isotopic analysis, in situ sulfur analysis and LA-ICP-MS analysis of trace elements in magnetite, pyrite and pyrrhotite were conducted. Four pyrite samples yielded a Re-Os isochron age of 197 ± 11 Ma, implying the occurrence a metallogenic event in the Early Jurassic. The δ34S values of sulfides display a relatively narrow range from 4.70‰ to 12.83‰ (mainly 9.90‰ to 12.83‰), which may be accounted for the extensively exposed granitic gneiss and meta-gabbro, with δ34S values of 7.44‰ to 8.44‰ and 4.37‰ to 10.54‰, respectively. Sulfide lead isotopic compositions have 206Pb/204Pb = 18.605–20.136, 207Pb/204Pb = 15.637–15.710 and 208Pb/204Pb = 38.534–39.129, indicating that the lead was derived from a mixed source. Magnetite has the characteristics of a lower Ti content and higher Zn content, indicating that it should be of hydrothermal origin, which may be related to IOCG-type mineralization. Pyrite and pyrrhotite have a Co/Ni ratio greater than 1 and a lower As content, indicating that they are of magmatic hydrothermal origin. Integrating the above analysis results, we inferred that the Weizigou Au deposit experienced the IOCG-type mineralization in the Middle-Late Permian, associated with magmatic-hydrothermal mineralization in the Early Jurassic.

Cretaceous Black Shales in the Pacific: The Equatorial Position Hypothesis

2021 ◽  
Author(s):  
Max J. Bouwmeester ◽  
Lydian Boschman ◽  
Nienke Berends ◽  
Jeremy D. Owens ◽  
Ben C. Gill ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Organic Carbon ◽  
Ocean Basin ◽  
Black Shales ◽  
Equatorial Position ◽  
Scientific Drilling ◽  
Geochemical Evidence ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Oceanic Anoxia

<p>Although anoxia is rare in modern oceans, the marine stratigraphic record is punctuated by sedimentary and geochemical evidence for episodes of widespread oceanic anoxia. The last time in Earth history that a large volume of the ocean became anoxic was in the middle Cretaceous: black organic-carbon-rich muds were repeatedly preserved on the deep seafloor during oceanic anoxic events (OAEs).</p><p>Sedimentary and geochemical evidence for oceanic anoxia during OAEs comes mainly from the Atlantic and Tethys Oceans. Data from the Pacific Ocean, which was the largest ocean basin in the middle Cretaceous, is scarce and equivocal. Based on black shales deposited at depths of about 500–1500 m on seamounts, Monteiro et al. (2012) have suggested that at least 50 vol% of the ocean was anoxic at the climax of Cretaceous oceanic anoxia during the late Cenomanian. They also included a single black shale at DSDP Site 585 in the Mariana Basin as evidence for anoxia in the deep Pacific. We will show, however, that this is a mud turbidite reworked from shallower water.</p><p>For this study, we reviewed all available data and publications from scientific drilling that recovered Cretaceous sediments in the Pacific Ocean. The little available Cretaceous record from the Pacific consists mainly of well-oxidized sediments. The exceptions are black shales that occur at depths of about 500–1500 m on seamounts. Takashima et al. (2011) have shown that the Asian and North American continental margins of the Pacific were indeed oxic for most of the late Cenomanian OAE. </p><p>We used a new paleomagnetic reconstruction of the Pacific plate back to 150 Ma to show that all investigated Cretaceous organic-carbon-rich sediments in the Pacific Ocean were deposited while the site was located in the Equatorial Divergence Zone (10°S to 10°N). We therefore argue that organic matter deposition in the Pacific Ocean might not have been directly related to OAEs, but rather be associated with the passage of seamounts beneath the equatorial belt of high productivity.</p><p>Several authors have challenged suggestions that OAEs were characterized by globally pervasive anoxic deep water and pointed to the difficulty in sustaining whole-ocean anoxia, even in warm oceans. We agree and our results show that oceanic anoxia in the Pacific is a local phenomenon superposed on a global trend of expanded oxygen minima in the ocean.</p>

Early Jurassic granodiorite‐monzogranite‐granite suite in the Zhangguangcai Range , NE China: Implications for melting of newly accreted arc crust

2021 ◽  
Author(s):  
Wenbao Wang ◽  
Guihu Chen ◽  
Cunzhu Wang ◽  
Renzhi Zhu ◽  
Jingwen Chen ◽  
...  
Keyword(s):  
Early Jurassic ◽  
Ne China ◽  
Granite Suite
Sign in / Sign up

Export Citation Format

Share Document