Magma Genesis and Mantle Sources in the Easter Hotspot-Easter Microplate System

Rb-Sr, Sm-Nd and U-Th-Pb isotopic data for Precambrian granitoids (i.e. granites and intermediate calc-alkaline plutonic rocks) from Greenland, Scotland and Zimbabwe are used to assess the relative contributions to magma genesis of various source materials. Ancient continental crustal contributions are identified by negative e N d values in the magmas at time of formation. Initial 87 Sr/ 86 Sr (Sr 1 ,) values identify crustal contributions as derived from deep (low Rb/Sr) or upper (high Rb/Sr) crust. Pb isotopic data, expressed as model ( 238 U / 204 Pb) values, permit the distinction between deep (low U/Pb) and upper (high U/Pb) crustal contributions. However, it is not usually possible to distinguish between mantle (low Rb/Sr) and deep crustal sources using Sr 1 values. In contrast, Nd and Pb isotopic data permit such a distinction to be made. The granitoids isotopically analysed for the present study range from calc-alkaline types with mantle or mixed mantle-crust isotopic characteristics (for example, late Archaean orthogneisses from west Greenland) to true granites probably produced solely by anatexis of ancient sialic crust (for example, Badcall Quay red granite, northwest Scotland; Qorqut granite, west Greenland; Mont d’Or granite, Zimbabwe).

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PETROLOGY AND MAGMA GENESIS OF A POST-MIOCENE BASALT FLOW AT SPECIE MESA, SOUTHWESTERN COLORADO

10.1130/abs/2016rm-275859 ◽

2016 ◽

Author(s):

Ethan L. Coppage ◽

◽

David A. Gonzales

Keyword(s):

Basalt Flow ◽

Magma Genesis

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Depletion ages and factors of MORB mantle sources

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2019.115926 ◽

2020 ◽

Vol 530 ◽

pp. 115926 ◽

Cited By ~ 1

Author(s):

Youxue Zhang ◽

Ting Gan

Keyword(s):

Mantle Sources

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Re–Os Pyrite Geochronological Evidence of Three Mineralization Styles within the Jinchang Gold Deposit, Yanji–Dongning Metallogenic Belt, Northeast China

Minerals ◽

10.3390/min8100448 ◽

2018 ◽

Vol 8 (10) ◽

pp. 448 ◽

Cited By ~ 2

Author(s):

Shun-Da Li ◽

Zhi-Gao Wang ◽

Ke-Yong Wang ◽

Wen-Yan Cai ◽

Da-Wei Peng ◽

...

Keyword(s):

Gold Deposit ◽

Northeast China ◽

Gold Mineralization ◽

Metallogenic Belt ◽

Isotopic Analyses ◽

Mantle Sources ◽

Stage 1 ◽

Geochronological Evidence ◽

Gold Bearing

The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources.

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