Geochemical evidence for “cryptic amphibole fractionation” and lower crust melting for the generation of island arc tholeiitic rocks from northern Fossa Magna, central Japan

Lithos ◽  
2021 ◽  
Vol 386-387 ◽  
pp. 106028
Author(s):  
M. Aizawa ◽  
R. Shinjo ◽  
S. Okamura ◽  
T. Takahashi ◽  
N. Fujibayashi
Keyword(s):  
Lower Crust ◽  
Island Arc ◽  
Central Japan ◽  
Geochemical Evidence ◽  
Northern Fossa Magna ◽  
Amphibole Fractionation

Early sulfide saturation is not detrimental to porphyry Cu-Au formation

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 519-524 ◽  
Author(s):  
Jingguo Du ◽  
Andreas Audétat
Keyword(s):  
Lower Crust ◽  
Silicate Melts ◽  
Mining District ◽  
Sulfide Saturation ◽  
Southeastern China ◽  
Porphyry Cu ◽  
Magmatic Sulfides ◽  
The Common ◽  
Common Association ◽  
Amphibole Fractionation

Abstract Ore-forming magmas are commonly considered to have been unusually metal rich. Because Cu and Au are strongly chalcophile, early sulfide saturation has been regarded as detrimental to porphyry Cu-Au mineralization. Here we demonstrate, based on amphibole-rich cumulate xenoliths and amphibole megacrysts from the Tongling porphyry(-skarn) Cu-Au mining district in southeastern China, that this view is not necessarily correct. Age data combined with petrological and geochemical evidence suggest that the mineralizing magmas at Tongling underwent significant fractional crystallization of amphibole, clinopyroxene, and magmatic sulfides in the middle to lower crust. The fact that the silicate melts nevertheless were able to produce substantial porphyry(-skarn) Cu-Au deposits implies that the formation of metal-rich cumulates at depth was not detrimental to their fertility. On the contrary, the common association of porphyry Cu (Au, Mo) deposits with high-Sr/Y magmas suggests that amphibole fractionation at depth even promotes the mineralization potential, despite the likely loss of metals.

scholarly journals Formation of Distinct Granitic Magma Batches by Partial Melting of Hybrid Lower Crust in the Izu Arc Collision Zone, Central Japan

2007 ◽  
Vol 48 (9) ◽  
pp. 1761-1791 ◽  
Author(s):  
Satoshi Saito ◽  
Makoto Arima ◽  
Takashi Nakajima ◽  
Keiji Misawa ◽  
Jun-Ichi Kimura
Keyword(s):  
Partial Melting ◽  
Lower Crust ◽  
Granitic Magma ◽  
Central Japan ◽  
Collision Zone

Origin of TTG-like rocks from anatexis of ancient lower crust: Geochemical evidence from Neoproterozoic granitoids in South China

Lithos ◽  
2009 ◽  
Vol 113 (3-4) ◽  
pp. 347-368 ◽  
Author(s):  
Shao-Bing Zhang ◽  
Yong-Fei Zheng ◽  
Zi-Fu Zhao ◽  
Yuan-Bao Wu ◽  
Honglin Yuan ◽  
...  
Keyword(s):  
South China ◽  
Lower Crust ◽  
Geochemical Evidence

Chromite in greenstone lavas from the Kanakasu area, Nanjo Massif of the Mesozoic Mino terrane, central Japan

2002 ◽  
Vol 66 (4) ◽  
pp. 575-590 ◽  
Author(s):  
T. Agata ◽  
I. Hattori
Keyword(s):  
Chemical Composition ◽  
Oceanic Island ◽  
Island Arc ◽  
Basalt Magma ◽  
Central Japan ◽  
Compositional Zoning ◽  
Oceanic Ridge ◽  
Host Magma ◽  
Alkalic Basalt ◽  
Alkalic Basalts

AbstractChromite occurs together with olivine as phenocrysts in basalts of the Kanakasu greenstone body. Chromite forms inclusions within olivine phenocrysts; it also constitutes discrete phenocrystic grains scattered in the groundmass. The Cr and Ni contents of chromite-bearing olivine basalts are unusually high relative to the MgO content. This is probably due to the presence of phenocrystic chromite and olivine. The mineralogy suggests that the groundmass of the basalts is hawaiitic in composition. Chromite, generally, is unlikely to crystallize from differentiated magma such as hawaiite melt. The chromite and associated olivine phenocrysts are probably xenocrysts. Discrete chromite commonly shows compositional zoning that resulted from reaction with host magma; some chromite evidently changed in composition. Chromite embedded in olivine was shielded from reaction with host magma, and has preserved the original chemical composition. The composition of embedded chromite ranges: Mg/(Mg+Fe2+) 0.37–0.58, Cr/(Cr+Al) 0.47–0.64, Fe3+ 0.16–0.47 p.f.u., and Ti 0.034–0.13 p.f.u. The relatively high Ti and Al contents suggest that chromite crystallized from an alkalic basalt magma. The Cr/(Cr+Al) ratio is relatively high when compared to those of chromite in mid-oceanic ridge and island-arc alkalic basalts; the Kanakasu embedded chromite is chemically identical to chromite from Hawaiian alkalic basalts. The Kanakasu chromite was probably formed in an intraplate oceanic island.

The Lead Isotope Characteristics and Tracing Significance of Ore Metallogenic Material in the Geza Arc,Yunnan

2014 ◽  
Vol 1073-1076 ◽  
pp. 2054-2057
Author(s):  
Xue Long Liu ◽  
Na Zhang ◽  
Jian Kang
Keyword(s):  
Lower Crust ◽  
Lead Isotope ◽  
Development Stage ◽  
Island Arc ◽  
Geochemical Characteristics ◽  
Pb Isotopes ◽  
Isotopic Data ◽  
Porphyry Deposits ◽  
Intrusive Rocks ◽  
Polymetallic Ore

Geza arc is the important parts of Yidun island arc in southwest of Sanjiang tectonic magmatic belts, it located in the southern tip of the Yidun island arc, which is a newly discovered copper polymetallic ore concentration area in the recently years in China. Based on the development stage of island arc orogenic, the distribution of intrusive rocks, composition, geochemical characteristics, Geza island arc granits belt can be divided into three belts. Geza island arc several typical porphyry deposits Pb isotopic data show that Pb206/Pb204 17.680~19.165, Pb207/Pb204 15.453~15.773,change in scope, Pb208/Pb204 37.730~39.654. Most of samples are normal lead, Pb isotopes focused on the side of orogenic evolution line and the lower crust range,with the characteristics of crust-mantle mixed source.

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