1 / 13

Missing Pb, High 3 He/ 4 He, Ancient Sulfides and Continental Formation

Missing Pb, High 3 He/ 4 He, Ancient Sulfides and Continental Formation . Shichun Huang Harvard University U Nevada, Las Vegas Cin -Ty A. Lee Rice University Qing-Zhu Yin University of California, Davis. Goldschmidt Conference | Sacramento, CA | June 13, 2014 .

nell
Download Presentation

Missing Pb, High 3 He/ 4 He, Ancient Sulfides and Continental Formation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Missing Pb, High 3He/4He, Ancient Sulfides and Continental Formation Shichun Huang Harvard University U Nevada, Las Vegas Cin-Ty A. Lee Rice University Qing-Zhu Yin University of California, Davis Goldschmidt Conference | Sacramento, CA | June 13, 2014

  2. Copper deficit in continental crust 10 1 V Sc Cu Conc./PM 0.1 0.01 Sequestration via sulfides-bearing cumulates? MORB Bulk Continental Crust (BCC) Upper Continental Crust (UCC) Lower Continental Crust (LCC) Lee et al. 2012

  3. Continental arcs FeOT Mt Hb TH Gt BCC Ol, Cpx CA Na2O + K2O MgO Kfs wt. %

  4. +1.3 A Cordilleran plutons ΔFMQ +1.3 +1.2 Cordilleran arc pyroxenites +1.2 +1.1 C +1.0 +1 Sf Cu (ppm) +0.9 +0.7 0 0 MORB cpx 100 mm 100 mm MgO (wt. %) B Pyroxenites +1.3 +1.2 +1.1 +1.0 +0.9 Sf Cu (ppm) +0.7 MORB & Prim. Mantle 0 cpx Mg# = Mg/(Mg+Fe)T Lee et al. 2012; Science

  5. Cumulates contain the missing Cu 2 1 3 4 Can re-melting Cu-rich cumulates give rise to Cu-rich magmas? Lee et al. 2012; Science

  6. Composition of the sulfide-bearing cumulates S-bearing, Cu-rich Pb-bearing NO URANIUM ---possible low U/Pb reservoir? Lee et al. 2012 (Science) Lee et al. 2007 (EPSL)

  7. What about 4He? • noble gas solubility in a variety of liquids can potentially be described byatomic radius and surface tension(e.g., Uhlig, 1937; Blander et al., 1958; Lux, 1987) • at 1300 oC, DHesf/sil = 0.3 or higher • He has a finite solubility in sulfide liquids g: macroscopic surface tension r: atomic radius of the noble gas Low (U+Th)/He Primordial 3He/4He Huang et al. 2014; Scientific Reports

  8. (U+Th)/Pb and (U+Th)/He evolution of mantle • Pb and He isotopic composition of mantle is frozen in when sulfide-bearing cumulates are formed Huang et al. 2014

  9. UnradiogenicPb correlates with unradiogenicHe: primitive or frozen signatures of ancient crust formation? e143Nd 207Pb/204Pb 206Pb/204Pb Jackson et al. 2010; Jackson and Carlson, 2011

  10. Pb-He Isotopic Correlation of Oceanic Basalts • Negative 206Pb/204Pb – 3He/4He trend • Controlled by ancient sulfides Huang et al. 2014; Scientific Reports

  11. Observations: He-Pb Isotopic Correlation • Spatial correlation of He-Pb isotopes coincident with ancient lithosphere Graham et al.2009 And data downloaded from GeoRoc database

  12. He Isotopes and Continental Growth? • Parman suggested that He is more compatible during melting than U. But this does not explain Pb. • Better interpretation? • He and Pb explained by sulfide • segregation during crust formation Parman (2007)

  13. Cumulates from crustal differentiation -unradiogenicPb and He -sulfide-bearing -ore metal bearing Huang et al. 2014; Scientific Reports Lee et al. 2012; Science

More Related