the embarrassing details about geochemical mass balance models for calculating mantle composition n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition PowerPoint Presentation
Download Presentation
The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition

Loading in 2 Seconds...

play fullscreen
1 / 5

The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition - PowerPoint PPT Presentation


  • 124 Views
  • Uploaded on

The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition. (they are trivially simple, but they do give some interesting results if you ask the right questions). The Physical Principal – Conservation of Mass. Melt or Crust. Bulk Silicate Earth

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition' - fran


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
the embarrassing details about geochemical mass balance models for calculating mantle composition

The Embarrassing Details about Geochemical Mass Balance Models for Calculating Mantle Composition

(they are trivially simple, but they do give some interesting results if you ask the right questions)

the physical principal conservation of mass
The Physical Principal – Conservation of Mass

Melt or Crust

Bulk Silicate Earth

(the hypothetical homogeneous composition of the solid silicate Earth after core formation, but before any other differentiation process)

[a] (mg/g)

MassBSE

Mass of “a” = MassBSE x [a]BSE

Residue or Depleted Mantle

Mass of element “a” = MassDM x [a]DM + MassC x [a]C + Mass(BSE-DM-C) x [a]BSE

the physical principal conservation of mass1
The Physical Principal – Conservation of Mass

Reservoir A (atmosphere)

Reservoir CC (Cont. Crust)

Bulk Earth

(the hypothetical average homogeneous composition of the Earth)

[a] (mg/g)

MassBE

Mass of “a” = MassBE x [a]BE

Reservoir OC (Oceanic Crust)

Reservoir DM (Depleted Mantle)

Reservoir BSE

Reservoir Core

Reservoir Moon

Mass of “a” = MassA x [a]A + MassCC x [a]CC + MassOC x [a]OC + MassDM x [a]DM + MassCore x [a]Core + MassBSEx [a]BSE + MassMoon x [a]Moon + etc., etc. etc.

the necessary inputs
The Necessary Inputs
  • Mass and composition of (n-1) reservoirs
  • If interested only in composition, then all that matters is the mass balance, not the rates of exchange (unless you are interested in how a given reservoir changed in composition with time)
  • If interested in the radiogenic isotope compositions (e.g. 87Sr/86Sr), then how and when the various reservoirs formed is critical
some examples of the questions you can ask
Some Examples of The Questions You Can Ask
  • If the BSE differentiates into continental crust and depleted mantle, given the mass and composition of the continental crust, what portion of the mantle can be as depleted as the source of MORB? How does this change with different estimates of the BSE composition? Do you get the same answer when you use a highly incompatible element (e.g. Ba) and a moderately incompatible element (e.g. Sm)?
  • If the continental crust has the average composition given in the program, could it be 5 times its current size at the same composition? If not, why not?
  • How much Nb must be in the core to explain the non-chondritic Nb/U ratio of the mantle?
  • How does the composition of the EER vary as a function of its size?
  • Can the Moon be the EER? What would its composition be? The mass of the Moon is approximately twice the mass of the continental crust.
  • The mass of the atmosphere is 5 x 1021g of which 0.93% is argon, and most of that argon is 40Ar produced by the decay of 40K over Earth history. 40K decays to 40Ar and 40Ca with a decay constant of 5.54 x 10-10 yr-1, with 11 % of the decay going to 40Ar. The BSE has 240 ppm of K, only 0.012% currently of which is 40K. If all of the 40Ar in the atmosphere came from 40K decay, how much 40Ar remains in the mantle? If all the radiogenic 40Ar is in the atmosphere, what is the K content of the BSE?