Field studies of conductivity anomalies in the lithospheric mantle that may be related to carbon

5/22/2001


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Table of Contents

Field studies of conductivity anomalies in the lithospheric mantle that may be related to carbon

Anomalies ?

Conduction mechanisms likely in the SCLM

EM methods (1)...

EM methods (2)...

Parameter measured: electrical conductivity (1/resistivity) Range...

Fundamenal EM Phenomenon: Skin Depth

MT 1D response: 2-layers

2D Earth response: Graben

Magnetotelluric method: uniqueness theorems

Mantle studies

Lithosphere�.?

Laboratory studies of olivine

Isotropic olivine r-T curve

olivine, opx & cpx

Mantle geotherm

Mantle olivine resistivity

Lithospheric thermal model

Lithospheric resistivity model

Lithospheric resistivity response

Best-fitting smooth model to 1% data

Best-fitting layered model to 1% data

Best-fitting layered models to 1% data

Electronic conduction - sulphides: THO (NACP)

Mantle electrical anisotropy

Mantle electrical anisotropy

SCLM resistivity resolution

Depth to ELAS (electrical asthenosphere)

Variation in depth to ELAS?

Seismic asthenosphere below Baltic Shield

Electrical asthenosphere below NW Baltic Shield

Resistivity of sub-Moho SCLM (depths of 40-100 km)

Western Churchill Province

Western Churchill - MT model

WCH007/8

WCH007/8

WCH007 1D model to AV data

SNORCLE: Slave NORthern Cordilleran Lithospheric Evolution

Lithospheric MT anisotropy

Site 106 decomposed data

Site 106 1D models: both smooth (Occam) & layered (Minim)

Site 106 1D Models with discontinuity in Occam at 36 km

Superior craton

Correlation of EM & seismic anisotropy

Kapuskasing Uplift - anisotropy

Kapuskasing Uplift - anomaly

Alberta: MT site locations

Southern Alberta: MT model

Slave craton

Significant industry interest

Why use electromagnetism?

Slave craton: EM studies

Winter road:

Slave Lakes:

Walmsley Lake TGI project:

Slave location map

MT response comparison

Winter road MT phases

PPT Slide

Slave Lakes prelim. results

Anomalous region

Other anomalous mantle responses

Anomalous ultra-depleted mantle

Griffin�s interpretation

Anomalous geophysical and geochemical regions

PPT Slide

Conduction mechanisms in the mantle

Interpretation in terms of carbon

Observations

Conclusions: Canadian SCLM

Conclusions: general

Author: Alan G Jones

Email: [email protected]

Home Page: http://www.cg.nrcan.gc.ca/staff/jones