GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 3.3 717 Tab. 1 - Fit parameters of the linear relationships of Fig. 1. ID description slope [10 -6 W/m 3 ] intercept [10 -3 W/m 2 ] a 40 km crust, true relationship 1.13 15.82 b 50 km crust, true relationship 1.13 12.29 c using Q(SFC) for 40 and 50 km crust, apparent rel. 0.79 29.39 d using Q(CMB) in the transition zone, apparent rel. 0.59 38.42 decreases for a thicker crust, while the slope is the same, which is consistent with their identical composition (for values see Tab. 1). The apparent relationships we obtain by fitting the surface heat flow values at the two markers (undisturbed by the transition, line c ) or along the transition zone (line d ) underestimate the crustal production and overestimate . We also test the effect of inversion to an apparent gravimetric CMB of the gravity anomaly of a sill-like disturbing body (80x2 km), more radioactive (+2 µW/m 3 ) and buoyant in respect to the reference crust (-200 kg/m 3 ). Using the apparent CMB for a thermal forward modelling skews the surface heat flow prediction up to 4 mW/m 2 residuals: a small quantity compared with the uncertainties involved, but enough to significantly alter the fit of a linear relationship (errors of up to -0,76 µW/m 3 in average heat production and +30 mW/m 2 in ). Acknowledgements Work by author AP is being supported by a grant under the European Social Fund HEaD 2014/2020, through resources of Region Friuli Venezia Giulia in the form of a PhD fellowship at the University of Trieste (FSE-EUS/4). References Braitenberg, C., Wienecke, S., Ebbing, J., Born, W., Redfield, T. (2007). Joint Gravity and Isostatic Analysis for Basement Studies –������ ����� ANovel Tool. EGM 2007 International Workshop, Innovation in EM, Grav and Mag Methods: A New Perspective for Exploration, 16–18. Chapman, D. S. (1986). Thermal gradients in the continental crust. Geological Society, London, Special Publications , 24 (1), 63–70. DOI:10.1144/GSL.SP.1986.024.01.07 Huang, Y., Chubakov, V., Mantovani, F., Rudnick, R. L., McDonough, W. F. (2013). A reference Earth model for the heat-producing elements and associated geoneutrino flux. Geochemistry, Geophysics, Geosystems , 14 (6), 2003– 2029. DOI:10.1002/ggge.20129 Freymark, J., Sippel, J., Scheck-Wenderoth, M., Bär, K., Stiller, M., Kracht, M., &Fritsche, J. G. (2015). Heterogeneous Crystalline Crust Controls the Shallow Thermal Field - ACase Study of Hessen (Germany). Energy Procedia , 76 , 331–340. DOI:10.1016 /j.eg ypro.2015.07.837 Fullea, J., Afonso, J. C., Connolly, J. A. D., Fernàndez, M., Garcia-Castellanos, D., Zeyen, H. (2009). ��������� �� LitMod3D: An interactive 3-D software to model the thermal, compositional, density, seismological, and rheological structure of the lithosphere and sublithospheric upper mantle. Geochemistry, Geophysics, Geosystems , 10 (8), 1–21. DOI:10.1029/2009GC002391 Jaupart, C. (1983). Horizontal heat transfer due to radioactivity contrasts: causes and consequences of the linear heat flow relation. Geophysical Journal International , 75 (2), 411–435. DOI:10.1111/j.1365-246X.1983.tb01934.x Jaupart, C., Mareschal, J.-C. (2011). Heat Generation and Transport in the Earth . Cambridge University Press. ISBN:9781139493628 Jokinen, J., Kukkonen, I. T. (1999). Random modelling of the lithospheric thermal regime: Forward simulations applied in uncertainty analysis. Tectonophysics , 306 (3–4), 277–292. DOI:10.1016/S0040-1951(99)00061-X Lachenbruch, A. H. (1970). Crustal temperature and heat production: Implications of the linear heat-flow relation. Journal of Geophysical Research , 75 (17), 3291. DOI:10.1029/JB075i017p03291 Lee, W. H. K., Uyeda, S. (1965). Review of heat flow data. In Terrestrial heat flow (Vol. 8, pp. 87–190). American Geophysical Union. DOI:10.1029/GM008p0087 Nielsen, S. B. (1987). Steady state heat flow in a randommedium and the linear heat flow-heat production relationship. Geophysical Research Letters , 14 (3), 318–321. DOI:10.1029/GL014i003p00318 Pastorutti, A., Braitenberg, C. (2017). Geothermal estimates from GOCE data alone: assessment of feasibility and first results. In EGU General Assembly Conference Abstracts (Vol. 19, EGU2017-15930-2). Rudnick, R. L., McDonough, W. F., O��������� �� �� ������� ������� ���������� ��������� ��� ����������� �� ’Connell, R. J. (1998). Thermal structure, thickness and composition of continental lithosphere. Chemical Geology , 145 (3–4), 395–411. DOI:10.1016/S0009-2541(97)00151-4