3-D lithospheric structure and regional/residual Bouguer anomalies in the Arabia-Eurasia collision (Iran)

Abstract

SUMMARY The aim of this work is to propose a first‐order estimate of the crustal and lithospheric mantle geometry of the Arabia–Eurasia collision zone and to separate the measured Bouguer anomaly into its regional and local components. The crustal and lithospheric mantle structure is calculated from the geoid height and elevation data combined with thermal analysis. Our results show that Moho depth varies from ∼42 km at the Mesopotamian–Persian Gulf foreland basin to ∼60 km below the High Zagros. The lithosphere is thicker beneath the foreland basin (∼200 km) and thinner underneath the High Zagros and Central Iran (∼140 km). Most of this lithospheric mantle thinning is accommodated under the Zagros mountain belt coinciding with the suture between two different mantle domains on the Sanandaj–Sirjan Zone. The regional gravity field is obtained by calculating the gravimetric response of the 3‐D crustal and lithospheric mantle structure obtained by combining elevation and geoid data. The calculated regional Bouguer anomaly differs noticeably from those obtained by filtering or just isostatic methods. The residual gravity anomaly, obtained by subtraction of the regional components to the measured field, is analyzed in terms of the dominating upper crustal structures. Deep basins and areas with salt deposits are characterized by negative values (∼−20 mGal), whereas the positive values are related to igneous and ophiolite complexes and shallow basement depths (∼20 mGal).

Lithospheric mantle heterogeneities beneath the Zagros Mountains and the Iranian Plateau: a petrological-geophysical study

“…During the last decade, many efforts have been devoted to unravelling the lithospheric structure and, particularly, in imaging the topography of the crust-mantle boundary (e.g. Paul et al 2006Paul et al , 2010Gök et al 2008;Gritto et al 2008;Sodoudi et al 2009;Manaman et al 2011; see also Jiménez-Munt et al 2012 for a thorough compilation on crustal thickness data).…”

“…Integrated 2-D models combining lithostatic, gravity and thermal equations Jiménez-Munt et al 2012). The colours assigned to the different tectonic units are not related to age or lithology, but are used to highlight their limits.…”

“…(Molinaro et al 2005;Motavalli-Anbaran et al 2011) confirmed a pronounced lithospheric mantle thinning from the Arabian Plate to Central Iran along several lithospheric cross-sections. Jiménez-Munt et al (2012) calculated the lithospheric structure of Iran with the aim of separating the regional/residual gravity anomalies. These authors used a 1-D approach combining geoid height and elevation data and considering the crust as a homogeneous layer with a constant average density and a temperature-dependent lithospheric mantle density.…”

Basin formation by thermal subsidence of accretionary orogens

“…Comparison to the present day lithospheric thickness is not viable because it has been affected by later events, such as the collision between Arabia and Asia in the north and the rifting of the Red Sea in the South West . Published estimates for the lithosphere thickness under Arabia vary markedly between different authors (Hansen et al, 2007;Jimenez-Munt et al, 2012), making it difficult to compare our model results with observations.…”

“…Comparison to the present day lithospheric thickness is not viable because it has been affected by later events, such as the collision between Arabia and Asia in the north and the rifting of the Red Sea in the South West . Published estimates for the lithosphere 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 20 thickness under Arabia vary markedly between different authors (Hansen et al, 2007;Jimenez-Munt et al, 2012), making it difficult to compare our model results with observations. For both the outcrop and the well the proposed subsidence mechanism provides a reasonable fit to the backstripping, but there is a lot more variance from the predicted subsidence curves taken from the modelling than in the other regions studied.…”