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Drilling the continental crust into the Moho transition zone (Ivrea-Verbano zone, Italy)

Europe, Italy, Ivrea, Southern Alps

revised workshop-proposal: ICDP-2016/17
for the funding-period starting 2016-01-15
by Othmar Müntener, Mattia Pistone, Luca Ziberna, Alberto Zanetti, György Hetényi
Abstract
We propose an ICDP-sponsored international workshop to develop a strategic proposal for planning and preparing a full drilling of the continental lower crust into the Moho transition zone in the Ivrea-Verbano Zone (IVZ) in the Southern Alps in Italy. The geophysical data show that the IVZ is unique in that the Moho transition zone can be followed from the Po Plain at ~30 km depth to about 15 km in the IVZ where it reaches at a dip of more than 45°. The IVZ is one of the classic cross sections of the lower continental crust. Recent discoveries illustrate that the IVZ is a precious archive of continental magmatism documenting lower crustal processes of magma emplacement, crystallisation, and crustal assimilation, and the development of near surface magmatism including evidence of super-eruptions during a protracted time in the Permian. Drilling the IVZ would provide a unique and continuous set of geochemical, structural, and geophysical data on the nature of the continental lower crust and the crust-mantle transition, the construction and organisation of a deep crustal magmatic system, and the physical conditions (i.e. magma fluxes, magma/country rock rheology, density, seismic velocities). Drilling will additionally investigate heat production and distribution of heat producing elements across a continuous, finely banded sequence of lower crustal rocks, major pre-Alpine and Alpine crustal shear zones, present-day alteration processes, fluid compositions, and its relationships to the major orogenic fault structure of the Alps, the Insubric Line. From a logistic point of view, the IVZ offers good accessibility for drilling facilities. We propose a workshop in the area of Verbania (Italy) in the heart of the IVZ, where the strategy of drilling in the IVZ will be discussed and a drilling proposal will be initiated and planned to be submitted in 2018.
Scientific Objectives
  • The scientific objective can be summarised along two major lines of research goals (1) Composition and variability of the continental lower crust and characterisation of the continental crust-mantle transition, through:
  • i) sampling a continuous section by up to 5 km deep drill holes or by several offset shallower boreholes (1 to 2km in length) of both continental lower crust and into the crust-mantle transition zone – combining these offset drill cores would be an alternative and ‘cheaper’ solution to obtain a ±continuous section of up to 10 km, and ii) conducting direct measurements of the physical properties of the rocks in situ, such as heat production and flow variation with depth, rock density, elastic wave velocity, and bulk fluid contents (2) Geological and seismic structure of the lithosphere, through determining:
  • i) the geometry of mantle-derived ultramafic bodies and their transition zones to lower crustal rocks,
  • ii) the attitude at depth of the IVZ compositional layering and foliation and the sharpness of this gradation,
  • iii) the presence and geometry of Alpine thrusts and pre-Alpine faults within the IVZ,
  • iv) the variation of the Alpine metamorphic overprint with depth, and calibration of various thermochronometers v) the hydration level of crustal rocks with depth.
Keywords
Continental crust, Europe, ICDP-2016/17, Italy, IVREA, Moho transition zone, Rock physics, Seismic structure, Southern alps
Location
Europe, Italy, Ivrea, Southern Alps: 45.93333, 8.53333

© ICDP, the International Continental Scientific Drilling Program, 1996-2020

www.icdp-online.org