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The integrated approach combining kinematic and structuralparagenetic field tectonophysics techniques allows us to construct a continuous time scan of the stressstrain state (SSS) and deformation modes (DM) from sediment lithification to the final orogenic process for the studied areas. Definitions of the continuous sequence of SSS and DM provide for control of the known geodynamic reconstructions and adjustment of geodynamic models. An example is the tectonophysical study of the Alpine structural stage of the Western Mountainous Crimea (WMC) and the PreCambrian complexes of the Ukrainian Shield (USh). Data from WMC allow us to make adjustments to the geodynamic model of the Mountainous Crimea. In particular, tra jectories of the principal normal stresses (Fig. 4 and 5), both for shifts and shear faults with reverse components/ normal faults, suggest the reverse nature of movements of the Eastern and Western Black Sea microplates with their overall pushing onto the Crimean peninsula in the southeast, south and southwest (Fig. 7). In the Precambrian USh complexes (Fig. 8), 13 stages of regional deformation are revealed between ≥2.7 and 1.6 billion years ago. Until the turn of 2.05-2.10 billion years, the region was subject to transtension and transpression, as the Western (gneissgranulite) and Eastern (granitegreenstone) Archean microplates of USh moved to separate from each other in the NeoArchean and then diverged and converged in the Paleoproterozoic (movements at a sharp angle). It is assumed that in the Archean the Western and Eastern microplates were separated by the oceanic or suboceanic lithosphere (Fig. 12, 13). During the period of 2.3-2.4 billion years, the plates fully converged creating a zone of collision. It may be suggested that a possible mechanism for the oceanic window closeup was underthrusting of the upper suboceanic lithosphere layers beneath the crustmantle plates on gently sloping breakup surfaces (nonsubduction option), and one of them is Moho. Spreading of the Western and Eastern microplates of USh began at the turn of 2.05-2.10 billion years, as evidenced by the available tectonophysical data on fields of latitudinal extension of the crust. During spreading 2.1-2.05 billion years ago, emanations and solutions were able to ascend into the upper crust and thus stimulate palingenesis (Novoukrainsky and Kiro vogradsky granites), and during repeated spreading 1.75 billion years ago, magma of the basic and acid composition (Pluto gabbroanorthosite and rapakivi) intruded into the upper crust. The spreading zone coincided with the former collisional su ture and became the site wherein the interregional KhersonSmolensk suture was formed; it stretches submeridionally across the East European platform.

At low temperatures (<750 °C at moderate to high crustal pressures), the production of suffi cient melt to reach the melt connectivity transition (~7 vol%), enabling melt drainage, requires an infl ux of aqueous fl uid along structurally controlled pathways or recycling of fl uid via migration of melt and exsolution during crystallization. At higher temperatures, melting occurs by fl uid-absent reactions, particularly hydrate-breakdown reactions involving micas and/or amphibole in the presence of quartz and feldspar. These reactions produce 20-70 vol%, melt according to protolith composition, at temperatures up to 1000 °C. Calculated phase diagrams for pelite are used to illustrate the mineralogical controls on melt production and the consequences of different clockwise pressure-temperature (P-T) paths on melt composition. Preservation of peritectic minerals in residual granulites requires that most of the melt produced was extracted, implying a fl ux of melt through the suprasolidus crust, although some may be trapped during transport, as recorded by composite migmatitegranite complexes. Peritectic minerals may be entrained during melt drainage, consistent with observations from leucosomes in migmatites, and dissolution of these minerals during ascent may be important in the evolution of some crustal magmas. Since siliceous melt wets grains, suprasolidus crust may become porous at only a few volume % melt, as evidenced by microstructures in residual migmatites in which quartz or feldspar pseudomorphs form after melt fi lms and pockets. With increasing melt volume and decreasing effective pressure, assuming the residue is able to deform and compact, the source becomes permeable at the melt connectivity transition. At this threshold, a change from distributed shear-enhanced compaction to localized dilatant shear failure enables melt segregation. The result is a highly permeable vein network that allows transfer of melt to ascent conduits at the initiation of a melt-extraction event. Melt is drained from the anatectic zone via several extraction events, consistent with evidence for incremental construction of plutons from multiple batches of magma. Buoyancy-driven magma ascent occurs via dikes in fractures or via high-permeability zones controlled by tectonic fabrics; the way in which these features relate to compaction and the generation of porosity waves is discussed. Emplacement of laccoliths (horizontal tabular intrusions) and wedge-shaped plutons occurs around the ductile-to-brittle transition zone, whereas steep tabular sheeted and blobby plutons represent back freezing of melt in the ascent conduit or lateral expansion localized by instabilities in the magma-wallrock system, respectively.

An extensive, thick MgO-rich primary crust underlain by highly residual mantle must have formed during the Archaean as a consequence of higher ambient mantle potential temperatures 1. However, the preserved volume of this crust is low suggesting much of it was recycled 2. Further, the tonalite-trondhjemite-granodiorites that dominate exposed Archaean crust cannot have been generated directly from MgO-rich primary crust since a hydrated low-MgO basalt source is required 3. Here we show that the thermodynamically stable mineral assemblages expected at the base of fully hydrated and anhydrous MgO-rich crust 45 km thick make it denser than the complementary underlying residual mantle. We use 2-D geodynamic models to explore the fate of this gravitationally unstable crust. Our results demonstrate that magmatically-overthickened MgO-rich crust, whether fully hydrated or anhydrous, could have delaminated by Rayleigh-Taylor instabilities for mantle potential temperatures > 1500-1550 °C, depending on rheology. The dripping instabilities generate return flow of asthenospheric mantle that melts adiabatically producing additional primary crust. Melting of overthickened and dripping MgO-rich crust and intracrustal fractionation of primary magmas both may produce the hydrated nature geoscience SUPPLEMENTARY INFORMATION

Ages retrieved from accessory minerals in high-grade metamorphic rocks place important constraints on the timing of events and the rates of tectonometamorphic processes operating in the deep crust. In suprasolidus rocks, the dissolution and growth of zircon and monazite are strongly dependent on the P-T conditions of metamorphism and the chemistry and quantity of anatectic melt present. Along a clockwise P-T path, prograde heating above the solidus leads to episodic melt loss and changes in melt chemistry that have important implications for the dissolution and growth of zircon and monazite. In this study, phase equilibria modelling of open-system melting is coupled with experimental data on zircon and monazite solubility to evaluate the stability of these minerals at suprasolidus conditions along several schematic clockwise P-T paths. In migmatite melanosomes and residual granulites, some zircon is expected to survive heating to peak temperature and subsequent isothermal decompression, whereas monazite may be completely consumed, consistent with the observation that inherited cores are less common in monazite than in zircon. After decompression, during cooling to the solidus, new zircon and monazite growth from melt trapped along grain boundaries in melanosomes and residual granulites is expected to be limited. By contrast, leucosomes in migmatites and anatectic granites are predicted to contain mostly newly formed zircon and monazite with minimal inherited components, unless significant entrainment of these minerals from the source occurs. The preservation of cores inside newly formed zircon, as observed in many anatectic granites, demonstrates that segregation, ascent and emplacement is commonly fast enough to limit dissolution of these inherited grains.