Jean-François Moyen

Université Jean Monnet · Département de Géologie

Archean rocks of the tonalite-trondhjemite-granodiorite (TTG) suite are dominant constituents of Earth’s earliest preserved silicic crust, while conversely rare in Phanerozoic continental crust. Their formation represents the first critical step towards the construction and preservation of continents. Formation of most TTG magmas involved partial m...

La chaîne varisque en France 2 traite de l’histoire géologique et de l’évolution des idées concernant la chaîne varisque en France.Cet ouvrage propose une analyse des évènements magmatiques, métamorphiques et tectoniques tardifs ainsi que des archives sédimentaires, documentant ainsi le démantèlement de la chaîne varisque au Carbonifère supérieur.L...

The ancient cores of modern continents, cratons, are the oldest blocks of “stable” lithosphere on Earth. Their long-term survival relies on the resistance of their underlying thick, strong, and buoyant mantle keels to subsequent recycling. However, the effect of substantial geographical variations in keel thickness on the post-assembly behaviour an...

Secular trends in plutonic whole-rock geochemistry pose critical, although non-unique, constraints to early Earth tectonics. Here, we present a large whole-rock geochemical (879 collated samples) dataset for granitoids from the Pilbara Craton, Western Australia, applying it to test the link between secular trends and proposed tectonic mechanisms. W...

Stable Ca isotopes are an increasingly useful tool for understanding the sources and processes leading to the formation of magmatic rocks, yet Ca isotope fractionation during genesis of silicic continental crust is still poorly understood. Here, we present Ca, Sr, and Nd isotope, as well as major- and trace-element whole-rock geochemical data for A...

Recent advances in thermodynamic modelling now allow phase equilibrium studies of partial melting in mafic and ultramafic sources under upper mantle conditions. This potentially offers several advantages over experimental investigations, including the fact that capsule-sample interactions are avoided, there is no uncertainty over the volatile conte...

The South Indian Dharwar Craton assembled during the late-Archaean (ca. 2.5 Ga). This event was associated with intense granite genesis and emplacement. Based on petrography and geochemistry, 4 main types of late Archaean granitoids were distinguished: (1) Anatectic granites (and diatexites), formed by partial melting of TTG gneisses; (2) Classical...

Thermo-chemical modelling and chemical data suggest that the genesis of arc melts commonly involves re-melting of older intrusions, triggered by the injection of mantle-derived melts, followed by magma mixing. Remelting and mixing may lead to complex zircon populations, which can be used to gain insights into the conditions of mixing. This paper in...

How the geological record of cratons reconciles with the tectonic environments in which they formed has remained debated. We use 2D Cartesian geometry numerical models of mantle convection varying temperatures from present day to Archaean‐inferred values, to address the formation of cratons, accounting for melt depletion‐dependent rheological stiff...

In the original plate-tectonic centric framework for Earth evolution as proposed in the 1960s, the term ‘subduction’ was initially applied to the down thrusting of oceanic lithosphere below a continental or oceanic upper plate, delineated by a Wadati-Benioff zone of earthquake foci. Over time, the use of the term has broadened and its meaning weake...

Magmatic hydrothermal mineral deposits axiomatically frame the hosting pluton and the given tectonic setting in which they are inserted. Unsurprisingly, pre-Cambrian porphyry deposits are different than Phanerozoic examples, as collisional or post-collisional deposits are different than arc-related mineralizing systems. As such, this contribution a...

The oldest geological materials on Earth are Hadean (>4 Ga) detrital zircon grains. Their chemistry and apparently low Ti-in-zircon temperatures (≤700 °C) are considered to be inconsistent with crystallization in a magma of the tonalite-trondhjemite-granodiorite (TTG) suite, although these are the dominant Archean (4.0–2.5 Ga) silicic rocks. Using...

Granitoids are a major component of the continental crust. They play a pivotal role in its evolution, either by adding new material (continental growth), or by reworking older continental crust. These two roles correspond to two main ways of forming granitic magmas, either by partial melting of pre-existing crustal rocks yielding granitic melts dir...

Granitic melts may form either directly, by melting of pre-existing crustal rocks, or by fractionation of mafic to intermediate magmas, typically mantle-derived. Each model is applicable to different portions of the Earth at different times. Whenever there is an important flux of mafic magmas from the mantle, differentiation of basaltic magmas domi...

Le style tectonique de la Terre Archéenne reste, malgré des décennies de recherche, un sujet de controverse. Dans les dernières décades, le débat s’est polarisé entre des modèles actualistes (tectonique des plaques), et des modèles non-actualistes très variés, qui n’ont en commun que leur opposition à une tectonique des plaques de type moderne. Bie...

Anastomosing branching and wavy laminae in quartz-rich sandstones of the 3.22 Ga Moodies Group in the Barberton Greenstone Belt (BGB), South Africa, have been extensively described as fossilized microbial mats developed in terrestrial to marine transitional environments. Petrological and geochemical characteristics of a ~ 350 m thick Moodies succes...

The origin and classification of granites and related rocks are the two fundamental aspects of igneous petrology. This volume is based on the 9th Hutton symposium that was held at Nanjing in China in 2019. It focuses on micro- to macro-scale aspects that are temporally and spatially linked to sources and processes of granitic magmatism. These aspec...

The thermal state of the crust controls its rheology and is therefore an important variable in understanding Archean tectonic processes. Thermochronology is a useful tool to track the long-term thermal evolution of the crust, and U-Pb in apatite, with an effective closing temperature for volume diffusion of Pb of ca. 400–550 °C, is useful in constr...

We describe the multi-scale distribution of K, Th and U in the ca. 3.1 Ga Heerenveen batholith of the Barberton Granite-Greenstone Terrain. Data were obtained with a combination of tools, including a portable gamma-ray spectrometer from the scale of the whole batholith to the scale of outcrops, and autoradiography for the thin section scale. U is c...

The aim of this paper is to determine the composition and age of high-temperature (HT) hydrothermal fluids in Closepet granites (Dharwar craton, India). The magmatic origin of the Neoarchaean Closepet batholith has been recognized and dated many times, whereas a HT fluid system, strong evidence for which has been partly investigated, has never been...

Zircon U-Pb geochronology is routinely performed to unravel the timing and duration of melting events within the continental crust. A comprehensive understanding of the zircon behavior during anatexis is therefore paramount to accurately assess the impact of crustal melting on orogenic processes. We report on an anatectic system from the southern p...

We generate theoretical curves for zircon growth during cooling of tonalitic and A-type granitic magmas and compare these with empirical Ti-in-zircon populations from the Paleoarchean Pilbara Craton, Australia, Mesoarchean Akia Terrane, Greenland, and the Mesoproterozoic Musgrave Province, Australia. Our models predict variable zircon growth rates...

The stabilization of Archaean cratons is accompanied by a transition from juvenile granitic magmatism, to reworking of the pre-existing crust. In this work, we examine the granitoids associated to the ca. 3.1 Ga stabilization of the Kaapvaal Craton of Southern Africa, and investigate the origin and petrogenesis of the granodiorite-monzogranite-syen...

S-type granites correspond to reworking of pre-existing continental material and form by partial melting of (meta)sediments. Early-to-mid Archean S-type granites are rare and are more frequently found, usually as relatively small intrusions, during the Neoarchean and the Archean-Proterozoic transition. In the context of Archean geology, their pauci...

Granitoids form the dominant component of Archean cratons. They are generated by partial melting of diverse crustal and mantle sources and subsequent differentiation of the primary magmas, and formed through a variety of geodynamic processes. Granitoids, therefore, are important archives for early Earth lithospheric evolution. Peninsular India is c...

We present here a tectonic-geodynamic model for the generation and flow of partially molten rocks and magmatism during the Variscan orogenic evolution from the Silurian to the late Carboniferous based on a synthesis of geological data from the French Massif Central. Eclogite facies metamorphism of mafic and ultramafic rocks records the subduction o...

The Moodies Group, the uppermost unit in the Barberton Greenstone Belt (BGB) in South Africa, is a ~3.7-km-thick coarse clastic succession accumulated on terrestrial-to-shallow marine settings at around 3.22 Ga. The multiple sulfur isotopic composition of pyrite of Moodies intervals was newly obtained to examine the influence of these depositional...

Whole-rock geochemistry represents a powerful tool in deciphering petrogenesis of magmatic suites, including granitoids, that can be used to formulate and test hypotheses qualitatively and often also quantitatively. Typically, it can rule out impossible/improbable scenarios and further constrain the process inferred on geological and petrological g...

Granites (s.l.) come in many types and flavours, defining distinct magmatic series/suites/types. A good classification not only gives generally accepted and understandable names to similar rocks, but also links the bulk chemical composition to the stoichiometry of the constituent minerals and, potentially, also to the likely source, magmatic evolut...

Granitoids of the tonalite–trondhjemite–granodiorite (TTG) series dominate Earth’s earliest continental crust. The geochemical diversity of TTGs is ascribed to several possible geodynamic settings of magma formation, from low-pressure differentiation of oceanic plateaus to high-pressure melting of mafic crust at convergent plate margins. These inte...

Granites are igneous rocks largely dominated by quartz and feldspar, and a wide range of accessory minerals. However, their apparently simple mineralogy hides a large diversity of rocks and a great complexity of igneous processes. Granites can be formed by fractionation of mantle-derived basaltic magma, melting of various components of the continen...

More than 15 years have passed since the Geochemical Data Toolkit (GCDkit) was released at the Goldschmidt Conference in Kurashiki [1]. This freeware, written in the potent R language [2; http://www.r-project.org] evolved into an established standard for plotting and recalculation of whole-rock geochemical data from magmatic rocks [3]. It can be do...

The ability of Rcrust software to conduct path-dependent phase equilibrium modelling with automated changing bulk compositions allows for a phase equilibrium approach to investigate an array of source controls for their effect on the bulk compositions of melts produced by sequential melting events. The following source controls of the rock system a...

This paper describes the petrology, geochemistry and petrogenesis of Archean granitoids. Archean granites define a continuum of compositions between several end members: (i) magmas that originated by partial melting of a range of crustal sources, from amphibolites to metasediments (‘C-type’ granitoids); and (ii) magmas that formed by partial meltin...

The origin of large I-type batholiths remains a disputed topic. One model states that I-type granites form by partial melting of older crustal lithologies (amphibolites or intermediate igneous rocks). In another view, granites are trapped rhyolitic liquids occurring at the end of fractionation trends defining a basalt–andesite–dacite–rhyolite serie...

Modern quantitative phase equilibria modelling allows the calculation of the stable phase assemblage of a rock system given its pressure, temperature and bulk composition. A new software tool (Rcrust) has been developed that allows the modelling of points in pressure–temperature–bulk composition space in which bulk compositional changes can be pass...

Combining U–Pb and Lu-Hf isotopic data of detrital zircon grains has proven a powerful tool to unravel the provenance of sediments and address continental crust evolution. In this study, we explore the origin of thick siliciclastic metasedimentary units from the high-grade internal domains of the Variscan belt of Europe and examine their significan...

The chemical composition of different rocks as well as volatile-bearing and volatile-free minerals has been used to assess the presence of fluids in the Closepet batholith and to estimate the intensity of the fluid–rock interactions. The data were processed using polytopic vector analysis (PVA). Additional data include measurements of water content...

Modern quantitative phase equilibria modelling allows the calculation of the stable phase assemblage of a rock system given its pressure, temperature and bulk composition. A new software tool (Rcrust) has been developed that allows the modelling of points in pressure–temperature–bulk composition space in which bulk compositional changes can be pass...

Anatectic magmas form plutons or accumulate in the core of anatectic domes. Both scenarios have distinct implications on the behaviour of the continental crust during orogenic evolution from collision to collapse. Considering a stepwise extraction of melt, we simulate the evolution of anatectic melt and of solid residues produced in the crust from...

Partial melting is a key orogenic process in controlling the rheology of evolving thickened crust. Consequently, understanding the location of the solidus in pressure-temperature (P-T) space is critical. Investigations of the onset of anatexis in rocks are limited as, using conventional modelling or experimental approaches, it is impossible to adeq...

This work examines the global distribution of Archaean and modern igneous rock's compositions, without relying on preconceptions about the link between rock compositions and tectonic sites (in contrast with “geotectonic” diagrams). Rather, Archaean and modern geochemical patterns are interpreted and compared in terms of source and melting condition...

Geodynamics of crustal growth and evolution consist in one of the thorniest questions of the early Earth. In order to solve it, Archean cratons are intensively studied through geophysical, geochemical and geochronological investigations. However, timing and mechanisms leading to accretion and stabilization of crustal blocks are still under question...

Phase equilibria modelling studies investigating the onset of anatexis in rocks are limited by the assumption of a fixed H2O content in the bulk composition. This limitation is in conflict with the fact that the water content of fluid-absent subsolidus rocks change as a function of pressure and temperature. Rcrust [1] allows phase equilibrium model...

The East Massif Central (EMC), France, is part of the internal zone of the Variscan belt where late Carboniferous crustal melting and orogenic collapse have largely obliterated the pre- to early-Variscan geological record. Nevertheless, parts of this history can be reconstructed by using in-situ U-Th-Pb-Lu-Hf isotopic data of texturally well-define...

The late stages of the Variscan orogeny are characterized by middle to lower crustal melting and intrusion of voluminous granitoids throughout the belt, which makes it akin to “hot” orogens. These processes resulted in the development of large granite–migmatite complexes, the largest of which being the 305–300-Ma-old Velay dome in the eastern Frenc...

In phase equilibrium modelling it is often impossible to constrain the H2O content of the modelled composition precisely. Best practice for choosing a realistic H2O content for the rock composition, is usually to construct an isobaric temperature-XH2O pseudosection and use mineral assemblage and mineral composition information to constrain the most...

As modelling is conducted with the specific purpose of understanding a series of igneous rocks, it is important to keep it firmly rooted in geological truth. This chapter discusses some of the limitations of the modelling exercise: some processes that may seem feasible from a geological point of view are physically unrealistic, for instance. We als...

This chapter shows a worked example, modelling the crustal anatexis to form a migmatitic complex. Starting with geological and petrological data, we describe the main geochemical features of the lavas and model their evolution. In this environment, the melts are not well extracted from their solid residue. They are poorly homogenised and their comp...

The best proofs for operation of open-system processes remain radiogenic isotope ratios, which are generally not fractionated during closed-system processes such as melting or crystallization. The magmas formed should preserve the isotopic characteristics of their source. In other words, the radiogenic isotope data are totally transparent to mechan...

This chapter contains five solved problems on forward modelling of the behaviour of trace elements using R (see Chaps. 11 and 13 for principles). They include theoretical treatment of batch and fractional crystallization equations, development of REE during tonalite magma fractionation, partial melting of primitive mantle or depleted mantle reservo...

By combining the mass balance (Chap. 6) and partition coefficient (Chap. 10) concepts, it is possible to derive a range of laws that relate the trace-element composition of a melt to that of its source, the nature and proportion of solid phases (cumulate or restite), etc. Various laws are written to account for different situations (melting, crysta...

This chapter contains two solved problems on reverse modelling of the behaviour of trace elements using R (see Chap. 12 for principles). One concerns fractionation of tonalitic magma (given the compositions of primitive and fractionated melt and partition coefficients of the principal mineral phases). The other is a reverse problem of garnet lherzo...

The aim of this chapter is to explain basic numerical (R-language) approaches in interpreting radiogenic isotope data in igneous geochemistry, with particular emphasis on Sr–Nd–Hf–Os isotopic systems. The text is concerned with calculation of initial ratios, ages ε and γ values, single- and two-stage model ages and fitting of isochrons. Practical e...

This rather short chapter explains fundamentals of fitting binary mixing hyperbolae to real data arrays (e.g., in 87Sr/86Sr vs. 143Nd/144Nd plots). This is done by the least-square method, and the outputs are asymptotes with curvature. The second part of the text presents reverse solution of the AFC as described by Powell (1984), using the slope of...

This chapter contains four solved problems on reverse modelling of the behaviour of major elements using R (see Chap. 7 for principles). These include reverse modelling of fractional crystallization, partial melting of a paragneiss (yielding granitic magma) and calculation of a general “norm” given the composition of a bulk rock and its constituent...

In this chapter, plain R recipes are presented to produce the most common graphs used in igneous geochemistry, such as binary plots (simple and multiple, e.g. Harker plots), ternary plots or spiderplots. Practical exercises illustrating the general principles are also included. Special attention is given to dealing with spurious correlations in bin...

This chapter presents several less known (or newly designed) types of geochemical plots that are implemented in GCDkit. It does not aim at being systematic and comprehensive; instead it focuses on arguably the most useful or interesting among them that could be suitable for common applications in igneous geochemistry. These include log–log binary p...

This chapter presents numerical tools to “revert” the mass-balance relation (of Chap. 6), and explain the composition of a given igneous rock in terms of mixing between different components (solids or liquids). The proportions of each component can be constrained if their compositions are known. Thus it is possible to gain information on, e.g. the...

Earth's continental crust is dominantly made of buoyant, felsic igneous material (granitoids), that were ultimately extracted from the mantle as a result of Earth's differentiation. Since felsic melts are not in chemical equilibrium with the mantle, they can originate either from melting of older crustal lithologies, or from differentiation of a pr...

Earth's continental crust is stabilised by crustal differentiation that is driven by partial melting and melt loss: Magmas segregate from their residuum and migrate into the upper crust, leaving the deep crust refractory. Thus, compositional change is an integral part of the metamorphic evolution of anatectic granulites. Current thermodynamic model...

The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth’s geodynamic processes. The detrital zircon record within the continental crust, as well as the isotopic composition of this crust, indicates that the amount of juvenile felsic material decreased with time and that in geologically recent times, th...

Although modelling is all about understanding a suite of rocks and relating observations to variables in a model (Chap. 22), some useful numerical tricks are important to keep in mind. Most relate to the fact that the composition of a rock can be seen as a vector in an n-dimension space (n being the number of elements in consideration). Some of the...

This chapter shows how information can be gleaned from various sources to con-strain the parameters needed to build a full model. Some of the parameters come from observations of the petrology or the geochemical patterns of the rocks stud-ied. In other cases, information must be sought from the literature. The remaining parameters can be calculated...

This chapter presents a range of geological and petrological evidence that can be used to decide on the process shaping the geochemistry of a rock suite. In turn, we discuss the evidence for crystallization, melting and mixing (and assimilation), and we show which of the laws discussed in Chaps. 6 and 11 are more appropriate for each situation.

This chapter contains five solved exercises on forward modelling of the behaviour of major elements using R (see Chap. 6 for principles). These include: fractional crystallization of a single mineral and of a more complex cumulate assemblage, partial melting of a mantle peridotite and origin of basaltic magmas, and calculation of a bulk rock compos...

The concept of partition coefficient becomes useless for elements that form a significant (stoichiometric) portion of a mineral. Such is the case for many accessory minerals including zircon (controlling Zr) and monazite (controlling LREE and Th). In this case, a more appropriate concept is that of solubility (of the accessory mineral). This chapte...

This chapter contains three solved problems on forward modelling of the behaviour of isotopes using R (see Chap. 16 for principles). The exercises deal with plotting mixing hyperbolae for a single isotope system (in the Sr vs. 87Sr/86Sr and 1/Sr vs. 87Sr/86Sr coordinates) and an Sr–Nd isotope pair (in the 87Sr/86Sr vs. 143Nd/144Nd plot). The last e...

Some numerical tools can be used to further constrain the processes shaping the geochemistry of a rock suite (see Chap. 20). The numerical form of the different laws established before (especially for trace elements, Chap. 11) is such that, in well-chosen diagrams, different processes will generate immediately distinguishable patterns. We discuss s...