Pietro Mosca

Metamorphic CO2 Production in Collisional Orogens: Petrological Constraints from Phase Diagram Modeling of Himalayan, Scapolite-bearing, Calc-silicate Rocks in the NKC(F)MAS(T)-HC system

A reliable quantitative estimate of the metamorphic CO2 flux from collisional orogens is fundamental to our understanding of the deep carbon cycle, but it is still far from being constrained. Among major uncertainties are the poor knowledge of the nature of metamorphic CO2-producing processes and the amount of CO2 potentially released through these reactions. Previous studies of metamorphic decarbonation reactions in metacarbonate rocks mainly used simple model reactions between end-members in simplified model systems. However, fully quantitative modelling of calcsilicate rocks requires an investigation of very complex systems with more than six components. Moreover, scapolite solid solution has been rarely included in previous studies, although this mineral is often a major constituent of calc-silicate rocks. This study focuses on (1) the CO2-producing processes occurring in scapolite-bearing calc-silicate rocks and (2) the discussion of a methodological approach suitable to understand and quantify these processes. In this framework, phase relations and devolatilization reactions in the Na2O–K2O–CaO–(FeO)–MgO–Al2O3– SiO2–(TiO2)–H2O–CO2 [NKC(F)MAS(T)-HC] system are considered, with application to high-grade clinopyroxeneþ calciteþK-feldsparþ scapoliteþplagioclaseþ zoisite calc-silicate rocks from the Himalaya. The NKC(F)MAS(T)-HC equilibria involving scapolite and plagioclase solid solutions are investigated using (1) isobaric T–X(CO2) phase diagram sections and pseudosections and (2) mixed-volatile P–T phase diagram projections. This phase diagram approach allowed us to identify scapolite-bearing, CO2-producing, univariant (i.e. isobaric invariant) equilibria that have never been recognized before, and that could not be detected without considering Na–Ca solid solutions in the calculations. It is demonstrated that the investigated calc-silicate rocks behaved as a nearly closed, internally buffered, system during prograde metamorphism and that most of the observed key microstructures correspond to isobaric univariant or invariant assemblages. In such a nearly closed system, the fluid was mostly produced during prograde heating at the isobaric invariant points, where abrupt changes in mineral modes also occurred. The proposed phase diagram approach further allows quantitative estimation of the amount and composition of the fluid produced at such isobaric invariant points. On average, 2 5 mol of CO2 (110 g) per 1000 cm of reacting rock were produced during prograde metamorphism of this calc-silicate rock-type. Because similar scapolitebearing calc-silicate rocks are abundant in the Himalayan orogen, it is suggested that this calc-silicate rock-type might have produced large amounts of CO2-rich fluids during Himalayan metamorphism. A preliminary estimate of these amounts at the scale of the whole orogen suggests a total metamorphic CO2 production of (2–7) 10 mol, corresponding to (1–3) 10 Mt of CO2. Integrated over 20 Myr (i.e. the maximum duration of prograde metamorphism), the VC The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com 53 J O U R N A L O F P E T R O L O G Y Journal of Petrology, 2017, Vol. 58, No. 1, 53–83 doi: 10.1093/petrology/egx005

Metamorphic CO2 Degassing in the Active Himalayan Orogen: Exploring the Influence of Orogenic Activity on the Long-Term Global Climate Changes

A number of studies suggest that mountain ranges have strong impact on the global carbon cycle; metamorphic degassing from active collisional orogens supplies a significant fraction of the global solid-Earth derived CO2 to the atmosphere, thus playing a fundamental role even in today’s Earth carbon cycle. The Himalayan belt, a major collisional orogen still active today, is a likely candidate for the production of a large amount of metamorphic CO2 that may have caused changes in long-term climate of the past, present and near future. Large metamorphic CO2 fluxes are facilitated by rapid prograde metamorphism of big volumes of impure carbonate rocks coupled with facile escape of CO2 to the Earth’s surface. So far, the incomplete knowledge of the nature, magnitude and distribution of the CO2-producing processes hampered a reliable quantitative modeling of metamorphic CO2 fluxes from the Himalayan belt. This study, integrated in the framework of the Ev-K2-CNR SHARE (Stations at High Altitude for Research on the Environment) Project, focuses on the metamorphic decarbonation processes occurring during the Himalayan collision. We hereby present preliminary results focusing on the distribution of different types of metacarbonate rocks in the Eastern Himalaya, their petrographic description and the first reported petrological data about the nature of the CO2-producing reactions in garnet-bearing calc-silicate rocks. These results represent a contribution toward a better understanding of the influence exerted by orogenic processes on climatic changes at global scale.

The Classification Scheme of the Piemonte Geological Map and the OntoGeonous initiative

The OntoGeonous initiative has the goal of modeling a number of interconnected computational ontologies of geological concepts in order to exploit (i) the expressive power of ontological systems to merge several geological concepts (ii) the reasoning capabilities of the ontological systems to check the consistency of the currently existing knowledge stored in the Data Base of the Piemonte Geological Map at 1:250.000 scale and to infer novel knowledge.The prospect application of this initiative is the intelligent data collection and compilation of geological data base and the provision of sound semantic foundations for a modern cartographic project that provides a basis for a synthesis of geological data at the regional scale.

The Monviso massif and the Cottian Alps as symbols of the Alpine chain and geological heritage in Piemonte, Italy.

In order to promote geosite conservation in the project entitled ‘PROactive management of GEOlogical heritage in the PIEMONTE Region’, we propose a comprehensive study involving the Monviso Massif (MM) geothematic area, one of the most outstanding symbols of the Alps and particularly of the Cottian Alps. Specifically, at the MM, the inventory of a number of different geosites whose conservation and development require different geologic and some additional non-geological expertise is considered: (1) some of the best preserved ophiolites in the Alps and the associated Cu–Fe mineralizations; (2) the lithostructural units in the Germanasca Valley; (3) the first primary source of jade in the Alps at the MM and its importance in terms of Neolithic to Bronze Age-polished stone implements; (4) the world-famous minerals such as coesite and giant pyrope, as well as type localities for new minerals (including carlosturanite); (5) the area, now buried under a debris flow, where Hannibal is thought to have regrouped his army while crossing the Alps; and (6) the biodiversity of lichens, microfungi and cyanobacteria colonizing the ophiolites, which can give additional value for the environmental assessment and evaluation of the MM outcrops. Following geodiversity identification, further stages will be devoted to develop appropriate plans for geodiversity conservation in this area.

The Geodatabase of the Piemonte Geological Map: conceptual design for knowledge encoding

The Geodatabase of the Piemonte Geological Map was designed in a way suitable for linking the geological knowledge of the geological domain at hand to more general levels of knowledge represented in some Earth science ontologies and namely in a dedicated ontology (OntoGeonous). The paper describes how the two different knowledge levels are assimilated in the GeoPiemonte informative system, providing relations between the contents of the geodatabase and theencoded concepts of the reference ontologies.

Geodatabase strategy for a digital Geological map of the central-eastern Nepal Himalaya

In this preliminary note, we describe our strategy for collecting, storing and representing new and old geological data acquired in several sectors of the central-eastern Himalaya where, since the 70s, researchers of the CNR- IGG Torino and the Department of Earth Sciences of the University of Torino addressed a significant part of their activity. All the geologic features (including rock samples, petrographic, petrologic and structural observations and measurements) are stored and harmonized in a suitable geodatabase using ArcGIS. Standard criteria are used to describe their typology and quality, facilitating future homogeneous data implementation and a correct data traceability. This geodatabase represents the fundamental starting point for the editing of a digital geological map of the central-eastern Nepal Himalaya.

The Monviso Ophiolite Geopark, a Symbol of the Alpine Chain and Geological Heritage in Piemonte, Italy

The Monviso Ophiolite Geopark (MOG) is one of the strategic geothematic areas chosen to represent the geodiversity of Piemonte within the research project “PROactive management of GEOlogical heritage in the PIEMONTE region”. The MOG is an extraordinary well preserved ophiolite body in the Italian Western Alps. It is one of the best known relics of oceanic crust in the Alps and formed during opening of the Mesozoic western Alpine Tethys and underwent high pressure metamorphism during Alpine subduction. The MOG encompasses the whole lithological spectrum of the Piemonte-Ligurian ophiolites, i.e. metamorphosed peridotite, gabbro, dolerite, basalt, and cover sediments. The MOG gives the almost unique chance for everybody to see and appreciate different portions of the ancient ocean along a mountain trail; from the Po river springs at Pian del Re, to Lago Fiorenza, Lago Lausetto and Lago Superiore, a path rises from 2,000 up to about 2,350 m a.s.l. and shows all different ophiolitic lithologies within few kilometers. The inventory of a number of different geosites at the MOG, whose conservation and development require different expertises, is considered as the first and essential starting point for the geoconservation of geological heritage and geosites.

Preliminary Chemical and Isotopic Characterization of High-Altitude Spring Waters from Eastern Nepal Himalaya

Metamorphic degassing from active collisional orogens supplies a significant fraction of CO2 to the atmosphere, thus playing a fundamental role even in today’s Earth carbon cycle. Appealing clues for a contemporary metamorphic CO2 production in active orogens are represented by the widespread occurrence, along the whole Himalayan belt, of CO2 rich hot-springs mainly localized along major tectonic discontinuities. In contrast to these well-studied hot-springs, almost no chemical and isotopic data are actually available for cold-springs, especially for those located at high-altitude and in remote areas of the Himalayas. In the framework of the Ev-K2-CNR SHARE (Stations at High Altitude for Research on the Environment) Project, we have started a preliminary chemical and isotopic study on high-altitude cold-springs located at different structural levels in the eastern Nepal Himalayas. Chemical and isotopic data obtained from the high-altitude cold-springs are compared with those obtained by previous authors from hot-springs located along the MCT. The isotopic signature of stable isotopes of hydrogen and oxygen could help to identify the waters sources in the investigated Himalayan sectors, to individuate mixing phenomena between waters of different provenience and possible connection with different circulation nets. These first measurements on high-altitude springs from remote areas of eastern Nepal represent a first step towards a better definition of a reliable scenario of water resources availability and will contribute to the understanding of the water cycle in the studied area.

IT applications for sharing geoheritage information: the example of the geological and geomorphological trail in the Monviso massif (NW Italy)

Collection and sharing of geoheritage information are nowadays enhanced by using digital tools and IT (Information Technology) applications that allow homogeneous storing of data, building of sharable databases, and transfer of knowledge between experts and communities. In the frame of the PROGEO-Piemonte project (PROactive management of GEOlogical heritage in the PIEMONTE region), the geological and geomorphological trail in the Monviso Massif (Western Alps) is an example of how IT-applications may support management of geoheritage information. The trail particularly allows walking across the meta-ophiolite succession of an ancient ocean and on glacial landforms. Its realization was supported by different tools that allow (i) capturing of data via GPS handheld mobile device, (ii) managing of field data by means of GIS (Geographic Information Systems) applications, and (iii) virtual visualization of data by means of GIS-based 3D viewer. The different (virtual) views of the geology along the trail can be implemented by adding photos and bookmarks and easily shared through web mapping tools that ensure wide accessibility of geoheritage information.