The world of fluid inclusions

Fluid inclusions are tiny cavities with minerals that contain a small volume of the fluid percolating in rocks. They are excellent proxies for understanding mineralizing processes, rock alteration, hydrothermalism, diagenesis, metamorphism, palaeo-environments ...

Fluid inclusions form either during growth from that fluid, or during subsequent healing of fratures in the presence of fluid. They are therefore classified as a function of their chronological position relative to the host crystal. Primary inclusions form during crystal growth and therefore register the formation conditions of the host mineral. Secondary inclusions are related to fracturing of the crystal posterior to its formation.

Fluid inclusion studies suppose that three basic postulates are verified :

• the composition of the inclusion has not changed since its formation

• the volume of the inclusions has not changed since its formation

• the microvolume of fluid trapped was homogeneous at the time of inclusion formation

Both two former postulates imply that the bulk density of the fluid has remained constant since the inclusion formation.

General principles of the discipline are summarized in Roedder (2002), including a glossary for common used terms.

Fluid inclusion studies develop during the second part of the XX^th century mainly due to American and Russian scientists, such as E. Roedder and N.P. Ermakov.

• Edwin Roedder's short biography

• Edward Roedder Memorial Library (Virginia Tech geosciences)

• In memory of fluid inclusion research pioneers E. Roedder, N.P. Ermakov, H.C. Sorby and Aly Raichan Beruny

However first observations were carried out since the XIX^th century thanks to H.C. Sorby (1826-1908), a British naturalist. In his paper, Sorby (1858), the founding father of fluid inclusion research marked, particularly the basic postulates.

A complete history of fluid inclusion studies was published by Dubois (2003)^[1] : http://www.annales.org/archives/cofrhigeo/dubois1.html

Whereas publications on fluid inclusions are numerous, books dedicated to this discipline are rare:

Historic reference books:

• Deicha, G. (1955) Les lacunes des cristaux et leurs inclusions fluides. Significations sur la genèse des gîtes minéraux et des roches. Masson, 126 pp.

• Sorby, H.C. (1858) On the microscopic structure of crystals, indicating the origin of minerals and rocks. Quaterly Journal of the Geological Society of London, 14, 453-500

  http://www.biodiversitylibrary.org/item/111684#page/705/mode/1up

• Yermakov, N.P. and collaborators (1965) Research on the nature of mineral-forming solutions with special reference to data from fluid inclusions. Edited by E. Roedder, Pergamon Press, 743 pp. (Translated from Russian)

Reference books:

• Collective work (2001) Fluid Inclusions: Phase Relationships - Methods - Applications. A Special Issue in honour of Jacques Touret. Lithos, 55(1-4): 1-25

• Goldstein, R.H. and Reynolds, T.J., 1994. Systematics of fluid inclusions in diagenetic minerals. SEPM short course, 31. Society for Sedimentary Geology, 199 pp.

• Hurai, V., Huraiova, M., Slobodník, M. and Thomas, R. (2015) Geofluids. Developments in microthermometry, spectroscopy, thermodynamics, and stable isotopes. Elsevier, 489 pp.

• Roedder, E. (1984) Fluid inclusions. Mineralogical Society of America, Reviews in Mineralogy, vol. 12, 646 pp.

• Samson, I., Anderson, A. and Marschall, D. (Editors), Fluid inclusions. Analysis and interpretation. Mineralogical Association of Canada, Vancouver

• Shepherd, T.J., Rankin, A.H. and Alderton, D.H.M., 1985. A practical guide to fluid inclusions studies. Blackie, 239 pp.