Gresens’ initial ideas about the mobility/immobility of elements and the gains and losses of material in hydrothermal systems, together with the subsequent isocon method proposed by Grant, have led to the development of a considerable number of mass-balance computer programs for application to metasomatic systems (e.g., Leitch and Day, 1990; Potdevin, 1993; Sturm, 2003; Coelho, 2006). Neverthel...

A general problem in compositional data analysis is the unmixing of a composition into a series of pure endmembers. In its most complex version, one does neither know the composition of these endmembers, nor their relative contribution to each observed composition. The problem is particularly cumbersome if the number of endmembers is larger than the number of observed components. This contribut...

Quadrupole mass spectrometry (QMS) is regularly used for online monitoring of gaseous systems. With the advent of miniature QMS, it is possible to apply this capability to the analysis of gas samples extracted from drilling mud during exploration and development of oil and gas fields. QMS analysis can provide rapid compositional data for a range of hydrocarbons, providing early recognition of p...

Factor analysis as a dimension reduction technique is widely used with compositional data. Using the method for raw data or for improperly transformed data will, however, lead to biased results and consequently to misleading interpretations. Although some procedures, suitable for factor analysis with compositional data, were already developed, they require pre-knowledge of variable groups, or a...

Spatial processes with nonstationary and anisotropic covariance structure are often used when modeling, analyzing, predicting complex environmental phenomena. Such may be expressed as ones that have stationary isotropic on a warped spatial domain. However, the warping function is generally difficult to fit not constrained injective, resulting in “space-folding.” Here, we propose modeling an inj...