Origin and significance of magmatic inclusions

This paper reviews work on magmatic (particularly silicate-melt) inclusions in terrestrial and extraterrestrial samples and evaluates its significance. For ordinary inclusions, formed during normal magmatic differentiation by crystal fractionation, this review details the trapping mechanisms, the three main changes that may occur within inclusions after they have been trapped (separation of an immiscible fluid phase, crystallization, and leakage), and the five main types of useful data available from such inclusions (temperature of trapping, temperatures and sequence of phase changes during cooling, constraints on maximum and minimum cooling rates, bulk composition and the liquid line of descent, and the volatile content). Other inclusions in magmatic rocks are trapped and have their compositions determined by a variety of types of fluid immiscibility. Although several types of inclusions, particularly in the lunar samples, are still inexplicable, magmatic inclusions have yielded much useful data and show great promise for the future. Some of these data are unavailable from any other source.Cet article est une revue critique des travaux sur les inclusions magmatiques (de bain silicaté en particulier) dans les échantillons terrestres et extraterrestres. Pour les inclusions ordinaires, formées durant la différenciation magmatique normale par cristallisation fractionnée cette revue détaille les mécanismes de piégeage, les trois changements principaux qui peuvent se produire dans les inclusions après ce piégeage (séparation d'une phase fluide immiscible, cristallisation et fuite) et les cinq principaux types d'informations qu'elles peuvent apporter (température de piégeage, températures et séquence des changements de phases durant le refroidissement, contraintes sur les vitesses maximales et minimales de refroidissement, composition globale, cheminement du liquide et teneur en fluides). D'autres types d'inclusions sont piégés dans les roches magmatiques et leur composition est déterminée par diverses immiscibilités entre fluides. Quoique plusieurs types d'inclusions, particulièrement dans les échantillons lunaires, soient encore non expliqués, les inclusions magmatiques ont apporté de nombreuses informations utiles et sont susceptibles d'en apporter encore beaucoup d'autres. Quelques-unes de ces informations ne peuvent provenir d'aucune autre source.Roedder Edwin. Origin and significance of magmatic inclusions. In: Bulletin de Minéralogie, volume 102, 5-6, 1979. Minéraux et minerais

Significance of Ca-Al-rich silicate melt inclusions in olivine crystals from the Murchison type II carbonaceous chondrite

The Murchison chondrite meteorite has been studied extensively. It consists of olivine˗pyroxene aggregates and isolated crystals, which formed at high temperatures, in a hydrous, carbonaceous matrix, mainly layer lattice silicates, which formed at low temperatures. The olivine crystals contain Ca-Al-silicate melt inclusions. Several workers (Fuchs, Grossman, Olsen, and others) have proposed that the melt inclusions represent globules of melt formed by direct (metastable ?) condensation from the solar nebula ; they further have proposed that the globules were subsequently enclosed, while still viscous, by olivine crystals growing from a vapor phase (mainly hydrogen) at about 1 170°C and ≤ 10⁻³ atm. My studies of the inclusions indicate that this theory is incorrect, and that the inclusions and the olivine formed from a gas-bearing melt. The evidence is as follows : 1) glass (now phyllosilicates) coats the outer faces of some sharply euhedral olivines ; 2) pseudosecondary planes of troilite, glass and « vapor » inclusions are found in olivine ; and 3) several ~ 300 µm iron-rich olivines were found that have thick, almost inclusion-free rims and sharply defined, more magnesian cores that are densely and uniformly crowded (~ 5 x 10¹⁰ cm⁻³) with < 1 µm, mainly « vapor »-rich inclusions. These observations, and the lines of evidence presented by other workers, are most compatible with a relatively high temperature, two-stage formation of the olivine crystals from a gas-bearing, olivine-rich silicate melt containing some Ca and Al, rather than from a vapor phase.La chondrite de Murchison est constituée d'agrégats et de cristaux isolés d'olivine et de pyroxène formés à haute température, inclus dans une matrice hydratée et carbonée formée surtout de phyllosilicates de basse température. Les cristaux d'olivine contiennent des inclusions vitreuses de silicates alumino-calciques. Plusieurs auteurs (Fuchs, Grossman, Olsen, etc...) ont proposé que ces inclusions représentent des globules fondus formés par condensation directe (métastable ?) de la nébuleuse solaire ; les gouttes seraient ensuite englobées encore visqueuses, par des cristaux d'olivine croissant à partir d'une phase vapeur (surtout hydrogénée) vers 1 170°C et sous pression de ≤ 10⁻³ atm. Les observations suivantes suggèrent une cristallisation de l'olivine à partir d'un bain fondu contenant des gaz. 1) Présence de verre (maintenant phyllosilicates) couvrant les faces externes de cristaux euhédraux. 2) Présence de plans pseudo-secondaires riches en inclusions de troïlite, verre, « vapeur », dans l'olivine. 3) Présence de cristaux d'olivine riche en fer de 300 µm ayant une bordure nette dépourvue d'inclusions et un cœur plus magnésien uniformément bourré (~ 5 x 10¹⁰ cm⁻³) de fines (< 1 µm) inclusions « gazeuses ». Ces observations, jointes à d'autres, sont compatibles avec une histoire de cristallisation en deux étapes, à température relativement élevée, l'olivine croissant d'un bain silicaté plutôt que d'une phase vapeur.Roedder Edwin. Significance of Ca-Al-rich silicate melt inclusions in olivine crystals from the Murchison type II carbonaceous chondrite. In: Bulletin de Minéralogie, volume 104, 4, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Deuxième partie : inclusions magmatiques / silicates / gemmes / « open session »

United States Geological Survey Report TEI-703

The following report discusses the problems of injection and the possibility of chemical reactions occurring upon contact between earth materials and typical high-level acid aluminum nitrate wastes, along with proposed methods of disposal of such wastes by injection into deep-lying, brine-saturated permeable beds (salaquifers)

Evidence for an unsaturated-zone origin of secondary minerals in Yucca Mountain, Nevada

The unsaturated zone (UZ) in Miocene-age welded tuffs at Yucca Mountain, Nevada, is under consideration as a potential site for the construction of a high-level radioactive waste repository. Secondary calcite and silica minerals deposited on fractures and in cavities in the UZ tuffs are texturally, isotopically, and geochemically consistent with UZ deposition from meteoric water infiltrating at the surface and percolating through the UZ along fractures. Nonetheless, two-phase fluid inclusions with small and consistent vapor to liquid (V:L) ratios that yield consistent temperatures within samples and which range from about 35 to about 80 C between samples have led some to attribute these deposits to formation from upwelling hydrothermal waters. Geochronologic studies have shown that calcite and silica minerals began forming at least 10 Ma and continued to form into the Holocene. If their deposition were really from upwelling water flooding the UZ, it would draw into question the suitability of the site as a waste repository

Fluid inclusions in quartz from oceanic hydrothermal specimens and the Bingham, Utah porphyry-Cu deposit: a study with PIXE and SXRF

International audienceIndividual natural fluid inclusions in quartz were selected for non-destructive microprobe analysis by synchrotron X-ray fluorescence (SXRF) and proton-induced X-ray emission (PIXE) in order to compare and contrast the compositions of porphyry-type ore forming brines and two types of ocean crustal brines. The inclusions contained brines with high salt concentrations (typically 20–40 wt.% total), and one or more daughter crystals. The X-ray and proton beams produced detectable characteristic X-rays for many elements and allowed the quantification of concentrations for many elements with atomic number Z>14.Fluid inclusions associated with the core of the Bingham, UT, porphyry-Cu(Mo) deposit contain NaCl brines that also contain (element, typical range in ppm): K, 12,000–100,000; Ca, ≤17,000; Mn, ≤8000; Fe, ≤120,000; Cu, ≤8000; Zn, ≤5000; Br, ≤2000. These values are in good agreement with published estimates, and results from SXRF and PIXE experiments are generally consistent. The Bingham fluid compositions closely resemble brines from the porphyry-Mo(Cu) deposit at Questa, NM.Inclusions from two suites of oceanic plutonic rock samples gave PIXE results consistent with published SXRF analyses from other inclusions in the same samples. New inclusion analyses from the Mathematician Ridge locality indicate the NaCl brines also contain, on average (element, ppm): K, 3500; Ca, 35,000; Mn, 4900; Cu, 400; Zn, 200; Br, 1000. New inclusion analyses from the Oceanographer Transform locality indicate NaCl brines that also contain, on average: K, 37,000; Ca, 35,000; Mn, 10,000; Cu, ≤400; Zn, 2200; Br, 1000. These values are calculated on the assumption that Fe in the inclusions is 50,000 ppm. Compared to continental ore forming brines, the oceanic brines have higher Ca and lower K and Cu concentrations