Marble: a metamorphic rock composed of >50% carbonate minerals (calcite, aragonite, or dolomite).

Pure marble contains >95% carbonate minerals.

Carbonate-silicate rock: Metamorphic rock mainly composed of silicate minerals and containing 5-50% carbonate minerals.

Calc-silicate rock: Metamorphic rock primarily composed of Ca-rich silicates and <5% of carbonate minerals.

Ca-silicate minerals include: diopside, grossular, Ca-amphiboles, vesuvianite, epidote, wollastonite, etc.

Skarn: a contact metamorphosed and silica metasomatized carbonate rock containing calc-silicate minerals, such as grossular, epidote, tremolite, vesuvianite, etc. Tactite is a synonym.

A portion of the Alta aureole in Little Cottonwood Canyon, SE of Salt Lake City, UT, where talc, tremolite, forsterite, and periclase isograds were mapped in metacarbonates by Moore and Kerrick (1976) Amer. J. Sci., 276, 502-524.

Chemographics in the CaO-MgO-SiO₂ -CO₂ -H₂O system, projected from CO₂ and H₂O. The green shaded areas represent the common composition range of limestones and dolostones. Due to the solvus between calcite and dolomite, both minerals can coexist in carbonate rocks. The dark red left half of the triangle is the area of interest for metacarbonates. Carbonated ultramafics occupy the right half of the triangle.

The sequence of CaO-MgO-SiO₂-H₂O-CO₂ compatibility diagrams for metamorphosed siliceous carbonates (shaded half) along an open-system (vertical) path up metamorphic grade for X_CO2 < 0.63 in Figure 29-3. The dashed isograd requires that tremolite is more abundant than either calcite or quartz, which is rare in siliceous carbonates.

Type 3: T_max at X_CO2 determined by the stoichiometric ratio of CO₂/H₂O produced

Ca₂Mg₅Si₈O₂₂(OH)₂ + 3 CaCO₃ + 2 SiO₂ = 5 CaMgSi₂O₆ + 3 CO₂ + H₂O

Schematic T-XCO₂ phase diagram illustrating the general shapes of the five types of reactions involving CO₂ and H₂O fluids. After Greenwood (1967). 

In P. H. Abelson (ed.), Researches in Geochemistry. John Wiley. New York. V. 2, 542-567. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

T-X_CO2 phase diagram for siliceous carbonates at P = 0.1 GPa. Calculated using the program TWQ of Berman (1988, 1990, 1991). The green area is the field in which tremolite is stable, the reddish area is the field in which dolomite + diopside is stable, and the blue area is for dolomite + talc. Compatibility diagrams, similar to those in Figure 29-4, show the mineral assemblages in each field.

Metamorphic zones developed in regionally metamorphosed dolomitic rocks of the Lepontine Alps, along the Swiss-Italian border. After Trommsdorff (1966) Schweiz. Mineral. Petrogr. Mitt., 46, 431-460 and (1972) Schweiz. Mineral. Petrogr. Mitt., 52, 567-571.

T-X_CO2 phase diagram for siliceous carbonates at P = 0.5 GPa, calculated using the program TWQ of Berman (1988, 1990, 1991). The light-shaded area is the field in which tremolite is stable, the darker shaded areas are the fields in which talc or diopside are stable.

Isograds mapped in the field. Note that isograd (5) crosses the others in a manner similar to that in part (a). This behavior is attributed to infiltration of H₂O from the syn-metamorphic pluton in the area, creating a gradient in X_H2O across the area at a high angle to the regional temperature gradient, equivalent to the T-X diagram.

T-X_H2O diagram illustrating the shapes and relative locations of the reactions for the isograds mapped in the Whetstone Lake area. Reactions 1, 2, and 4 are dehydration reactions and reaction 3 is the Ky = Sil transition, all in metapelites. Reaction 5 is a dehydration-decarbonation in calcic rocks with a temperature maximum at X_H2O = 0.25.

Schematic T-X_CO2 diagram illustrating the characteristic shape of typical dehydration reactions, such as those that generate orthopyroxene from hornblende or biotite. Notice that the amphibolite facies to granulite facies can be accomplished by either an increase in temperature or infiltration of CO₂ at a constant temperature.

Petrogenetic grid for water-saturated ultramafic rocks in the system CaO-MgO-SiO₂-H₂O produced using the TWQ software of Berman (1988, 1990, 1991). The green arrow represents a typical medium P/T metamorphic field gradient. The dark blue area represents the stability range of anthophyllite in "normal" ultramafic compositions. The lighter blue area represents the overall stability range of anthophyllite, including more siliceous ultramafic rocks.

Chemographics of ultramafic rocks in the CMS-H system (projected from H₂O) showing the stable mineral assemblages (in the presence of excess H₂O) and changes in topology due to reactions along the medium P/T metamorphic field gradient illustrated in Figure 29-10. The star represents the composition of a typical mantle lherzolite. Dashed reactions represent those that do not occur in typical ultramafic rocks, but rather in unusually SiO₂-rich or SiO₂-poor varieties.

Simplified T-X_CO2 phase diagram for the system CaO-MgO-SiO₂-H₂O-CO₂ at 0.5 GPa, calculated using the program TWQ of Berman (1988, 1990, 1991). The diagram focuses on ultramafic-carbonate rocks and omits reactions involving quartz. The shaded fields represent the stability ranges of serpentine-antigorite (purple), anthophyllite in typical low-SiO₂ ultramafics (blue), and tremolite in low-SiO₂ ultramafics (green).