This is the first attempt to provide a general mineralogical and geochemical survey of natural Ca 2 SiO 4 -bearing combustion metamorphic (CM) rocks produced by annealing and decarbonation of bioproductive Maastrichtian oil shales in the Hatrurim Basin (Negev Desert, Israel). We present a synthesis of data collected for fifteen years on thirty nine minerals existing as fairly large grains suitable for analytical examination. The Hatrurim Ca 2 SiO 4 -bearing CM rocks, which are natural analogs of industrial cement clinker, have been studied comprehensively, with a focus on several key issues: major-and trace-element compositions of the rocks and their sedimentary precursors; mineral chemistry of rock-forming phases; accessory mineralogy; incorporation of heavy metals and other trace elements into different phases of clinker-like natural assemblages; role of trace elements in stabilization/destabilization of Ca 2 SiO 4 polymorphic modifications; mineralogical diversity of Ca 2 SiO 4 -bearing CM rocks and trace element partitioning during high-temperature-low-pressure anhydrous sintering. The reported results have implications for mineral formation and element partitioning during high-temperature-low-pressure combustion metamorphism of trace element-loaded bituminous marine chalky sediments ("oil shales") as well as for the joint effect of multiple elements on the properties and hydration behavior of crystalline phases in industrial cement clinkers.

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Minerals of the Zn-Cd-S-Se system that formed by moderately reduced ~800–850 °C combustion metamorphic (CM) alteration of marly sediments were found in marbles from central Jordan. Their precursor sediments contain Se- and Ni-enriched authigenic pyrite and ZnS modifications with high Cd enrichment (up to ~10 wt%) and elevated concentrations of Cu, Sb, Ag, Mo, and Pb. The marbles are composed of calcite, carbonate-fluorapatite, spurrite, and brownmillerite and characterized by high P, Zn, Cd, U, and elevated Se, Ni, V, and Mo contents. Main accessories are either Zn-bearing oxides or sphalerite, greenockite, and Ca-Fe-Ni-Cu-O-S-Se oxychalcogenides. CM alteration lead to compositional homogenization of metamorphic sphalerite, for which trace-element suites become less diverse than in the authigenic ZnS. The CM sphalerites contain up to ~14 wt% Cd and ~6.7 wt% Se but are poor in Fe (means 1.4–2.2 wt%), and bear 100–250 ppm Co, Ni, and Hg. Sphalerite (Zn,Cd,Fe)(S,O,Se)cub is a homogeneous solid solution with a unit cell smaller than in ZnScub as a result of S2− → O2− substitution (a = 5.40852(12) Å, V = 158.211(6) Å3). The amount of lattice-bound oxygen in the CM sphalerite is within the range for synthetic ZnS1−xOx crystals (0 < x ≤ 0.05) growing at 900 °C.

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—Marly limestone, marble, and gabbro–dolerite samples from the Kochumdek contact aureole are studied in order to estimate to which degree the spurrite–merwinite (T = 750–900 °C) metamorphism at the site was isochemical. The 3 m wide zoned Kochumdek aureole is located at the contact between the Early Triassic trap intrusion of the Kuzmovka complex (vβT1kz) and the overlying Llandovery marine marly limestones (Sıln) of the lower Kochumdek subformation in the right side of the Kochumdek River (tributary of the Podkamennaya Tunguska, East Siberia). The Kochumdek rocks are remarkable by the lack of prominent skarn or vein mineralization in marbles and autometasomatism in gabbro. The samples have been analyzed for major, chalcophile, rare-earth, and high-field strength elements. The Kochumdek marbles and marly limestones share similarity in major-element patterns that record mixing of fine siliciclastic material with biogenic and chemogenic CaCO3 components. The major-element chemistry of marly limestones has been controlled by the compositions of fine clastic material transported from the provenance (Trans-Angara part of the Yenisei Ridge) and by the deposition environment of the early Silurian marine basin. The contents of Cu, Ni, Co, V, Mo, Se, Cr, and U in marly limestones and marbles correspond to marine sediments deposited in a low-productive oxigenated environment. The Ni/Co, V/Cr, Cu/Zn, V/(V+Ni), and U/Th ratios in spurrite marbles at the intrusive contact remain within typical limestone ranges but differ from those in gabbro, which have higher V and Cu enrichment and moderate contents of Zn, Ni, and Co. Marly limestones and spurrite marbles show identical REE+Y patterns and average ΣREE contents. The major- and trace-element similarity between marbles and the protolith limestones, along with the absence of gabbro geochemical signatures in the metamorphic rocks, indicate that the thermal metamorphism was nearly isochemical. The reactions occurred without any large-scale transport of major and trace elements across the sill/sediment boundary. The conditions were unfavorable for metasomatic alteration due to low fluid saturation of the Kochumdek intrusion and its structural setting, as well as to the lithological, mechanical, and thermal properties of the sediments.