oa Organic and Rare Earth Elements and Yttrium Geochemistry Related to Structural Features of Maritsa Iztok Basin (Bulgaria)

We present the results of a thorough study on the “odd” numbered symmetric/asymmetric mid-chain n-ketones integrated with REY characteristics in a sequence of carbonaceous mudstone core samples. The amount of nC29-10-one of 100 rel. % at 18.4–18.5 m depth level declined to 21.4 rel. % at 29.3–29.5 m, indicating waxes of various higher plants as a possible progenitor. The values for the nC29-14-one, nC31-16-one, nC33-16-one and nC35-18-one were maximal at 59.5–59.7 m, the depth of elevated maturity. We speculatively related these mid-chain ketones to “pyrolytic” origin.

The REY data normalized to Upper Continental Crust shows smooth patterns of distribution. Weak Ce anomaly infers anoxic to suboxic environment. The distinct positive values (1.11–1.30) for Eu anomaly could be inherited from mafic source rocks, or, be a result of high-temperature fluid injection. The positive values for Gd anomaly (1.05 -1.14) suggest seawater, hydrothermal fluids and other waters influence.

At the present level of knowledge, we suggest that injection of reducing thermal fluids connected with near-surface hydrothermal system and/or tectonic activity could explain “odd” numbered mid-chain ketone formation and REY distribution.