Anatoly N. Zaitsev, Author at Elements Magazine

Rare Earth Mineralization in Igneous Rocks: Sources and Processes

Deposits of rare earth elements (REEs) in igneous rocks have played an instrumental role in meeting the growing industrial demand for these elements since the 1960s. Among the many different igneous rocks containing appreciable concentrations of REEs, carbonatites and peralkaline silicate rocks are the most important sources of these elements, both historically and for meeting the anticipated growth in REE demand. The contrasting geochemical and mineralogical characteristics of REE mineralization in carbonatites, peralkaline feldspathoid rocks, and peralkaline granites reflect different sources and evolutionary pathways of their parental magmas, as well as differences in the extent of postmagmatic reworking of primary REE minerals by hydrothermal fluids.

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Laetoli: The Oldest Known Hominin Footprints in Volcanic Ash

Into the Rift / Anatoly N. Zaitsev

Hominin footprints are rare in eastern Africa and known from the Laetoli (Tanzania), Ileret (Kenya), and Melka Kunture (Ethiopia) areas. The prints were made by Australopithecus afarensis, Homo erectus,
and Homo heidelbergensis. Their study is an important source of information regarding hominin body size, anatomy, positional behavior, and locomotion biomechanics. The most-known and best-studied examples are the 3.66-Ma Australopithecus afarensis footprint trackways at Laetoli, which represent the oldest known record of hominin bipedalism in Africa. The footprints occur in a volcanic tuff sequence, which was originally deposited as melilite nephelinite ash. Recent excavations show that this valuable paleoanthropological site is slowly disappearing as a result of surface diagenetic processes. Preservation of the footprints is essential and urgently needed.

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Carbonatites: Contrasting, Complex, and Controversial

Carbonatites, Thematic Articles / Vadim (Dima) S. Kamenetsky

Carbonatites are unique, enigmatic, and controversial rocks directly sourced from, or evolved from, mantle melts. Mineral proportions and chemical compositions of carbonatites are highly variable and depend on a wide range of processes: melt generation, liquid immiscibility, fractional crystallization, and post-magmatic alteration. Observations of plutonic carbonatites and their surrounding metasomatic rocks (fenites) suggest that carbonatite intrusions and volcanic rocks do not fully represent the true compositions of the parental carbonatite melts and fluids. Carbonatites are enriched in rare elements, such as niobium and rare earths, and may host deposits of these elements. Carbonatites are also important for understanding the carbon cycle and mantle evolution.

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Author name: Anton R. Chakhmouradian

Rare Earth Mineralization in Igneous Rocks: Sources and Processes

Laetoli: The Oldest Known Hominin Footprints in Volcanic Ash

Carbonatites: Contrasting, Complex, and Controversial

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