Significance
146
Sm-
142
Nd radioactive systematics can provide constraints on the timing of early differentiation processes on Earth, Moon, and Mars. The uncertainties related to the initial abundance and half-life of the extinct isotope
146
Sm impede the interpretation of the
146
Sm-
142
Nd systematics of planetary materials. The accurate determinations of Sm, Nd, and Mg isotopic compositions of the oldest “andesitic” achondrite Erg Chech 002 (EC 002) define a crystallization age of 1.8 Myr after the formation of the Solar System and provide the most accurate and reliable initial ratio of
146
Sm/
144
Sm for the Solar System at 0.00840
±
0.00032 using a
146
Sm half-life of 103 Ma, making EC 002 an anchor for
146
Sm-
142
Nd systematics for Earth and planetary materials.
Earth’s thermo-tectonic evolution determines the way the planet’s interior and surface interact and shows temporal changes in both trends and periodic rhythms. By sampling the subcontinental lithospheric mantle that represents the interface between the convecting mantle and the crust, carbonatite and kimberlite should be ideal rock types for documenting this evolution. The first-order secular rise of kimberlites over time has been noted by researchers, but there is much debate over how to interpret this trend, and their second-order variability has received less attention. We compiled a comprehensive global carbonatite database and compared it with an existing kimberlite one. We find that the numbers of carbonatites and kimberlites have similar increasing secular trends, with accelerated growth after ca. 1 Ga, and show the same periodic rhythms that have been synchronized to the supercontinent cycle since ca. 2.1 Ga. We link these trends and rhythms to the long-term change of Earth and the supercontinent cycle, both of which have altered the temperature of, and the subduction-recycled volatile flux into, the subcontinental lithosphere. Such consistent records in carbonatite and kimberlite behavior provide critical evidence for the synchronous thermo-tectonic evolution of the entire subcontinental lithosphere.
The Tulaergen magmatic Ni-Cu deposit is related to mafic-ultramafic rocks of the Central Asian Orogenic Belt. The ore-host rocks are lherzolite and websterite and the major ore types are net-textured and sparsely disseminated ores. The disseminated ores host high-Fo (82-85) olivine and hornblende with low-Al contents, high-rare
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