Decoupling of Lu-Hf and Sm-Nd Isotopic System in Deep-Seated Xenoliths from the Xuzhou-Suzhou Area, China: Differences in Element Mobility during Metamorphism

The recrystallization of a tholeiitic basalt to garnet granulite and to eclogite has been experimentally examined at temperatures ranging from 800°C up to the solidus of the rock. In addition, the solidus of tholeiitic basalt has been redetermined. The slope of the boundary separating the field of garnet granulite frpm that of basalt is P kb = 0.014 T°C - 5.4 kb. The boundary separating the field of garnet granulite from the field of eclogite has the equation P kb = 0.020 T°C + 4.0 kb. The equation of the newly determined solidus of tholeiitic basalt is T = 6.0 P kb + 1105°C. Curves relating the densities of the mineral assemblages to temperatures and pressures of formation are shown. One relatively abrupt change in density occurs as basalt recrystallizes to garnet granulite, and a second relatively sharp density increase occurs as garnet granulite is recrystallized to eclogite.

Solidus

Recrystallization (geology)

10.1029/gm014p0303

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Research on protolith of eclogite in main hole of Chinese Continental Scientific Drill project and its genetic instructions

The Journal of Geology (2013)

Jian Hu

Eclogite was the most common metamorphic rock in orogenic belt, it contained abundant geodynamic information. According to the contact relationship of country rocks, the eclogite from 0~2 000 m in the main hole of the Chinese Continental Scientific Drill (CCSD) could be classified into three types: symbiotic eclogite gneiss;eclogite adjacent to ultrabasic rocks and symbiotic eclogite ultrabasic rocks. Compared to the geochemical differences with the three types of eclogites, the authors considered that the protoliths of these rocks were probably the basic-untrabasic complex evolved from the single magma chamber by cumulation and fractional crystallization. The main source materials of these protoliths were derived from the enriched mantle by partial melting in subduction zone of oceanic crust downthrusted to the mainland under a back-arc extensional magmatism.

Protolith

Ultramafic rock

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