Abstract In NE China, voluminous granitoids were emplaced in late Paleozoic and Mesozoic times. We report here Sr–Nd–O isotopic and elemental abundance data for two highly evolved granitic plutons, Woduhe and Baerzhe, from the Great Xing'an Mountains. They show a rather “juvenile” Sr–Nd isotopic signature and a spectacular tetrad effect in their REE distribution patterns as well as non-CHARAC (charge-and-radius-controlled) trace element behavior. The emplacement ages are constrained at 130±4 Ma for the Woduhe and 122±5 Ma for the Baerzhe granites by Rb–Sr and Sm–Nd isotope analyses. Both granites are also characterized by low but imprecise initial 87Sr/86Sr ratios of about 0.703. The Nd–Sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust. This is largely compatible with the general scenario for much of the Phanerozoic granitoids emplaced in the Central Asian Orogenic Belt. The parental magmas for both the Woduhe and Baerzhe granites have undergone extensive magmatic differentiation, during which intense interaction of the residual melts with aqueous hydrothermal fluids (probably rich in F and Cl) resulted in the non-CHARAC trace element behavior and the tetrad effect of REE distribution. Both the Woduhe and Baerzhe granites show the characteristic trace element patterns of rare-metal granites, but their absolute abundances differ by as much as two orders of magnitude. The oxygen isotope compositions of the two granites have been severely disturbed. Significant 18O depletion in feldspar, but not so much in quartz, suggests that the hydrothermal alteration took place in a temperature condition of 300–500 °C. This subsolidus hydrothermal alteration is decoupled from the late-stage magma–fluid interaction at higher temperatures. Despite the two distinct and intense events of “water–rock” interaction, the Rb–Sr and Sm–Nd geochronological systems seem to have maintained closed, hence, suggesting that the two events occurred shortly after the plutonic emplacements.

Highly evolved juvenile granites with tetrad ree patterns: the woduhe and baerzhe granites from the great xing'an mountains in ne china

Mineralogical, geochemical and Sr-Nd isotopes characteristics of fluorite-bearing granites in the Northern Arabian-Nubian Shield, Egypt: Constraints on petrogenesis and evolution of their associated rare metal mineralization

A-type granitoid in Hasansalaran complex, northwestern Iran: Evidence for extensional tectonic regime in northern Gondwana in the Late Paleozoic

We present the first chemical age determination of monazite from a geochemically-specialized rare metal granite of the Central Eastern Desert (CED), Egypt. The Abu Diab composite A-type granite of the CED divides into three co-magmatic phases: two mica granite (TG), garnet-bearing muscovite granite (GMG), and muscovite granite (MG). The GMG granitic phase is a typical example of a rare metal, volatile-rich aqueous silicate magma. Its zircon has extremely high U-concentration (up to 45,000 ppm) and intense metamictization, resulting in significant radiogenic Pb-loss, as well as common Pb contamination, along fractures and other imperfections. Laser ablation (LA-ICP-MS) zircon U-Pb results yield imprecise to meaningless dates. On the other hand, the GMG exhibits two texturally and chemically distinct varieties of monazite, pristine (Mnz1) and altered (Mnz2), that yield similar electron microprobe (EMP) chemical ages of 587 ± 8 Ma (2σ) for Mnz1 and 587 ± 9 Ma (2σ) for Mnz2. These ages, combined with the inferred alteration temperature (T > 400 °C), indicate monazite alteration/replacement occurred during or soon after crystallization of the pluton, in response to expelled magmatic-hydrothermal fluids inferred to be F-rich, late-staged deuteric fluids. The alteration and elemental substitution of zircon and monazite reflect coupled dissolution-recrystallization processes during late-staged deuteric alteration when zircon and thorite were relatively vulnerable to post-magmatic hydrothermal effects because of their extremely metamict state. The ca. 587 Ma age is typical of A-type granite intrusion across the CED and the post-collisional stage of the Arabian Nubian Shield (ANS; 610 – 560 Ma), and is within analytical error of associated magmatic thorite (592 ± 8 Ma). These two ages agree with the timing of rare metal-rich intrusions (0.6−0.4 Ga) related to the Pan-African orogeny. Future research using the monazite chronometer may better constrain the timing of rare metal granitic magmatism of the ANS.

Combined zircon U-Pb dating and chemical Th─U─total Pb chronology of monazite and thorite, Abu Diab A-type granite, Central Eastern Desert of Egypt: Constraints on the timing and magmatic-hydrothermal evolution of rare metal granitic magmatism in the Arabian Nubian Shield

Composition and origin of Ti–Nb–Ta–Zr bearing minerals in the Abu Diab highly evolved granite from the Central Eastern Desert of Egypt

Petrogenesis of U- and Mo-bearing A2-type granite of the Gattar batholith in the Arabian Nubian Shield, Northeastern Desert, Egypt: Evidence for the favorability of host rocks for the origin of associated ore deposits

Subsequent Separation of Niobium (Nb), Thorium (Th), Rare Earth Elements (REEs), Zirconium (Zr), and Uranium (U) from Abu Rusheid Cataclastic Concentrate, South Eastern Desert, Egypt

Adel H. El-Afandy

Papers

Petrogenesis of U- and Mo-bearing A2-type granite of the Gattar batholith in the Arabian Nubian Shield, Northeastern Desert, Egypt: Evidence for the favorability of host rocks for the origin of associated ore deposits

Subsequent Separation of Niobium (Nb), Thorium (Th), Rare Earth Elements (REEs), Zirconium (Zr), and Uranium (U) from Abu Rusheid Cataclastic Concentrate, South Eastern Desert, Egypt