Single-grain detrital muscovite Rb-Sr isotopic composition as an indicator of provenance for the Carboniferous sedimentary rocks in northern Dabie, China

Abstract

Low-grade metamorphic Paleozoic sedimentary rocks are exposed along the northern margin of the Qinling-Dabie orogenic belt that formed by the collision of the North and South China blocks during the Early Mesozoic. Geological provenance and tectonic setting of these low-grade sedimentary rocks are strongly debated. Recent studies have shown that they contain Paleozoic, Late Proterozoic and Late Archean detrital zircons, which points to an origin from different sources including rocks from the South and North China blocks. This study presents single-grain mineral Rb-Sr results for detrital muscovites and biotites from Carboniferous sedimentary sequences of the Beihuaiyang low-grade metamorphic zone exposed along the northern margin of the Dabie Mountains. About 15% of detrital muscovite grains are phengitic in composition with high Si/Al ratios of >3.3. Single grain Rb-Sr isotopic analyses show that both muscovites and phengites give a pooled age of about 420 Ma, implying Middle Paleozoic thermal and high-pressure metamorphic events in the source area(s). Rb-Sr isotopic evidence from detrital biotites suggests at least two different sedimentary sources of old crustal rocks and juvenile material. The latter probably comprised magmatic rocks related to the Paleozoic convergence along the southern margin of the North China block. Whole-rock Sm-Nd isotopic composition of the sedimentary rocks also demonstrates a mixture of sedimentary sources of different ages that confirm conclusions proposed previously from evidence of detrital zircon ages. We conclude that the Paleozoic detrital phengites originate from Paleozoic subduction and subsequent collision proposed for the North Qinling terrane. Our study shows that, single-grain detrital mica Rb-Sr isotopic characteristics can be a potential indicator for the provenance of geological complex terranes.

On depositional processes governing along‐strike facies variations of fine‐grained deposits: Unlocking the Little Ice Age subaqueous clinothems on the Adriatic shelf

“…Mulder et al ., 2003; Mutti et al ., 2003; Zavala et al ., 2011; Li et al ., 2015) and thought to reflect the record of river flood pulses in the prodelta slope (Pellegrini et al ., 2021). Peaks in the Zr/Rb ratio denote a markedly coarser grain size of these layers (Dypvik & Harris, 2001; Chen et al ., 2009). A river‐dominated depositional system, supplied exclusively by Apennine rivers without influence from the Po, is suggested by comparatively low Ni counts and by an abundance of carbonate rock fragments (Amorosi et al ., 2022).…”

Rb–Sr Dating of Gold‐Bearing Pyrite in the Jinchang Porphyry Cu–Au Deposit, Heilongjiang Province, NE China

“…Single‐grain dating of microsamples of minerals associated with gold formation, under low blank levels and with precise mass spectrometric techniques, has been successfully applied to quartz, pyrite, and sericite in determining the timing of mineralization (Li et al, ; Chen et al, ). Rb–Sr dating of sulfide minerals, particularly sphalerite and pyrite, is often used to date the formation of hydrothermal deposits (Brannon et al, ; Christensen et al, ; Yang & Zhou, ; Hou et al, ), although it has not always been successful.…”

Strontium, Hydrogen and Oxygen Behavior in Vent Fluids and Plumes from the Kueishantao Hydrothermal Field Offshore Northeast Taiwan: Constrained by Fluid Processes

“…The 87 Sr/ 86 Sr was measured using thermal ionization mass spectrometry (TIMS; Triton) at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences. The procedures of chemical separation and determination were described in detail in previous studies [48,49]. For Sr, the procedural blanks were less than 50 pg.…”