(1) Field observation and age frequcnee spectra indicate that Mesozoic granitesin the Nanling region arc of non-orogenic origin and must be divided in aecordance with stratigraphic timescale rather than with geotectonic cycles. (2) Isotopic ages indicate that some batholiths in the axial part of Caledoniar belts belong to Mesozoic granites. However, field observation and laboratory studies show that they were primarily formed during the early Paleozoic era and have been subjected to alteration of various degrees. (3) With regard to intrusions which isotopic ages are older than that defined by stratigraphic evidences, isotopic measurements will provide the true age of formation of the massivea while stratigraphic evidence should be taken as reflection of local regeneration.
展开▼
