The integrated CL method and the Paparoa Trough: a new approach to provenance analysis

• Main Author: Ettmuller, Franz
• Format: Other/Unknown Material
• Language: English
• Published: 2003
• Subjects: Greenland; New Zealand
• Online Access: https://hdl.handle.net/10092/105195; https://doi.org/10.26021/14290

The Integrated CL method is a new approach usmg grain-by-grain comparison to integrate scanning electronmicroscope cathodoluminescence (SEM-CL) imaging of quartz into standard provenance analysis by optical microscopy of quartzose sediments. SEM-CL shows CL characteristics and features such as homogeneous, patchy, mottled, zoned, dark or light luminescence, microcracks, light or dark linear features and intragrain boundaries. Petrography shows extinction behaviour, polycrystallinity, grain roundness, shape and size. Graphic illustration of grain properties and their combinations helped to discover significant trends. Grains with straight extinction followed the same trend as grains with dark CL appearance indicating that, in this case, straight extinction behaviour is from disaggregation of polycrystalline quartz. Light linear features, interpreted as unhealed alterations, show the same trend as dark CL and strong undulosity characteristic of metamorphic quartz indicating they were more vulnerable to surface damage. Dark linear features document fracturing and healing during a previous sedimentary cycle, thus identify recycled grains. A common trend, of decrease in frequency up section, of quartz grains showing dark linear features with different extinction behaviour suggested the presence of a higher-grade metamorphic source. This Integrated CL method was used to investigate the provenance of fluvial/lacustrine quartz-rich lithic arenites deposited in the Late Cretaceous extensional Paparoa Trough, New Zealand. Results showed that in the west of the basin the quartz grains were chiefly of metamorphic origin supplied from the metasediments of the Greenland Group and only about 15% of the grains were identified as plutonic derived probably from local plutons such as the Barrytown Granite. In the east the two stratigraphically lower units, the Jay and the Ford Members, were supplied with sediments from the west and resemble that composition. The overlying units received their sediments from the NE dominantly from ...