Burial and contact metamorphism in the Late Permian Broughton formation, Sydney basin, NSW, Australia
Two Late Permian shallow marine sandstones in the Sydney Basin were analyzed to determine the effects of burial and contact metamorphism on mineral assemblages. The sandstone units are overlain by basalt flows tens of meters thick and are intruded by basaltic dikes. The bulk mineralogy of the sandstones includes abundant quartz, plagioclase feldspar, calcite, laumontite and chlorite, with smaller amounts of microcline and hematite. The clay mineralogy is dominated by an interstratified chlorite-smectite, sometimes regularly ordered (R1) as corrensite. The chlorite-smectite is interpreted as an alteration product of volcaniclastic debris (glass shards or lithic fragments?) incorporated into the sediments during deposition. Upon burial and the generation of hydrothermal fluids in the sediment pile, laumontite formed from the alteration of plagioclase. Cart et al.(1999) have given evidence for several episodes of fluid circulation in the southern Sydney Basin and have suggested burial metamorphic temperatures in the range of～200 to 230 ℃. Near heat sources, such as in the contact zone between the overlying basalt flows and the sediments, and in the contact aureoles surrounding dikes,ehlorite-smectite is regularly ordered (R1) and is present as corrensite.
R.H.April E.Rampe J.Kaplan P.F.Carr
Department of Geology, Colgate University, Hamilton, NY, USA School of Earth and Environmental Sciences, University ofWollongong, NSW, Australia
国际会议
第十二届水-岩相互作用国际研讨会(P0roceedings of the 12th International Symposium on Water-Rock Interaction)
昆明
英文
53-56
2007-07-31（万方平台首次上网日期，不代表论文的发表时间）