Download to read offline
Laum Presen Segsa
- 1. F or mationAn d O c c ur r enc es Of Laumont it e And R el at ed Miner al s In Th e C ar o l in as And Vir gin ia , Mid dl e Mes o zoic Zeo l ite F ac ie s M etamor phis m, S o ut her n Appal ac hia n Pie d mont D onal d R . Pr iv et t, P.G . S .T .A . R. E nvir o nment al 1C ir c l e S t r eet G r eat F al l s , S C 29055
- 2. Presentation Time: AM11:40 AM-12:00 PM [email protected] Southeastern Section 60th Annual Meeting (23-25 March 2011) Session No. 4 Piedmont Geology: New Mapping and New Perspectives Wilmington Convention Center: Room 106
- 3. A 175 -195Ma hydrothermal zeolite grade metamorphic event altered most pre-Jurassic rocks Southern Appalachian Piedmont Central Georgia, South and North Carolina to Virginia
- 5. file:///Users/donprivett/Desktop/laumontite/PRVTT Fig1 PreviousLaumontite 1.jpg a
- 7. Zeolite grade thermalmetamorphism Zeolite facies represents All mineral, textural and chemical changes resulting from hot waters, steam or/and gas crystallization of fracture – filling and replacement zeolites and prehnite in host rocks
- 8. GENERAL GEOLOGY Area Neoproterozoic and Paleozoic igneous, metamorphic, and Triassic igneous and sedimentary rocks altered by period of zeolite grade regional thermal metamorphism Event evidenced by the laumontite filling fractures and replacing feldspars in intrusive and in older metamorphosed diorites and granites.
- 9. LAUMONTITE DISTRIBUTION Laumontite identifiedfrom over 100 separate locations in relatively unweathered outcrops rock exposed in foundations, trenches, quarries, mined caverns and in cores from borings for power plants and cuttings from water wells and exploratory test wells.
- 10. OCCURRENCE Laumontite occurs as:
- 11. (1)single pink and white euhedral crystals in druses and incompletely filled veins
- 12. (2)veinlets of matted interpenetrating crystal aggregates filling single and multiple narrow fractures and joints file:///Users/donprivett/Desktop/laumontite/scan0069.jpg
- 14. Biotite - microlinegranite porphyry cut by numerous pink asicular laumontite veinlets. file:///Users/donprivett/Desktop/laumontite/Untitled_003.jpg
- 15. Laumontite-calcite veinlet cuttingaltered diorite.
- 16. Interpenatrating asciular laumontitecrystals on fracture in diorite
- 17. (3) replacementof plagioclase forming partial to complete "mosaic pseudomorphs" composed of minute laumontite crystals and albite. file:///Users/donprivett/Desktop/laumontite/lau21.tif
- 18. Laumontite is best identified by microscopic study.
- 19. A. indiffuse plane light laumontized plagioclase displays a mottled texture file:///Users/donprivett/Desktop/laumontite/microlaumrpplag.jpg
- 21. B. polysynthetictwinning of plagioclase is destroyed, partly replaced plagioclase retains its twinning; however, it is mottled top plane light, same cross polars file:///Users/donprivett/Desktop/laumontite/lau21.tif
- 22. Calcite and radiatinglaumontite file:///Users/donprivett/Desktop/laumontite/tscalc copy.tif
- 23. Calcite and radiating laumontite
- 24.
- 25. Larger laumontite crystals, crossed polars.
- 26. Mixed calcitelaumontite crossed polars
- 27. Field exposure in saprolite/partialy weathered quartz monzonite - extensive laumontite replacement and veins white laumontite leonardite- Compass for scale 2
- 28. ZEOLITE PARAGENESIS Laumontite and other zeolites theoretical and experimental limit determinations and detailed paragenesis studies yield considerable disparity between theoretical and experimental temperature and pressure limits and substantially lower temperatures of natural formation . (Coombs,1952, Thompson, 1971, Frost, 1980 and Loui, 1971) (Boles and Coombs, 1977 and Suranam, 1973).
- 29. PARAMETERSTHOUGHT TO CONTROL TEMPERATURE AND PRESSURES OF NATURAL ZEOLITES IN ROCKS Experimentally determined temperatures are both higher and lower than values obtained under natural conditions Fluid pressure gradients activities of CO2, pH2O ratio of water and CO2 the permeability nucleation and reaction kinetics oxygen fugacity presence of additional ions all can alter the temperatures of formation Boles and Coombs (1977)
- 30. Laumontite Stability LimitsVary Widely upper limits of 230º – 325º at 0.5 kb, 250º at 2.75 kb. Thompson (1971) Loui (1971) lower limit even greater conflict compared 150º - 200º C at 1 kb where p = p (Loui, 1971) lowest recorded temperature of formation 43º C crystallized at Suspe Hot Springs, California. In buried sedimentary rocks estimates of 50º C laumontite - 90º C for prehnite (Boles and Coombs, 1977) 75º + 5° C for laumontite in hot springs (Castino and Sparks, 1974, Siki, 1969 ) calcite fluid inclusions in laumontite filled amygdules of lava flows, Iceland 140º - 200º C. Meghan, Robinson and Delaney (1982)
- 31. Zeolites occur in geothermal areas of Iceland a. in California metamorphic rocks b. New Zealand thermal areas c. Southeastern Piedmont U.S.A. a. (Kristmannedottir and Tomanson,1978), (Mehegan, Robinson and Delaney, 1982) b. (Madsen and Murata, 1970) c. (Barnes, 1977)
- 32. Laumontite present inthe majority of rock exposed in the Piedmont gneiss of the Inner Piedmont metamorphosed and unmetamorphosed igneous rock metasedimentary rocks of the Charlotte Belt and the Kings Mountain Belt metavolcanic and metasedimentary rock Carolina Slate Belt and in Buried Triassic - Jurassic sedimentary and igneous rocks
- 33. discovery of laumontitein buried Triassic rocks - cored basement below the Triassic of South Carolina and south central Georgia suggest that laumonatization is even more extensive laumontite fills amygdules and replaces plagioclase in a 184 +/- 3 my basalt from Dorchester county, S.C. (Gottfried et.al.,1983) present in Triassic sedimentary and older igneous rocks from South Central Georgia (Chowns and Williams,1983)
- 34. Laumontite imparts apinkish color to the altered and replaced plagioclase. appears to be directly proportional to the intensity of laumonatization laumontite and calcite fill vein interiors
- 35. x-ray reflections varywith the relative humidity material is best described as laumontite-leonhardite. Laumontite readily dehydrates to leonhardite unless the sample is kept under conditions of 100% relative humidity
- 36. ORIGIN Pangea breakup Tectonic activity about 170 -150 mya - Triassic and Jurassic separation of North America and Africa fractured old weaker shears, formed new joints and faults.
- 37. SUMMARY Heatedcirculating groundwaters mixed with hydrothermal solutions fluids reacted with plagioclase prehnite and laumontite. Excessive calcium reacted with silica to produce the fracture filling laumontite, calcite other lower temperature zeolites. Two generations of diabase dikes are evident; suggesting that igneous activity persisted as the stress changed. zeolite grade thermal alteration metamorphism is widespread in rocks of the southern Appalachian rocks.
- 38. Immature clastics depositedin subsiding half grabens generation of basaltic magmas basalt flows in Triassic sedimentary rock intrusion of diabase dikes and basaltic to diabase sills. .
- 39. Thank You –Have a great day