Abstract
Regional variations in initial 87Sr/86Sr ratios (r i) of Mesozoic plutons in central Idaho locate the edge of Precambrian continental crust at the boundary between the late Paleozoic-Mesozoic accreted terranes and Precambrian sialic crust in western Idaho. The r i values increase abruptly but continuously from less than 0.704 in the accreted terranes to greater than 0.708 across a narrow, 5 to 15 km zone, characterized by elongate, lens-shaped, highly deformed plutons and schistose metasedimentary and metavolcanic units. The chemical and petrologic character of the plutons changes concomitantly from ocean-arc-type, diorite-tonalite-trondhjemite units to a weakly peraluminous, calcic to calcalkalic tonalite-granodiorite-granite suite (the Idaho batholith). Plutons in both suites yield Late Cretaceous ages, but Permian through Early Cretaceous bodies are confined to the accreted terranes and early Tertiary intrusions are restricted to areas underlain by Precambrian crust. The two major terranes were juxtaposed between 75 and 130 m.y. ago, probably between 80 and 95 m.y.
Oxygen and strontium isotopic ratios and Rb and Sr concentrations of the plutonic rocks document a significant upper-crustal contribution to the magmas that intrude Precambrian crust. Magmas intruding the arc terranes were derived from the upper mantle/subducted oceanic lithosphere and may have been modified by anatexis of earlier island-arc volcanic and sedimentary units.
Plutons near the edge of Precambrian sialic crust represent simple mixtures of the Precambrian wall-rocks with melts derived from the upper mantle or subducted oceanic lithosphere with r i of 0.7035. Rb/Sr varies linearly with r i, producing “pseudoisochrons” with apparent “ages” close to the age of the wall rocks. Measured δ 18O values of the wall rocks are less than those required for the assimilated end-member by Sr-O covariation in the plutons, however, indicating that wall-rock δ 18O was reduced significantly by exchange with circulating fluids. Metasedimentary rocks of the Belt Supergroup are similarly affected near the batholith, documenting a systematic depletion in 18O as much as 50 km from the margin of the batholith.
Plutons of the Bitterroot lobe of the Idaho batholith are remote from the accreted terranes and represent mixtures of Precambrian wall-rocks with melts dominated by continental lower crust (r i>0.708) rather than mantle. “Pseudoisochrons” resulting from these data are actually mixing lines that yield apparent “ages” less than the true age of the wall rocks and meaningless “ri”. Assimilation/ fractional-crystallization models permit only insignificant amounts of crystal fractionation during anatexis and mixing for the majority of plutons of the region.
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References
Allegre CJ, Ben Othman D (1980) Nd-Sr isotopic relationship in granitoid rocks and continental crust developement. A chemical approach to orogensis. Nature 286:335–342
Armstrong RL (1974) Geochronometry of the Eocene volcanic-plutonic episode in Idaho. Northwest Geology 3:1–15
Armstrong RL (1975) The geochronometry of Idaho. Isochron/West, 14:1–50
Armstrong RL (1976) The geochronometry of Idaho. Isochron/West 15:1–33
Armstrong RL, Taubeneck WH, Hales PO (1977) Rb-Sr and K-Ar geochronometry of Mesozoic granitic rocks and their Sr isotopic composition, Oregon, Washington, and Idaho. Geol Soc Am Bull 88:397–411
Ave' Lallemant HG, Phelps DW, Sutter JF (1980) 40Ar-39Ar ages of some pre-Tertiary plutonic and metamorphic rocks of eastern Oregon and their geologic relationships. Geology 8:371–374
Bateman PC (1979) Cross section of the Sierra Nevada from Madera to the White Mountains, central California. Geological Society of America Map, MC-28E, sheet 1
Bickford ME, Chase RB, Nelson BK, Shuster RD, Arruda EC (1981) U-Pb studies of zircon cores and overgrowths, and monazite: implications for age and petrogenesis of the northern Idaho batholith. J Geol 89:433–457
Bond JG (1978) Geologic map of Idaho. Idaho Bureau of Mines and Geology
Borthwick J, Harmon RS (1982) A note regarding ClF3 as an alternative to BrF5 for oxygen isotope analyses. Geochim Cosmochim Acta 46:1665–1668
Briqueu L, Lancelot JR (1979) Rb-Sr systematics and crustal contamination models for calcalkaline series. Earth Planet Sci Lett 43:385–396
Brooks HC, Vallier TL (1978) Mesozoic rocks and tectonic evolution of eastern Oregon and western Idaho. In: Howell DG, McDougall KA (eds) Mesozoic paleogeography of the western United States: Soc. Econ. Paleon. Mineral., Pacific Section, Pacific Coast. Paleogeography Symposium 2:133–145
Brown GM, Holland JG, Sigurdsson HG, Tomblin JF, Arculus RJ (1977) Geochemistry of the Lesser Antilles volcanic arc. Geochim Cosmochim Acta 41:785–801
Chase RB, Bickford ME, Tripp SE (1978) Rb-Sr and U-Pb isotopic studies of the northeastern Idaho batholith and border zone. Geol Soc Am Bull 89:1325–1334
Chase RB, Bickford ME, Arruda EC (1983) Tectonic implications of Tertiary intrusion and shearing within the Bitterroot dome, northeastern Idaho batholith. J Geol 91:462–470
Church SE, Tilton GR (1973) Lead and strontium isotopic studies on the Cascade Mountains: Bearing on andesite genesis. Geol Soc Am Bull 84:431–454
Clayton RN, Mayeda TK (1963) The use of bromine penta-fluoride in the extraction of oxygen from oxide and silicates for isotopic analysis. Geochim Cosmochim Acta 27:43–52
Craig H (1961) Standard for reporting concentrations of deuterium and oxygen-18 in natural waters. Science 133:1833–1834
Criss RE, Fleck RJ (1984) An 18O/16O, D/H, 87Sr/86Sr, and K-Ar study of the northern Idaho batholith. U.S. Geol Survey Prof Pap (in press)
Criss RE, Lanphere MA, Taylor HP Jr (1982) Effects of regional uplift, deformation, and meteoric-hydrothermal metamorphism on K-Ar ages of biotites in the southern half of the Idaho batholith. Geophy Res 87:7029–7046
Criss RE, Taylor HP Jr (1983) An 18O/16O and D/H study of Tertiary hydrothermal systems in the southern half of the Idaho batholith: Geol Soc Am Bull 94:640–663
Dalrymple GB, Lanphere MA (1969) Potasium-argon dating: Principles, techniques, and application to geochronology. San Francisco, Calif Freeman p 258
DePaolo DJ (1981) Trace element and isotopic effects of combined wallrock assimilation and fractional crystallization. Earth Planet Sci Lett 53:189–202
DePaolo DJ, Wasserburg GJ (1977) The sources of island arcs as indicated by Nd and Sr isotopic studies. Geophys Res Lett 4:465
DePaolo DJ, Wasserburg GJ (1979) Petrogenetic mixing models and Nd-Sr isotopic patterns. Geochim Cosmochim Acta 43:615–627
Doe BR, Leeman WP, Christiansen RL, Hedge CE (1982) Lead and strontium isotopes and related trace elements as genetic tracers in the upper Cenozoic rhyolite-basalt association of the Yellowstone Plateau volcanic field. J Geophys Res 87:4785–4806
Domenick MA, Kistler RW, Dodge FCW, Tatsumoto M (1983) Nd and Sr isotopic study of crustal and mantle inclusions from the Sierra Nevada and implications for batholith petrogenesis: Geol Soc Am Bull 94:713–719
Eslinger EV, Savin SM (1973) Oxygen isotope geothermal of the burial metamorphic rocks of the Precambrian Belt Supergroup, Glacier National Park, Montana. Geol Soc Am Bull 84:2549–2560
Faure G, Bowman JR, Elliot DH, Jones LM (1974) Strontium isotopic composition and petrogenesis of the Kirkpatrick basalt, Queen Alexandra Range, Antarctica. Contrib Mineral Petrol 48:153–169
Faure G, Powell JL (1972) Strontium Isotope Geology, Springer, Berlin Heidelberg New York, p 188
Field CW, Jones MB, Bruce WR (1973) Porphyry copper-molybdenum deposits of the Pacific Northwest. AIME
Fleck RJ, Greenwood WR, Hadley DG, Anderson RE, Schmidt DL (1980) Rubidium-strontium geochronology and plate-tectonic evolution of the southern part of the Arabian Shield. US Geol Surv Prof Pap 1131:33
Friedman I (1953) Deuterium content of natural waters and other substances. Geochim Cosmochim Acta 4:89–103
Garlick GD, Epstein S (1967) Oxygen isotope ratios in coexisting minerals of regionally metamorphosed rocks. Geochim Cosmochim Acta 31:181–214
Garmezy L, Sutter JF (1983) Mylonitization coincident with uplift in an extensional setting, Bitterroot Range, Montana-Idaho: Geol Soc Am Abst with Prog 15:578
Gregory RT, Taylor HP Jr (1981) An oxygen isotope profile in a section of Cretaceous oceanic crust, Samail ophiolite, Oman: Evidence for (δ18O-buffering of the oceans by deep (>5km) seawater-hydrothermal circulation at mid-ocean ridges. J Geophys Res 86:2737–2755
Hamilton Warren (1963) Metamorphism in the Riggins region, western Idaho. US Geol Surv Prof Pap 436:95
Hawkesworth CJ, O'Nions RK, Arculus RJ (1979) Nd and Sr isotope geochemistry of island arc volcanics, Grenada, Lesser Antilles. Earth Planet Sci Lett 45:237–248
Hietanen A (1962) Metasomatic metamorphism in western Clearwater County, Idaho, US Geol Surv Prof Pap 344A:116
Hietanen A (1963a) Metamorphisim of the Belt Series in the Elk River-Clarkia area, Idaho. US Geol Surv Prof Pap 344-C:49
Hietanen A (1963b) Idaho batholith near Pierce and Bungalow, Clearwater County, Idaho. US Geol Surv Prof Pap 344-D: 42
Hietanen A (1967) Scapolite in the Belt Series in the St. Joe-Clearwater Region, Idaho. Geol Soc Am Spec Pap 86:56
Holloway CD (1980) Possible Eocene (?) caldera-margin volcanic sequence, southern Bitterroot Mountains, Montana: Geol Soc Am Abstr with Prog 12:275
Hyndman DW (1981) Controls on source and depth of emplacement of granitic magma Geology 9:244–249
Kay RW, Sun S-S, Lee-Hu C-N (1978) Pb and Sr isotopes in volcanic rocks from the Aleutian Islands and Pribilof Islands, Alaska. Geochim Cosmochim Acta 42:263–273
Kistler RW (1974) Phanerozoic batholiths in western North America: A summary of some recent work on variations in time, space, chemistry and isotopic compositions: Earth Planet Sci Lett Ann Rev 2:403–418
Kistler RW, Ghent ED, O'Neil JR (1981) Petrogenesis of garnet two-mica granites in the Ruby Mountains, Nevada. J Geophys Res 86:10591–10606
Kistler RW, Peterman ZE (1973) Variations in Sr, Rb, K, Na, and initial 87Sr/86Sr in Mesozoic granitic rocks and intruded wall rocks in central California: Geol Soc Am Bull 84:3489–3512
Kistler RW, Peterman ZE (1978) Reconstruction of crustal blocks of California on the basis of initial strontium isotopic composition of Mesozoic granitic rocks: US Geol Surv Prof Paper 1071:17
Langmuir CH, Vocke RD, Hanson GN, Hart SR (1978) A general mixing equation: applied to the petrogenesis of basalts from Iceland and Rekjanes Ridge: Earth Planet Sci Lett 37:380–392
Larsen ES Jr, Schmidt RG (1958) A reconnaissance of the Idaho batholith and comparison with the southern California batholith: US Geol Surv Bull 1070-A:1–33
Magaritz M, Whitford DJ, James DE (1978) Oxygen isotopes and the origin of high 87Sr/86Sr andesites. Earth Planet Sci Lett 40:220–230
Masi U, O'Neil JR, Kistler RW (1981) Stable isotope systematics in Mesozoic granites of central and northern California and southwestern Oregon. Contrib Mineral Petrol 67:116–126
McCulloch MT, Perfit MR (1981) 143Nd/144Nd, 87Sr/86Sr and trace element constraints on the petrogenesis of Aleutian islands are magmas. Earth Planet Sci Lett 56:167–179
Meyers PE (1982) Geology of the Harpster area, Idaho County, Idaho. Idaho Bur Mines Geol, Bull 25:46
Moore JG (1959) The quartz diorite boundary line in the western United States. J Geol 67:198–210
Norrish K, Chappell BW (1967) X-ray flourescence spectrography. In: Zussman J (ed) Physical methods in determinative mineralogy. Academic Press, London, p 161–214
O'Neil JR, Chappell BW (1977) Oxygen and hydrogen isotope relations in the Berridale batholith. J Geol Soc London 133:559–571
Pankhurst RJ, Pidgeon RT (1976) Inherited isotope systems and the source region pre-history of early Caledonian granites in the Dalradian series of Scotland. Earth Planet Sci Lett 31:55–68
Peterman ZE (1979) Strontium isotope geochemistry of late Archean to Late Cretaceous tonalites and trondhjemites, chapter 4. In: Barker F (ed) Dacites, trendhjemites, and related rocks: Elsevier Amsterdam, pp 133–147
Schmidt DL (1964) Reconnaissance petrographic cross section of the Idaho batholith in Adams and Valley Counties, Idaho. US Geol Surv Bull 1181-G:50
Shieh YN, Taylor HP Jr (1969) Oxygen and hydrogen isotope studies of contact metamorphism in the Santa Rosa Range, Nevada, and other areas. Contrib Mineral Petrol 20:306–356
Sheppard SMF, Epstein S (1970) D/H and 18O/16O ratios of minerals of possible mantle or lower crustal origin. Earth and Planet Sci Lett 9:232–239
Snee LW, Sutter JF, Zen E-an (1983) Ages of emplacement and cooling history of the Pioneer batholith, southwestern Montana: Geol Soc Am Abstr with Prog 15:412
Stern RJ (1982) Strontium isotopes from circum-Pacific intraoceanic islands arcs and marginal basins: regional variations and implication for magmagnesis: Geol Soc Am Bull 93:477–486
Steiger RH, Jager E (1977) Subcommission on geochronology: Convention on the use of decay constants in geo-and cosmochronology: Earth Planet Sci Lett 36:359–362
Suhr NH, Ingamells CO (1966) Solution technique for analysis of silicates. Anal Chem 38:730–734
Swanberg CA, Blackwell DD (1973) Areal distribution and geophysical significance of heat generation in the Idaho batholith and adjacent intrusions in eastern Oregon and western Montana. Geol Soc Am Bull 84:1261–1282
Taubeneck WH (1959) Age of granitic plutons in eastern Oregon [abs]. Geol Soc Am Bull 70:1685
Taubeneck WH (1971) Idaho batholith and its southern extension. Geol Soc Am Bull 82:1899–1928
Taylor HP Jr (1974) Oxygen and hydrogen isotopic evidence for large-scale circulation and interactions between ground waters and igneous intrusions, with particular reference to the San Juan volcanic field, Colorado. In: Hofmann AW, Giletti BJ, Yoder HS Jr, Yund RA (eds) Geochemical transport and kinetics. Carnegie Inst Wash Publ 634:299–324
Taylor HP Jr (1977) Water/rock interactions and the origin of granitic batholiths. J Geol Soc London 133:509–558
Taylor HP Jr (1980) The effects of assimilation of country rocks by magmas on 18O/16O and 87Sr/86Sr systematics in igneous rocks. Earth Planet Lett 47:243–254
Taylor HP Jr, Magaritz M (1978) Oxygen and hydrogen isotope studies of the Cordilleran batholiths of western North America. In: Robinson BW (ed) Stable isotopes in the earth sciences. New Zealand Dep Sci Indust Res Bull 220:151–173
Taylor HP, Silver LT (1978) Oxygen isotope relationships in plutonic igneous rocks of the Peninsular Ranges batholith, southern and Baja California: Short Papers of the Fourth International Conference on Geochronology, Cosmochronology, and Isotope Geology. US Geol Surv Open-File Report 78-701, p 423–426
Thayer TP, Brown CE (1964) Pre-Tertiary orogenic and plutonic intrusive activity in central and northeastern Oregon. Geol Soc Am Bull 75:1255–1262
Toth MI (1983) Reconnaissance geologic map of the Selway-Bitterroot wilderness, Idaho County, Idaho, and Missoula and Ravalli Counties, Montana. US Geol Surv Map, MF-1495-B, 1∶125,000 scale, with text
Turi B, Taylor HP Jr (1971) An oxygen and hydrogen isotope study of a granodiorite pluton from the southern California batholith. Geochim Cosmochim Acta 35:383–406
Vallier TL, Brooks HC, Thayer TP (1977) Paleozoic rocks of eastern Oregon and western Idaho. In: Stewart JH, and others (eds) Paleozoic paleogeography of the western United States: Society of Economic Palentologists and Mineralogists, Pacific Section, Pacific Coast Paleogeography Symposium 1:455–466
Vollmer R (1976) Rb-Sr and U-Th-Pb dystematics of alkaline rocks: the alkaline rocks from Italy. Geochim Cosmochim Acta 40:283–295
Vollmer R, Norry MJ (1983) Possible origin of K-rich volcanic rocks from Virunga, East Africa, by metasomatism of continental crustal material: Pb, Nd, and Sr isotopic evidence: Earth Planet Sci Lett 64:374–386
Walker NW (1983) Pre-Tertiary tectonic evolution of northeastern Oregon and west-central Idaho: Constraints based on U/Pb ages of zircons: Geol Soc Am Abstr with Prog 15:371
Whitford DJ (1975) Strontium isotopic studies of the volcanic rocks of the Sunda arc, Indonesia, and their petrogenetic implications: Geochim Cosmochim Acta 39:1287–1302
Withford DJ, Jezek PA (1982) Isotopic constraints on the role of subducted sialic material in Indonesian island-arc magmatism. Geol Soc Am Bull 93:504–513
York D (1969) Least-squares fitting of a straight line with correlated errors. Earth Planet Sci Lett 5:320–324
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Fleck, R.J., Criss, R.E. Strontium and oxygen isotopic variations in Mesozoic and Tertiary plutons of central Idaho. Contr. Mineral. and Petrol. 90, 291–308 (1985). https://doi.org/10.1007/BF00378269
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DOI: https://doi.org/10.1007/BF00378269