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Home My WebLink AboutGMC Data Report No. 219 Apatite fission track data from the Paul G. Benedum Nulato Unit No.1 well. r:~ GE~O'¿Q ('-.1: S. ~( _ <Ã> () Received 8 September 1993 Total of 10 pages in report Alaska Geologic Materials Center Data Report No. 219 Apatite fission track data from Nulato Unit #1 well, western Alaska John M. Murphy August 1993 The following fission track data sheets summarize apatite fission track age and track length data from the Nulato Unit #1 well in tabular fonnat. The study was part of a Ph.D. Dissertation on the thennal history of the Yukon-Koyukuk Basin and Borderlands. Samples were composited over -500' intervals from washed ditch cuttings and con sited of up to 20 teaspoons, one each 30 feet, until sufficient material was obtained (generally 0.5-1.0 kg). Apatite grains were separated using conventional grinding and mineral extraction techniques. Yields were poor to very poor and the data by itself is of marginal quality. Finished slides, residual materials and unprocessed samples (odd numbers) are stored at the Geologic Materials Center- Eagle River, Alaska. To reveal spontaneous fission tracks apatite grains were mounted in epoxy resin on glass slides, '. ground and polished to expose internal surfaces, then etched in 5N Nitric acid for 18-20 seconds. To detect induced fission fragments escaping apatite grains during irradiation Uranium-free muscovite external detectors were attatched to each grain-mount. After irradiation the mica detectors were etched for 18-25 minutes in concentrated hydrofluoric acid to reveal induced fission tracks. Neutron irradiations, perfonned at the Australian Atomic Energy Commissions HIFAR reactor, were subsidized by a grant to the La Trobe University Fission Track Research Group. U sing facilities of the Fission Track Research Group, La Trobe University, Australia fission tracks were counted and measured at 1250x in transmitted light using a dry 80x objective. Ages were determined using the zeta-calibrated external detector method and appropriately modified fission track age equation (e.g. Hurford and Green, 1982, 1983). Errors, reported as I-sigma, were calculated using the techniques of Green (1981). Fully- etched and horizontal confined fission tracks were measured using a projection tube and calibrated digitizing pad. Track length data is given in Table 1 (errors are 2-sigma). GMC Data Report No. 219 1/10 The program 'Mactrack', developed by the Melbourne fission track community, was used for age calculations and fonnatting of the data sheets below. The following page explains categories given on individual age data sheets. Number NUl NU2 NU3 NU4 NU5 NU6 NU7 NU8 NU9 NU10 NUll NU12 Depth (m) 76 381 686 991 1295 1600 1905 2210 2515 2819 3124 3429 Sample Status Status Unprocessed Apatite fission track age and length data Unprocessed Apatite fission track age data only Unprocessed No apatite in sample, thus no age or length data Unprocessed Apatite fission track age and length data Unprocessed Apatite fission track age data only Unprocessed Apatite fission track age and length data Selected References Green, P.F., 1981, A new look at statistics in fission track dating. Nuclear Tracks, v. 5, p. 77- 86. Hurford, A.J. and Green, P.F., 1982, A users' guide to fission track dating: Earth and Planetary Sci. Letters, v. 59, p. 343-354. Hurford, AJ. and Green, P.F., 1983, The zeta age calibration of fission-track dating: Chemical Geology (Isotope Geoscience Section), v. 1, p. 285-317. GMC Data Report No. 219 2/10 Sample Number MINERAL DATED ELEVATION (depth ft./m)- AREA La Trobe University J.D. NUMBER; All samples analyzed by John M. Murphy (JM) No. Ns Ni No. Ns Ni Na RATIO U(ppm) RHOs RHOi F. T.AGE (Ma) 519 1627 Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) - Apatite grain number for this sample ~ Number of spontaneous tracks counted on mineral surface - Nwnber of spontaneous tracks counted on mica detector surface - Number of counting areas, whose area is given below; used to determine U(ppm) ~ Ratio of Ns/Ni ~ Uranium concentration in the mineral grain; ppm- parts per million - Spontaneous track density - Induced track density (ends of tracks escaping apatite surface counted on mica) - Single grain age with a I-sigma error 37.7 1.102E+06 3.453E+06 Area of basic unit = counting area of individual grid squares (squares/cm2); used in calculating (U)ppm, RHOs and RHOi and RHOD CHI SQUARED = statistical test to deterimine if single grain ages form a single population (Galbraith, 1981). >5% is a PASS, < 5% is a FAIL; PASS· means MEAN AGE is reported because there were less than 5 grains P(chi squared) = le~s than 5% means non-poissanian distribution so MEAN AGE is reported CORRELATION COEFFICIENT = 0.926 Linear regression of single grain ages V ARIANCE OF SQR(Ns) = 2.234059 CUlTently unused statistic V ARIANCE OF SQR(Ni) = 8.658181 CUlTently unused statistic Ns/Ni = 0.319 ± 0.016 Ratio used in calculating POOLED AGE. Mean of sum of Ns/Ni (i.e. 519/1627). For single population Ratio used in calculating MEAN AGE. Average Ns/Ni ratio of all single grains. For mixed populations MEAN RATIO = 0.356 ± 0.029 Calculated using total spontaneous (N s) and induced (Ni) track counts in the ratio NsjNi. Underlined if PASS Calulated using NsfNi ratios of individual grains (i.e. MEAN RATIO). Underlined if FAIL Ages calculated using a zeta of 350 ± 10 for SRM612 glass (see Appendix A) RHO D = (tracks/cm2); ND = number of tracks counted on mica detector adjacent to dosimetry glass NBS-SRM612; used in detennining RHO D. POOLED AGE = 66.6 ± 4.0 Ma MEAN AGE = 74.2 ± 6.4 Ma * Mean age reported due to low (U)ppm, <5; or low numbers of grains, <5. GMC Data Report No. 219 3/10 4/10 GMC Data Report No. 219 IRRADIATION LUl60-10; COUNTED BY: JM No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 9 46 10 0.196 25.6 9.990E+05 5.106E+06 88.7± 32.4 2 1 5 25 0.200 1.1 4.440E+04 2.220E+05 90.6± 99.3 3 0 1 6 0.000 0.9 O.oooE+oo 1.850E+05 O.o± 0.0 4 9 56 12 0.161 26.0 8.325E+05 5.180E+06 72.9± 26.3 5 1 12 4 0.083 16.7 2.775E+05 3.330E+06 37.9± 39.5 6 2 5 10 0.400 2.8 2.220E+05 5.550E+05 180.0±150.7 7 15 65 15 0.231 24.2 1.110E+06 4.810E+06 104.5± 30.1 8 0 3 9 0.000 1.9 O.oooE+oo 3.700E+05 O.o± 0.0 9 3 31 10 0.097 17.3 3.330E+05 3.441E+06 44.0± 26.6 10 2 17 14 0.118 6.8 1.586E+05 1.348E+06 53.5± 40.0 11 0 0 16 0.000 0.0 O.OOOE+OO O.OOOE+oo O.o± 0.0 12 40 259 16 0.154 90.3 2.775E+06 1.797E+07 70.1± 12.1 13 13 45 12 0.289 20.9 1.202E+06 4.162E+06 l30.5± 41.3 95 545 19.1 6.632E+05 3.805E+06 Area of basic unit = 9.009E"()7 cm-2 CHI SQUARED = 7.792746 WITH 12 DEGREES OF FREEDOM; PASS P(chi squared) = 80.1 % CORRELATION COEFFICIENT = 0.979 VARIANCE OF SQR(Ns) = 3.461296 V ARIANCE OF SQR(Ni) = 17.92451 Ns/Ni = 0.174 ± 0.019 MEAN RATIO = 0.148 ± 0.033 POOLED AGE = 79.1 ± 9.1 Ma MEAN AGE = 67.3 ± 15.1 Ma Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.608E+06cm-2; ND = 5868 NU2 APATITE -1,000' TO -1,500' (average -381m) NULATO WELL NU4 APATITE -3000' TO -3500' (average -991m) NULATO WELL IRRADIATION LUl60-11; COUNTED BY: JM No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 21 220 25 0.095 49.1 9.324E+05 9.768E+06 43.4± 10.0 2 4 39 16 0.103 13.6 2.775E+05 2.706E+06 46.6± 24.5 3 1 5 49 0.200 0.6 2.265E+04 1. 133E+05 90.6± 99.3 4 0 4 49 0.000 0.5 O.OOOE+OO 9.061E+04 O.o± 0.0 5 1 2 40 0.500 0.3 2.775E+04 5.550E+04 224.3±274.7 6 0 2 40 0.000 0.3 O.OOOE+OO 5.550E+04 O.o± 0.0 7 2 6 64 0.333 0.5 3.469E+04 1.041E+05 150.4±122.9 8 27 92 40 0.293 12.8 7.492E+05 2.553E+06 132.6± 29.3 56 370 6.4 1.924E+05 1.272E+06 Area of basic unit = 9.009E-07 cm-2 CHI SQUARED = 17.22372 WITH 7 DEGREES OF FREEDOM; FAIL P(chi squared) = 1.6 % CORRELATION COEFFICIENT = 0.815 VARIANCE OF SQR(Ns) = 3.878117 VARIANCE OF SQR(Ni) = 24.02362 Ns/Ni = 0.151 ± 0.022 MEAN RATIO = 0.191 ± 0.062 POOLED AGE = 68.7 ± 10.1 Ma MEAN AGE = 86.4 ± 28.3 Ma Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.608E+06cm-2; ND = 5868 GMC Data Report No. 219 5/10 NU8 APATITE -7000' TO -7500' (average -2210m) NULATO WELL IRRADIATIONLUl60-13; COUNTED BY: JM No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 1 7 5 0.143 7.8 2.220E+05 1.554E+06 64.9± 69.4 2 1 3 5 0.333 3.3 2. 220E+05 6.660E+05 150.4±173.7 3 22 33 16 0.667 11.5 1.526E+06 2.289E+06 297.3± 82.4* 4 0 1 4 0.000 1.4 O.OOOE+OO 2.775E+05 O.o± 0.0 5 0 5 16 0.000 1.7 O.OOOE+OO 3.469E+05 O.O± 0.0 6 1 9 40 0.111 1.3 2.775E+04 2.498E+05 50.5± 53.3 7 6 60 8 0.100 41.8 8.325E+05 8.325E+06 45.5± 19.5 8 0 0 32 0.000 0.0 O.OOOE+OO O.OOOE+OO O.o± 0.0 9 0 1 9 0.000 0.6 O.OOOE+OO 1.233E+05 O.o± 0.0 10 9 86 30 0.105 16.0 . 3.330E+05 3.182E+06 47.6± 16.7 11 6 11 9 0.545 6.8 7.400E+05 1.357E+06 244.3±124.2* 12 29 49 12 0.592 22.8 2.682E+06 4.532E+06 264.6± 62.5* 13 2 35 16 0.057 12.2 1.388E+05 2.428E+06 26.0± 18.9 14 0 0 8 0.000 0.0 O.OOOE+OO O.OOOE+OO O.o± 0.0 15 3 10 25 0.300 2.2 1.332E+05 4.440E+05 135.5± 89.3 80 310 7.4 3.779E+05 1.464 E+06 Area of basic unit = 9.009E-07 cm-2 CHI SQUARED = 48.83725 WITH 14 DEGREES OF FREEDOM; FAIL P(chi squared) = 0.0 % CORRELATION COEFFICIENT = 0.564 V ARIANCE OF SQR(Ns) = 2.943743 VARIANCE OF SQR(Ni) = 8.373639 Ns/Ni = 0.258 ± 0.032 MEAN RATIO = 0.197 ± 0.061 POOLED AGE = 116.7 ± 15.1 Ma MEAN AGE = 89.2 ± 27.6 Ma Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.608E+06cm-2; ND = 5868 *- Anomalous single-grain age reported here, but not in recalculated age NU8R (next page). The stratigraphic age of the deposit is Cretaceous and because paleotemperatures exceeded 225°C (from VR) after that time these fission track ages are impossibly old. GMC Data Report No. 219 6/10 7/10 GMC Data Report No. 219 Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.608E+06cm-2; ND = 5868 CHI SQUARED = 5.416492 WITH 11 DEGREES OF FREEDOM; PASS P(chi squared) = 90.9 % CORRELATION COEFFICIENT = 0.959 VARIANCE OF SQR(Ns) = 1.072261 VARIANCE OF SQR(Ni) = 8.953177 Ns/Ni = 0.106 ± 0.023 MEAN RATIO = 0.096 ± 0.033 POOLED AGE = 48.2 ± 10.7 Ma MEAN AGE = 43.6 ± 15.3 Ma Area of basic unit = 9.009E-07 cm-2 No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 1 7 5 0.143 7.8 2.220E+05 1.554E+06 64 .9± 69.4 2 1 3 5 0.333 3.3 2.220E+05 6.660E+05 150.4±173.7 3 0 1 4 0.000 1.4 O.OOOE+oo 2.775E+05 O.o± 0.0 4 0 5 16 0.000 1.7 O.OOOE+oo 3.469E+OS O.o± 0.0 5 1 9 40 0.111 1.3 2.775E+04 2.498E+05 50.5± 53.3 6 6 60 8 0.100 41.8 8.325E+05 8.325E+06 45.S± 19.5 7 0 0 32 0.000 0.0 O.OOOE+oo O.OOOE+oo O.o± 0.0 8 0 1 9 0.000 0.6 O.OOOE+oo 1.233E+05 O.o± 0.0 9 9 86 30 0.105 16.0 3.330E+05 3. 182E+06 47.6± 16.7 10 2 35 16 0.057 12.2 1.388E+OS 2.428E+06 26.0± 18.9 11 0 0 8 0.000 0.0 O.OOOE+oo O.OOOE+oo O.o± 0.0 12 3 10 25 0.300 2.2 1.332E+05 4.440E+05 135.5± 89.3 23 217 6.1 1.289E+05 1.217E+06 NU8R APATITE -7000' TO -7500' (average -2210m) NULATO WELL (Recaculated from NU8) NUIO APATITE 9000-9500' (average -2819m) NULATO WELL IRRADIATION LUI07-1; COUN1ED BY: JM No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 2 17 16 0.118 6.6 1.388E+05 1.179E+06 48.o± 35.9 2 17 6.6 1.388E+05 1.179E+06 Area of basic unit = 9.009E-07 cm-2 CHI SQUARED = 0 WITH 0 DEGREES OF FREEDOM; PASS P( chi squared) = 100.0 % CORRELA nON COEFFICIENT = 0.000 VARIANCE OF SQR(Ns) = 0 VARIANCE OF SQR(Ni) = 0 Ns/Ni = 0.118 ± 0.088 MEAN RATIO = 0.118 ± 0.000 POOLED AGE = 48,0 ± 35.9 Ma MEAN AGE = 48.0 ± 1.5 Ma Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.338E+06cm-2; ND = 8424 GMC Data Report No. 219 8/10 9/10 GMC Data Report No. 219 NU12 APATITE 11,000-11,500' (average -3429m) NULA TO WELL IRRADIATION LUI07-2; COUNTED BY: JM No. Ns Ni Na RATIO U(ppm) RHOs RHOi F.T.AGE(Ma) 1 17 58 40 0.293 9.0 4.718E+05 1.610E+06 118.8± 33.0 2 0 1 40 0.000 0.2 O. OOOE +00 2.775E+04 O.o± 0.0 3 12 72 12 0.167 37.3 1.11 OE+06 6.660E+06 67.8± 21.3 4 0 0 10 0.000 0.0 O.OOOE+OO O.OooE+OO O.o± 0.0 5 0 2 24 0.000 0.5 O.OOOE+OO 9.250E+04 O.o± 0.0 6 1 5 50 0.200 0.6 2.220E+04 1.11 OE+05 81.3± 89.1 7 0 3 16 0.000 1.2 O.OOOE+OO 2.081E+05 O.o± 0.0 8 1 3 20 0.333 0.9 5.550E+04 1.665E+05 135.0±155.9 9 1 13 25 0.077 3.2 4.440E+04 5.772E+05 31.4± 32.6 10 0 0 9 0.000 0.0 O.OOOE+OO O.OOOE+OO O.o± 0.0 11 1 11 9 0.091 7.6 1.233E+05 1.357E+06 37.1± 38.8 12 7 25 9 0.280 17.3 8.633E+05 3.083E+06 113.6± 48.7 13 8 52 60 0.154 5.4 1.480E+05 9.620E+05 62.6± 23.9 14 0 3 21 0.000 0.9 O.OOOE+OO 1.586E+05 O.o± 0.0 15 1 7 25 0.143 1.7 4.440E+04 3.108E+05 58.2± 62.2 16 0 4 12 0.000 2.1 O.OOOE+OO 3.700E+05 O.o± 0.0 49 259 4.2 1.424E+05 7.526E+05 Area of basic unit = 9.oo9E-07 cm-2 CHI SQUARED = 7.972058 WITH 15 DEGREES OF FREEDOM; PASS P(chi squared) = 92.5 % CORRELATION COEFFICIENT = 0.936 V ARIANCE OF SQR(Ns) = 1.907443 V ARIANCE OF SQR(Ni) = 6.963639 Ns/Ni = 0.189 ± 0.029 MEAN RATIO = 0.109 ± 0.030 POOLED AGE = 76.9 ± 12.2 Ma MEAN AGE = 44.3 ± 12.2 Ma: low uramium Ages calculated using a zeta of 350 ± 10 for SRM612 glass RHO D = 2.338E+06cm-2; ND = 8424 Q ~ () t:1 ~ .-1" ~ ?;j (t) Þ-d o :4 Z o N I--" \.0 Table 1. COIÚined track length data for samples from Nula10 Benedum Well. Sample # No. Tracks Track Length Qass Interval (microns) Mean Track Euor of S.D. of Mean Total (6 -1) (7 - 8) (8 - 9) (9 - 10) (10 - 11) (11- 12) (12 - 13) (13 - 14) (14 - 15) (15 - 16) (16 -11) Length (microns) Measurement (2-Sigma) NU2 17 1 0 0 0 1 0 2 3 1 7 2 14.12 na 2.62 N4 0 N8 5 0 0 0 1 1 0 0 0 9.92 0.93 3.72 NUI0 0 NU12 4 0 0 0 0 0 0 1 0 13.16 0.91 1.82 Þ---" o - Þ---" C>