40Ar/39Ar and cosmic ray exposure ages of plagioclase-rich lithic fragments from Apollo 17 regolith, 78461

Das, J. P.; Baldwin, S. L.; Delano, J. W.

doi:10.1186/s40623-016-0381-9

Earth, Planets and Space

Table 2 Ar isotope data, cosmic ray exposure ages, ⁴⁰Ar/³⁹Ar ages for individual plagioclase-rich lithic fragments from Apollo 17, 78461 sample

From: ⁴⁰Ar/³⁹Ar and cosmic ray exposure ages of plagioclase-rich lithic fragments from Apollo 17 regolith, 78461

Sample	³⁶Ar_m	³⁷Ar_m	³⁸Ar_m	³⁹Ar_m	⁴⁰Ar_m	³⁸Ar_c ^a	P₃₈ ^sf	P₃₈ ^avg	T₃₈ ^sf	T₃₈ ^avg	⁴⁰Ar*	⁴⁰Ar*/³⁹Ar_K	Age (Ga)	⁴⁰Ar*/³⁹Ar_K	Age (Ga)
Sample	(10⁻⁶ cm³ STP/g)					³⁸Ar_c ^a	P₃₈ ^sf	P₃₈ ^avg	(Ma)	(Ma)	(%)	(⁴⁰Ar/³⁶Ar)_t = 0.146		(⁴⁰Ar/³⁶Ar)_t = 0.0
Plag#1	0.8598	2.0115	0.2047	0.0252	8.8056	4.28	0.77	0.17	5.55	25.21	99	367.44	4.27	372.69	4.30
	± 0.0015	± 0.0072	± 0.0004	± 0.0005	± 0.0044	4.28	0.77	0.17	± 0.83	3.78	99	6.24	± 0.05	6.25	± 0.04
Plag#3	1.0202	2.1366	0.3207	0.0140	4.6721	12.9	0.75	0.16	17.27	78.16	97	364.99	4.26	376.87	4.32
Plag#3	0.0019	0.0095	0.0006	0.0003	0.0028	12.9	0.75	0.16	2.59	11.72	97	6.66	0.05	6.66	0.05
Plag#6	2.4610	1.5909	0.5121	0.0218	8.3324	4.92	0.73	0.16	6.75	30.69	96	388.51	4.37	405.82	4.44
Plag#6	0.0044	0.0090	0.0013	0.0008	0.0050	4.92	0.73	0.16	1.01	4.60	96	13.89	0.07	14.87	0.07
Plag#9	1.7646	1.9960	0.4568	0.0285	10.7986	12.5	0.76	0.17	16.33	74.24	98	391.73	4.38	401.19	4.42
Plag#9	0.0031	0.0072	0.0009	0.0004	0.0077	12.5	0.76	0.17	2.45	11.14	98	2.49	0.04	2.59	0.04
Plag#10	4.0690	1.9384	0.9513	0.0084	4.5744	18.6	0.77	0.17	24.20	109.47	87	578.00	5.03	663.19	5.26
Plag#10	0.0072	0.0068	0.0021	0.0002	0.0030	18.6	0.77	0.17	3.63	16.42	87	17.89	0.06	18.30	0.06
Plag#14	3.4637	2.0183	0.7720	0.0069	2.1377	12.1	0.76	0.17	15.82	71.55	76	303.48	3.96	396.18	4.40
Plag#14	0.0065	0.0074	0.0017	0.0001	0.0018	12.1	0.76	0.17	2.37	10.73		10.56	0.07	10.77	0.06
Plag#21	0.5082	1.2445	0.1361	0.0106	3.4686	4.04	0.76	0.17	5.34	24.18	98	353.29	4.21	360.92	4.25
Plag#21	0.0008	0.0041	0.0002	0.0001	0.0011	4.04	0.76	0.17	0.80	3.63	98	1.20	0.04	1.31	0.04
Plag#22	1.0221	1.8797	0.2122	0.0119	3.5167	2.00	0.78	0.17	2.57	11.77	96	323.01	4.06	337.15	4.13
Plag#22	0.0016	0.0063	0.0004	0.0001	0.0013	2.00	0.78	0.17	0.39	1.77	96	1.78	0.04	1.86	0.04
Plag#23	0.4147	1.6445	0.2482	0.0190	6.4346	17.0	0.79	0.17	21.53	97.48	99	359.57	4.24	362.95	4.25
Plag#23	0.0007	0.0055	0.0004	0.0002	0.0012	17.0	0.79	0.17	3.23	14.62	99	1.45	0.04	1.58	0.04
Plag#24	0.9031	1.3672	0.1915	0.0284	9.5823	2.14	0.76	0.17	2.81	12.79	99	346.31	4.18	351.08	4.20
Plag#24	0.0014	0.0048	0.0003	0.0003	0.0020	2.14	0.76	0.17	0.42	1.92	99	1.29	0.04	1.65	0.04
Plag#25	2.2802	1.6158	0.4375	0.0154	5.5328	0.87	0.78	0.17	1.11	5.05	94	369.07	4.28	392.43	4.38
Plag#25	0.0037	0.0056	0.0008	0.0002	0.0017	0.87	0.78	0.17	0.17	0.73	94	2.12	0.04	2.40	0.04

The subscript m indicates that the measured abundance of Ar isotopes are corrected for blank contribution and mass discrimination. The subscript c indicates cosmogenic abundance determined by subtracting trapped component from the measured abundance of ³⁸Ar. Please see the text for details. ⁴⁰Ar*/³⁹Ar_K and ⁴⁰Ar/³⁹Ar ages are given for two different methods (described in text) used for determining radiogenic ⁴⁰Ar in the fragments. To determine the ratio ⁴⁰Ar*/³⁹Ar_K, measured ⁴⁰Ar abundance is corrected for blank contribution, mass discrimination, and non-radiogenic trapped ⁴⁰Ar (i.e., solar wind-implanted ⁴⁰Ar) while measured ³⁹Ar is corrected for blank contribution, mass discrimination, and corrected for reactor-produced ³⁹Ar from ³⁹K. ³⁸Ar production rates are in units of 10⁻⁸ cm³ STP/g/Ma
sf production rate calculated assuming lithic fragments were exposed to cosmic rays on lunar surface, avg production rate calculated based on average of production rates at the depth from 1 to 6 cm (corresponding shielding depth from 2 to 10 g/cm²)
*Percentage of radiogenic component in measured ⁴⁰Ar when corrected for trapped contribution (i.e., (⁴⁰Ar/³⁶Ar)_t = 0.146)
^aUnits of (10⁻⁸ cm³ STP/g)

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