Data Quality

The limits of detection were calculated for each standard and unknown using the Longerich method in the Iolite software. For spots, all elements with the exception of Rb and Ba the concentrations are consistently 1000 to 100 times higher than the limits of detection. For lines, all elements including Rb and Ba are well above the limits of detection however the overall higher concentration of Rb and Ba in the line data should be treated with skepticism as there are two lines whose values fall below the limits of detection, and as the transect plots show, there are definitely anomalies consistent with inclusions present in the amphibole grains. Overall though, the quality of the trace element data which was of most importance to this study is excellent in its accuracy as seen with the results of the secondary external standards. NIST 612 was chosen to be used as the primary standard because its reference values were more closely aligned with the unknown average concentrations across the board despite BHVO-2G being more strongly correlated in the high REEs specifically. Since the lower REEs were of more importance to this analysis and NIST 612 matched best, it was selected to be used for the data reduction calculations in Iolite. However, the comparisons for the other two standards used are provided here for further quality control.

Spots

Table 1: Average Limits of Detection for Standard and Unknown Spots

Element	NIST 612 (ppm)	NIST 610 (ppm)	BHVO-2G (ppm)	Amphibole Unknowns (ppm)
Ca44	18.901	19.362	49.388	48.973
Sc45	0.065	0.062	0.077	0.160
Rb85	0.158	0.157	0.188	0.397
Y89	0.045	0.003	0.009	0.011
Ba137	0.037	0.037	0.036	0.088
La139	0.004	0.004	0.006	0.011
Ce140	0.005	0.004	0.006	0.013
Pr141	0.004	0.002	0.007	0.011
Nd146	0.031	0.032	0.041	0.093
Sm147	0.029	0.024	0.008	0.065
Eu153	0.007	0.005	0.008	0.015
Gd157	0.021	0.015	0.024	0.057
Tb159	0.003	0.004	0.004	0.008
Dy163	0.012	0.011	0.021	0.036
Ho165	0.003	0.003	0.004	0.009
Er166	0.011	0.011	0.010	0.027
Tm169	0.004	0.003	0.004	0.008
Yb172	0.020	0.021	0.019	0.042
Lu175	0.004	0.004	0.004	0.009

Secondary standards: NIST 610 and BHVO-2G

Table 2: Comparison to certified reference values

Element	NIST 610 Ref value (ppm)	NIST 610 average conc (ppm)	NIST 610 recovery	BHVO-2G Ref value (ppm)	BHVO-2G average conc (ppm)	BHVO-2G recovery
Ca44	82144.00	80030.95	0.97	81430.00	77687.78	0.95
Sc45	455.00	446.76	0.98	33.00	30.75	0.93
Rb85	425.70	420.23	0.99	9.20	9.31	1.01
Y89	462.00	457.50	0.99	26.00	23.05	0.89
Ba137	452.00	438.93	0.97	131.00	125.74	0.96
La139	440.00	426.62	0.97	15.20	14.40	0.95
Ce140	453.00	444.44	0.98	37.60	35.67	0.95
Pr141	448.00	443.83	0.99	5.35	4.98	0.93
Nd146	430.00	423.16	0.98	24.50	23.02	0.94
Sm147	453.00	439.38	0.97	6.10	5.71	0.94
Eu153	447.00	433.65	0.97	2.07	1.93	0.93
Gd157	449.00	431.20	0.96	6.16	5.73	0.93
Tb159	437.00	436.93	1.00	0.92	0.87	0.94
Dy163	437.00	423.39	0.97	5.28	4.90	0.93
Ho165	449.00	436.45	0.97	0.98	0.91	0.93
Er166	455.00	436.52	0.96	2.56	2.31	0.90
Tm169	435.00	427.48	0.98	0.34	0.31	0.91
Yb172	450.00	454.49	1.01	2.01	1.92	0.95
Lu175	439.00	431.27	0.98	0.28	0.26	0.94

In the table above, it is clear that NIST 610 has the better recoveries for the spot data with most falling within 3% of the reference values. The BHVO-2G recoveries tend to fall within 5% to 7% with some outliers up to 10% deviation from the reference values.

Lines

Table 3: Average Limits of Detection for Standard and Unknown Lines

Element	NIST 612 (ppm)	NIST 610 (ppm)	BHVO-2G (ppm)	Amphibole Unknowns (ppm)
Ca44	60.044	53.645	80.653	122.71
Sc45	0.201	0.191	0.296	0.49
Rb85	0.526	0.526	0.698	1.19
Y89	0.0.15	0.020	0.020	0.03
Ba137	0.117	0.100	0.179	0.28
La139	0.013	0.011	0.015	0.03
Ce140	0.016	0.014	0.019	0.03
Pr141	0.010	0.011	0.018	0.02
Nd146	0.110	0.103	0.184	0.43
Sm147	0.081	0.065	0.089	0.19
Eu153	0.022	0.021	0.029	0.05
Gd157	0.081	0.057	0.074	0.15
Tb159	0.009	0.011	0.017	0.03
Dy163	0.046	0.034	0.063	0.09
Ho165	0.009	0.009	0.015	0.03
Er166	0.049	0.036	0.044	0.07
Tm169	0.013	0.007	0.014	0.02
Yb172	0.053	0.044	0.056	0.12
Lu175	0.013	0.009	0.012	0.02

Secondary standards: NIST 610 and BHVO-2G

Table 4: Comparison to certified reference values

Element	NIST 610 Ref value (ppm)	NIST 610 average conc (ppm)	NIST 610 recovery	BHVO-2G Ref value (ppm)	BHVO-2G average conc (ppm)	BHVO-2G recovery
Ca44	82144.00	95056.28	1.16	81430.00	85783.16	1.05
Sc45	455.00	504.83	1.11	33.00	33.81	1.02
Rb85	425.70	439.63	1.03	9.20	9.01	0.98
Y89	462.00	447.98	0.97	26.00	24.69	0.95
Ba137	452.00	501.05	1.11	131.00	133.77	1.02
La139	440.00	510.83	1.16	15.20	15.74	1.04
Ce140	453.00	499.46	1.10	37.60	37.73	1.00
Pr141	448.00	452.13	1.01	5.35	5.10	0.95
Nd146	430.00	442.88	1.03	24.50	24.22	0.99
Sm147	453.00	507.09	1.12	6.10	6.12	1.00
Eu153	447.00	512.96	1.15	2.07	2.08	1.01
Gd157	449.00	453.91	1.01	6.16	5.97	0.97
Tb159	437.00	436.64	1.00	0.92	0.90	0.98
Dy163	437.00	456.22	1.04	5.28	5.16	0.98
Ho165	449.00	517.06	1.15	0.98	1.02	1.04
Er166	455.00	491.06	1.08	2.56	2.60	1.02
Tm169	435.00	428.41	0.98	0.34	0.32	0.94
Yb172	450.00	458.02	1.02	2.01	1.98	0.98
Lu175	439.00	485.68	1.11	0.28	0.28	0.99

In the table above, it is clear that NIST 610 has the better recoveries for the spot data with most falling within 10-15% of the reference values. The BHVO-2G recoveries tend to fall within 5% to 10% deviation from the reference values.

Data Quality

Spots

Lines

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