Remarkable Preservation of Microfossils and Biofilms in Mesoproterozoic Silicified Bitumen Concretions from Northern China

Table 1

Major and rare earth elements contents in the concretion shells and surrounding rocks.

Elements	Concretions in black shale		Surrounding black shale	Concretions in green chert		Surrounding green chert
	SC-BS-1	SC-BS-2		SC-GC-1	SC-GC-2
SiO2 (wt%)	90.10	89.03	58.53	90.70	93.26	85.90
Fe (wt%)	0.19	0.46	2.16	0.20	0.23	1.02
Ca (wt%)	0.45	0.47	0.85	0.77	0.90	0.29
Al (wt%)	0.04	0.07	4.58	0.04	0.06	3.06
La (μg/g)	0.34	0.52	30.60	0.69	0.53	13.10
Ce (μg/g)	1.14	0.52	56.80	0.29	0.08	25.80
Pr (μg/g)	0.17	0.21	7.28	0.17	0.17	3.31
Nd (μg/g)	0.93	1.11	30.80	0.59	0.65	12.80
Sm (μg/g)	0.64	0.08	5.62	0.03	0.13	2.72
Eu (μg/g)	0.13	0.12	0.85	0.05	0.04	0.47
Gd (μg/g)	0.23	0.23	4.84	0.10	0.13	2.29
Tb (μg/g)	0.03	0.18	0.88	0.07	0.10	0.40
Dy (μg/g)	0.20	0.18	5.84	0.15	0.13	2.5
Ho (μg/g)	0.03	0.04	1.14	0.03	0.03	0.52
Er (μg/g)	0.58	0.03	3.44	0.01	0.09	1.65
Tm (μg/g)	0.01	0.01	0.63	0.01	0.02	0.26
Yb (μg/g)	0.08	0.08	3.78	0.09	0.11	1.88
Lu (μg/g)	0.02	0.00	0.45	0.02	0.02	0.32
ΣREE (μg/g)	4.53	3.31	152.95	2.30	2.23	68.02
LREE (μg/g)	3.35	2.56	131.95	1.82	1.6	58.2
HREE (μg/g)	1.18	0.75	21	0.48	0.63	9.82
LREE/HREE	2.84	3.41	6.28	3.79	2.54	5.93

LREE: light rare earth elements, containing La, Ce, Pr, Nd, Sm, and Eu; HREE: heavy rare earth elements, containing Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.