Discovery of the Mesozoic Volcanic Rocks in Lahegen Area of the Eastern North Qaidam Tectonic Belt, and Its Geological Implications: Evidence from Geochemistry and Zircon Geochronology

doi:10.19657/j.geoscience.1000-8527.2023.074

Abstract

Abstract:

The stratigraphic attribution of volcanic rocks in the eastern area of the northern margin of the Qaidam Basin is difficult to determine due to a lack of geochronological data.These rocks are located between the Wahongshan-Wenquan Fault and the southern margin of the Zongwulong Mountain Fault.This also leads to significant disputes over the division of geotectonic units in this area, as no Mesozoic volcanic rocks have been found here before.In this study, a set of Mesozoic volcanic rocks consisting of rhyolite, intermediate-acid brecciate lava and dacite was newly confirmed in the Lahegen area.Zircon U-Pb dating was performed on the rhyolite samples using the LA-ICP-MS technique with weighted mean age of 248.3±1.2 Ma, indicating an Early Triassic age.The geochemical data show that the volcanic rock is a metaluminous high-potassium calc-alkaline rock with clear fractionation of light rare earth elements, enrichment of light rare earth elements and depletion of heavy rare earth elements.The mean δEu value is 0.63, indicating a weak negative anomaly.The rocks are relatively enriched in large ion lithophile elements (e.g., Rb and Ba) and high field strength elements (e.g.,Th, U, Pb, and Zr), and are significantly depleted in Sr, Ta, and Nb.These are typical geochemical characteristics of continental island arc volcanic rocks.Zircon Hf isotope compositions show ε_Hf(t) values of~-19.62 to-3.07 and $t D M 2$ values of~1,639 Ma to 2,421 Ma, indicating that the volcanic rocks are derived from the partial melting of Paleoproterozoic crustal materials.Based on geochronology and geochemical characteristics, the volcanic rocks are attributed to the anatexis of crustal materials (the Darken Daban Group) caused by the northward subduction of the Anemaqen Ocean to the East Kunlun block in the Early Triassic.The volcanic rocks of the Hongshuichuan Formation are similar to those in the magma arc of Olashan, according to the regional correlation.Therefore, these rocks are identified as Early Triassic Hongshuichuan Formation volcanic rocks.The confirmation of the studied volcanic rocks indicates that the Lahegen area has a close tectonic affinity with the Olashan magmatic arc of the East Kunlun orogenic belt.This study provides new evidence for the tectonic division of the eastern area of the northern margin of Qaidam Basin.

Key words: Lahegen area, volcanic rock, zircon U-Pb dating, Hf isotope, tectonic environment

CLC Number:

ZHENG Ying, HAN Jie, ZHANG Xiaoyong, GOU Mingliang, WANG Ming, YUAN Bowu. Discovery of the Mesozoic Volcanic Rocks in Lahegen Area of the Eastern North Qaidam Tectonic Belt, and Its Geological Implications: Evidence from Geochemistry and Zircon Geochronology[J]. Geoscience, 2024, 38(04): 1147-1161.

Figures/Tables 18

Fig.1 Geotectonic location map of the Lahegen area in the eastern section of the northern margin of the Qaidam Basin (revised by Wang et al[21])

Fig.2 Geological sketch of the Lahegen area in the eastern section of the northern margin of the Qaidam Basin

Fig.3 Histogram of the Hongshuichuan Formation in the Lahegen area

Fig.4 Macroscopic and microscopic structure photos of volcanic rocks in the Lahegen area

Table 1 LA-ICP-MS zircon U-Pb age data of volcanic rocks in the Lahegen area

测点	含量(10^-6)			U/Th	同位素比值						年龄(Ma)
测点	Th	Pb	U	U/Th	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ
1	180	15.3	385	2.30	0.0511	0.0013	0.2754	0.0070	0.0390	0.0005	246.1	60.5	247.0	5.6	246.9	3.3
2	332	19.2	461	1.46	0.0520	0.0013	0.2818	0.0070	0.0392	0.0004	287.6	58.5	252.1	5.5	248.4	2.9
3	1327	42.0	1103	0.93	0.0518	0.0012	0.2847	0.0063	0.0397	0.0006	279.4	53.6	254.4	5.0	251.0	4.1
4	356	23.9	589	1.73	0.0501	0.0015	0.2752	0.0088	0.0396	0.0006	203.4	69.3	246.8	7.0	250.5	4.0
5	558	27.7	672	1.37	0.0512	0.0008	0.2784	0.0049	0.0392	0.0004	252.4	36.6	249.4	3.9	248.3	2.5
6	298	16.5	381	1.39	0.0506	0.0008	0.2885	0.0048	0.0411	0.0003	224.4	37.4	257.3	3.8	260.2	2.3
7	685	25.0	615	0.99	0.0516	0.0008	0.2803	0.0054	0.0393	0.0005	270.4	38.5	250.9	4.3	248.6	3.5
8	828	38.3	942	1.22	0.0513	0.0006	0.2767	0.0039	0.0389	0.0003	258.3	31.1	248.0	3.1	246.1	2.2
9	1410	34.5	878	0.67	0.1079	0.0027	0.5920	0.0151	0.0395	0.0005	1765.9	46.9	472.1	9.6	250.2	3.2
10	116	6.01	140	1.30	0.0527	0.0015	0.2926	0.0080	0.0406	0.0004	319.5	68.3	260.6	6.3	257.0	2.7
11	459	22.9	535	1.29	0.0604	0.0020	0.3266	0.0099	0.0389	0.0004	619.1	72.4	287.0	7.6	246.1	2.9
12	721	29.4	712	1.05	0.0509	0.0007	0.2769	0.0042	0.0392	0.0003	239.9	33.8	248.2	3.4	248.2	2.0
13	391	23.8	522	1.41	0.0505	0.0011	0.2952	0.0064	0.0422	0.0003	218.4	50.9	262.7	5.0	267.0	2.4
14	1117	44.1	1110	1.07	0.0592	0.0009	0.3204	0.0057	0.0390	0.0003	575.7	34.2	282.2	4.3	247.0	2.4
15	742	28.9	698	0.99	0.0514	0.0010	0.3001	0.0075	0.0422	0.0006	260.9	48.7	266.5	5.9	266.4	3.7
16	393	23.7	585	1.59	0.0511	0.0008	0.2766	0.0045	0.0392	0.0003	247.6	37.2	248.0	3.6	248.2	2.3
17	861	38.0	944	1.19	0.0545	0.0007	0.2932	0.0043	0.0390	0.0004	395.5	32.0	261.1	3.3	246.8	2.8
18	390	19.2	463	1.25	0.0520	0.0012	0.2938	0.0061	0.0411	0.0005	285.9	52.8	261.6	4.8	260.1	3.1
19	259	17.3	425	1.85	0.0508	0.0010	0.2758	0.0055	0.0394	0.0004	232.0	46.7	247.3	4.4	249.1	2.6
20	338	21.4	523	1.64	0.0518	0.0008	0.2814	0.0045	0.0395	0.0004	278.3	38.7	251.8	3.5	250.3	2.6
21	765	25.7	671	0.99	0.0538	0.0018	0.2955	0.0101	0.0400	0.0008	363.2	77.5	262.9	7.9	253.1	5.2
22	240	18.2	432	1.92	0.0511	0.0015	0.2766	0.0093	0.0391	0.0005	247.7	70.8	248.0	7.4	247.3	3.7
23	307	19.7	484	1.67	0.0514	0.0007	0.2770	0.0041	0.0390	0.0003	262.3	32.3	248.3	3.2	247.0	2.0
24	554	28.7	696	1.35	0.0511	0.0006	0.2758	0.0041	0.0391	0.0003	247.6	30.4	247.3	3.2	247.3	2.0
25	533	23.2	581	1.15	0.0517	0.0007	0.2811	0.0053	0.0392	0.0004	276.5	34.2	251.5	4.2	248.1	2.7
26	216	16.3	431	2.09	0.0518	0.0029	0.2836	0.0160	0.0397	0.0008	277.0	131.452	253.5	12.6	250.9	5.4
27	234	17.1	394	1.79	0.0521	0.0014	0.2850	0.0083	0.0397	0.0004	289.8	64.0	254.6	6.5	251.5	3.0
28	455	25.3	597	1.42	0.0522	0.0011	0.2985	0.0069	0.0414	0.0005	298.2	51.9	265.2	5.4	261.7	3.4
29	379	21.8	537	1.53	0.0511	0.0008	0.2759	0.0049	0.0391	0.0003	246.3	39.3	247.4	3.9	247.7	2.4
30	542	28.4	669	1.32	0.0517	0.0011	0.2791	0.0060	0.0390	0.0004	275.7	51.4	249.9	4.8	247.1	2.5

Table 1 LA-ICP-MS zircon U-Pb age data of volcanic rocks in the Lahegen area

测点	含量(10^-6)			U/Th	同位素比值						年龄(Ma)
测点	Th	Pb	U	U/Th	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ
1	180	15.3	385	2.30	0.0511	0.0013	0.2754	0.0070	0.0390	0.0005	246.1	60.5	247.0	5.6	246.9	3.3
2	332	19.2	461	1.46	0.0520	0.0013	0.2818	0.0070	0.0392	0.0004	287.6	58.5	252.1	5.5	248.4	2.9
3	1327	42.0	1103	0.93	0.0518	0.0012	0.2847	0.0063	0.0397	0.0006	279.4	53.6	254.4	5.0	251.0	4.1
4	356	23.9	589	1.73	0.0501	0.0015	0.2752	0.0088	0.0396	0.0006	203.4	69.3	246.8	7.0	250.5	4.0
5	558	27.7	672	1.37	0.0512	0.0008	0.2784	0.0049	0.0392	0.0004	252.4	36.6	249.4	3.9	248.3	2.5
6	298	16.5	381	1.39	0.0506	0.0008	0.2885	0.0048	0.0411	0.0003	224.4	37.4	257.3	3.8	260.2	2.3
7	685	25.0	615	0.99	0.0516	0.0008	0.2803	0.0054	0.0393	0.0005	270.4	38.5	250.9	4.3	248.6	3.5
8	828	38.3	942	1.22	0.0513	0.0006	0.2767	0.0039	0.0389	0.0003	258.3	31.1	248.0	3.1	246.1	2.2
9	1410	34.5	878	0.67	0.1079	0.0027	0.5920	0.0151	0.0395	0.0005	1765.9	46.9	472.1	9.6	250.2	3.2
10	116	6.01	140	1.30	0.0527	0.0015	0.2926	0.0080	0.0406	0.0004	319.5	68.3	260.6	6.3	257.0	2.7
11	459	22.9	535	1.29	0.0604	0.0020	0.3266	0.0099	0.0389	0.0004	619.1	72.4	287.0	7.6	246.1	2.9
12	721	29.4	712	1.05	0.0509	0.0007	0.2769	0.0042	0.0392	0.0003	239.9	33.8	248.2	3.4	248.2	2.0
13	391	23.8	522	1.41	0.0505	0.0011	0.2952	0.0064	0.0422	0.0003	218.4	50.9	262.7	5.0	267.0	2.4
14	1117	44.1	1110	1.07	0.0592	0.0009	0.3204	0.0057	0.0390	0.0003	575.7	34.2	282.2	4.3	247.0	2.4
15	742	28.9	698	0.99	0.0514	0.0010	0.3001	0.0075	0.0422	0.0006	260.9	48.7	266.5	5.9	266.4	3.7
16	393	23.7	585	1.59	0.0511	0.0008	0.2766	0.0045	0.0392	0.0003	247.6	37.2	248.0	3.6	248.2	2.3
17	861	38.0	944	1.19	0.0545	0.0007	0.2932	0.0043	0.0390	0.0004	395.5	32.0	261.1	3.3	246.8	2.8
18	390	19.2	463	1.25	0.0520	0.0012	0.2938	0.0061	0.0411	0.0005	285.9	52.8	261.6	4.8	260.1	3.1
19	259	17.3	425	1.85	0.0508	0.0010	0.2758	0.0055	0.0394	0.0004	232.0	46.7	247.3	4.4	249.1	2.6
20	338	21.4	523	1.64	0.0518	0.0008	0.2814	0.0045	0.0395	0.0004	278.3	38.7	251.8	3.5	250.3	2.6
21	765	25.7	671	0.99	0.0538	0.0018	0.2955	0.0101	0.0400	0.0008	363.2	77.5	262.9	7.9	253.1	5.2
22	240	18.2	432	1.92	0.0511	0.0015	0.2766	0.0093	0.0391	0.0005	247.7	70.8	248.0	7.4	247.3	3.7
23	307	19.7	484	1.67	0.0514	0.0007	0.2770	0.0041	0.0390	0.0003	262.3	32.3	248.3	3.2	247.0	2.0
24	554	28.7	696	1.35	0.0511	0.0006	0.2758	0.0041	0.0391	0.0003	247.6	30.4	247.3	3.2	247.3	2.0
25	533	23.2	581	1.15	0.0517	0.0007	0.2811	0.0053	0.0392	0.0004	276.5	34.2	251.5	4.2	248.1	2.7
26	216	16.3	431	2.09	0.0518	0.0029	0.2836	0.0160	0.0397	0.0008	277.0	131.452	253.5	12.6	250.9	5.4
27	234	17.1	394	1.79	0.0521	0.0014	0.2850	0.0083	0.0397	0.0004	289.8	64.0	254.6	6.5	251.5	3.0
28	455	25.3	597	1.42	0.0522	0.0011	0.2985	0.0069	0.0414	0.0005	298.2	51.9	265.2	5.4	261.7	3.4
29	379	21.8	537	1.53	0.0511	0.0008	0.2759	0.0049	0.0391	0.0003	246.3	39.3	247.4	3.9	247.7	2.4
30	542	28.4	669	1.32	0.0517	0.0011	0.2791	0.0060	0.0390	0.0004	275.7	51.4	249.9	4.8	247.1	2.5

Fig.5 Representative magmatic zircon CL images and U-Pb ages of volcanic rocks from the Lahegen area

Fig.6 Concordia diagram (a) and weighted mean 206Pb/238U age (b) for volcanic rocks in the Lahegen area

Table 2 Zircon Hf isotope analysis of volcanic rocks in the Lahegen area

点号	t(Ma)	¹⁷⁶Yb/¹⁷⁷Hf	¹⁷⁶Lu/¹⁷⁷Hf	¹⁷⁶Hf/¹⁷⁷Hf	ε_Hf(t)	$t D M 1$ (Ma)	$t D M C$ (Ma)	f_Lu/Hf
QU-Pb6136-01	246.98	0.05810	0.00155	0.28236	-9.31	1276	1865	-0.95
QU-Pb6136-02	248.48	0.07484	0.00192	0.28233	-10.49	1335	1941	-0.94
QU-Pb6136-03	251.07	0.11061	0.00277	0.28211	-18.15	1680	2421	-0.92
QU-Pb6136-04	250.50	0.05769	0.00153	0.28237	-8.86	1260	1840	-0.95
QU-Pb6136-05	248.35	0.04056	0.00105	0.28240	-7.62	1196	1761	-0.97
QU-Pb6136-07	248.67	0.09112	0.00237	0.28216	-16.59	1599	2322	-0.93
QU-Pb6136-08	246.13	0.07300	0.00189	0.28235	-9.82	1305	1897	-0.94
QU-Pb6136-12	248.23	0.04455	0.00119	0.28246	-5.69	1123	1639	-0.96
QU-Pb6136-16	248.24	0.05674	0.00145	0.28239	-8.22	1230	1798	-0.96
QU-Pb6136-19	249.17	0.05458	0.00142	0.28234	-9.96	1300	1908	-0.96
QU-Pb6136-20	250.34	0.05323	0.00137	0.28239	-7.93	1219	1781	-0.96
QU-Pb6136-21	253.17	0.09889	0.00250	0.28216	-16.28	1594	2306	-0.92
QU-Pb6136-22	247.33	0.04190	0.00110	0.28245	-5.97	1131	1656	-0.97
QU-Pb6136-23	247.09	0.05232	0.00138	0.28235	-9.46	1277	1875	-0.96
QU-Pb6136-24	247.30	0.06711	0.00175	0.28228	-12.11	1394	2041	-0.95

Table 2 Zircon Hf isotope analysis of volcanic rocks in the Lahegen area

点号	t(Ma)	¹⁷⁶Yb/¹⁷⁷Hf	¹⁷⁶Lu/¹⁷⁷Hf	¹⁷⁶Hf/¹⁷⁷Hf	ε_Hf(t)	$t D M 1$ (Ma)	$t D M C$ (Ma)	f_Lu/Hf
QU-Pb6136-01	246.98	0.05810	0.00155	0.28236	-9.31	1276	1865	-0.95
QU-Pb6136-02	248.48	0.07484	0.00192	0.28233	-10.49	1335	1941	-0.94
QU-Pb6136-03	251.07	0.11061	0.00277	0.28211	-18.15	1680	2421	-0.92
QU-Pb6136-04	250.50	0.05769	0.00153	0.28237	-8.86	1260	1840	-0.95
QU-Pb6136-05	248.35	0.04056	0.00105	0.28240	-7.62	1196	1761	-0.97
QU-Pb6136-07	248.67	0.09112	0.00237	0.28216	-16.59	1599	2322	-0.93
QU-Pb6136-08	246.13	0.07300	0.00189	0.28235	-9.82	1305	1897	-0.94
QU-Pb6136-12	248.23	0.04455	0.00119	0.28246	-5.69	1123	1639	-0.96
QU-Pb6136-16	248.24	0.05674	0.00145	0.28239	-8.22	1230	1798	-0.96
QU-Pb6136-19	249.17	0.05458	0.00142	0.28234	-9.96	1300	1908	-0.96
QU-Pb6136-20	250.34	0.05323	0.00137	0.28239	-7.93	1219	1781	-0.96
QU-Pb6136-21	253.17	0.09889	0.00250	0.28216	-16.28	1594	2306	-0.92
QU-Pb6136-22	247.33	0.04190	0.00110	0.28245	-5.97	1131	1656	-0.97
QU-Pb6136-23	247.09	0.05232	0.00138	0.28235	-9.46	1277	1875	-0.96
QU-Pb6136-24	247.30	0.06711	0.00175	0.28228	-12.11	1394	2041	-0.95

Fig.7 Diagram of zircon εHf (t)-t of volcanic rocks in the Lahegen area

Table 3 Analytical results of major (%), trace and rare earth elements (10-6) in the volcanic rocks in the Lahegen

样品号	岩性	SiO₂		TiO₂		Al₂O₃		TFe₂O₃		FeO		MnO		MgO		CaO		Na₂O		K₂O		P₂O₅		LOI		Total		A/NK
Q6136-1	流纹岩	73.35		0.224		13.30		2.02		0.96		0.036		0.52		1.02		3.67		4.56		0.064		0.92		99.69		1.21
Q6136-2		75.95		0.069		13.12		1.32		0.58		0.051		0.41		0.27		5.04		2.87		0.016		0.70		99.80		1.15
Q6446		70.22		0.251		14.52		2.17		0.92		0.068		0.60		1.19		4.71		4.67		0.07		1.43		99.89		1.13
QPM104-54		77.25		0.06		11.80		0.54		0.47		0.03		0.18		0.69		3.07		4.93		0.02		0.77		99.35		1.14
Q140-1	中酸性角砾熔岩	73.01		0.22		13.17		2.34		1.03		0.08		0.53		0.71		3.85		4.57		0.06		0.89		99.44		1.17
Q140-2	中酸性角砾熔岩	74.70		0.20		12.63		2.27		1.06		0.07		0.48		0.50		3.63		4.51		0.06		0.50		99.56		1.16
QPM104-50	英安岩	69.41		0.35		14.52		1.33		1.68		0.05		2.55		1.59		2.98		2.36		0.08		2.81		98.03		1.94
样品号	岩性	A/ CNK		Na₂O+ K₂O		K₂O/ Na₂O		AR		R₁		R₂		SI		MF		σ		La		Ce		Pr		Nd		Sm
Q6136-1	流纹岩	1.03		8.23		1.24		3.70		2431.6		395.41		4.71		66.58		2.23		32.3		54.8		5.4		17.9		3.0
Q6136-2		1.10		7.91		0.56		3.88		2545.1		306.05		4.67		61.66		1.89		44.7		77.2		7.9		26.5		4.9
Q6446		0.96		9.38		0.99		3.96		1824.3		441.53		5.13		63.72		3.23		48.2		77.7		7.3		24.2		4.1
QPM104-54		1.01		7.99		1.60		4.55		2873.6		314.67		2.50		68.24		1.86		31.7		53.7		6.0		20.0		3.4
Q140-1	中酸性角砾熔岩	1.04		8.42		1.18		4.08		2331.7		360.88		4.53		68.62		2.36		29.0		46.9		5.1		16.2		2.7
Q140-2	中酸性角砾熔岩	1.07		8.13		1.24		4.25		2539.1		325.57		4.15		70.58		2.08		27.1		47.9		5.2		16.7		2.7
QPM104-50	英安岩	1.40		5.34		0.79		1.99		2919.9		580.95		16.37		33.24		1.08		35.8		61.6		7.1		24.2		4.0
样品号	岩性	Eu		Gd		Tb		Dy		Ho		Er		Tm		Yb		Lu		Y		Li		Be		Sc		Cr
Q6136-1	流纹岩	0.6		2.6		0.4		2.5		0.6		1.7		0.3		1.8		0.3		17.3		11.4		1.9		2.6		1.3
Q6136-2		0.7		4.4		0.8		5.2		1.3		3.9		0.6		3.9		0.6		40.5		12.6		1.9		2.2		0.7
Q6446		0.8		3.4		0.6		3.5		0.7		2.2		0.3		2.2		0.4		22.3		11.7		1.8		3.4		2.1
QPM104-54		0.6		3.0		0.5		3.0		0.6		1.8		0.4		2.4		0.3		17.2		2.7		1.5		2.4		11.0
Q140-1	中酸性角砾熔岩	0.6		2.8		0.4		2.2		0.4		1.4		0.2		1.5		0.3		14.3		9.8		1.7		2.6		-
Q140-2	中酸性角砾熔岩	0.6		2.8		0.3		2.0		0.4		1.3		0.2		1.4		0.2		13.3		10.1		1.8		2.3		-
QPM104-50	英安岩	0.9		3.5		0.6		3.4		0.7		2.0		0.4		2.5		0.4		19.4		27.9		2.0		6.6		20.9
样品号	岩性	V		Co		Ni		Cu		Zn		Sn		Ga		Rb		Sr		Zr		Nb		Cs		Ba		Hf
Q6136-1	流纹岩	12.2		2.2		0.6		1.6		30.9		1.5		14.2		138.9		127.4		135.4		9.8		2.2		729.2		3.6
Q6136-2		1.1		0.3		0.1		1.4		41.3		2.8		14.7		108.2		54.9		119.3		12.6		3.6		465.4		3.7
Q6446		14.6		2.2		0.8		1.6		38.1		1.9		15.1		119.7		115.7		153.9		10.9		2.1		744.1		4.2
QPM104-54		1.9		0.6		4.8		2.2		30.5		2.2		8.8		134.0		51.5		103.0		7.7		1.1		710.5		3.0
Q140-1	中酸性角砾熔岩	14.2		1.9		1.1		2.5		31.4		-		11.6		128.7		120.3		113.9		10.9		1.3		630.7		3.0
Q140-2	中酸性角砾熔岩	14.6		1.9		1.4		4.8		27.2		-		11.9		147.3		107.7		117.4		11.6		1.7		758.8		3.2
QPM104-50	英安岩	36.8		4.9		8.3		6.9		71.5		2.0		14.5		90.3		190.3		177.0		9.1		4.6		833.5		5.1
样品号	岩性	Ta	Tl		Pb		Th		U		REE		LREE		HREE		LREE/ HREE		δEu		δCe		Rb/Sr		(La/ Sm)_N		(Gd/ Yb)_N		(La/ Yb)_N
Q6136-1	流纹岩	0.8	0.9		19.5		17.8		3.6		124.32		114.08		10.23		11.14		0.67		0.91		1.09		6.78		1.15		11.97
Q6136-2		1.0	0.7		18.1		21.3		4.2		182.70		162.02		20.68		7.83		0.46		0.91		1.97		5.74		0.90		7.70
Q6446		0.9	0.8		16.6		20.7		3.1		175.54		162.25		13.28		12.21		0.64		0.89		1.03		7.48		1.26		14.94
QPM104-54		0.8	-		21.3		13.7		2.3		127.20		115.2		11.99		9.60		0.56		0.87		2.60		5.91		1.02		9.04
Q140-1	中酸性角砾熔岩	0.8	0.6		24.5		12.4		3.1		109.59		100.42		9.16		10.95		0.71		0.85		1.06		6.87		1.49		12.97
Q140-2	中酸性角砾熔岩	0.9	0.6		19.3		13.0		3.4		109.01		100.26		8.74		11.46		0.70		0.91		1.36		6.35		1.61		12.97
QPM104-50	英安岩	0.8	-		18.1		14.1		2.6		147.0		133.59		13.40		9.96		0.71		0.87		0.47		5.66		1.13		9.67

Table 3 Analytical results of major (%), trace and rare earth elements (10-6) in the volcanic rocks in the Lahegen

样品号	岩性	SiO₂		TiO₂		Al₂O₃		TFe₂O₃		FeO		MnO		MgO		CaO		Na₂O		K₂O		P₂O₅		LOI		Total		A/NK
Q6136-1	流纹岩	73.35		0.224		13.30		2.02		0.96		0.036		0.52		1.02		3.67		4.56		0.064		0.92		99.69		1.21
Q6136-2		75.95		0.069		13.12		1.32		0.58		0.051		0.41		0.27		5.04		2.87		0.016		0.70		99.80		1.15
Q6446		70.22		0.251		14.52		2.17		0.92		0.068		0.60		1.19		4.71		4.67		0.07		1.43		99.89		1.13
QPM104-54		77.25		0.06		11.80		0.54		0.47		0.03		0.18		0.69		3.07		4.93		0.02		0.77		99.35		1.14
Q140-1	中酸性角砾熔岩	73.01		0.22		13.17		2.34		1.03		0.08		0.53		0.71		3.85		4.57		0.06		0.89		99.44		1.17
Q140-2	中酸性角砾熔岩	74.70		0.20		12.63		2.27		1.06		0.07		0.48		0.50		3.63		4.51		0.06		0.50		99.56		1.16
QPM104-50	英安岩	69.41		0.35		14.52		1.33		1.68		0.05		2.55		1.59		2.98		2.36		0.08		2.81		98.03		1.94
样品号	岩性	A/ CNK		Na₂O+ K₂O		K₂O/ Na₂O		AR		R₁		R₂		SI		MF		σ		La		Ce		Pr		Nd		Sm
Q6136-1	流纹岩	1.03		8.23		1.24		3.70		2431.6		395.41		4.71		66.58		2.23		32.3		54.8		5.4		17.9		3.0
Q6136-2		1.10		7.91		0.56		3.88		2545.1		306.05		4.67		61.66		1.89		44.7		77.2		7.9		26.5		4.9
Q6446		0.96		9.38		0.99		3.96		1824.3		441.53		5.13		63.72		3.23		48.2		77.7		7.3		24.2		4.1
QPM104-54		1.01		7.99		1.60		4.55		2873.6		314.67		2.50		68.24		1.86		31.7		53.7		6.0		20.0		3.4
Q140-1	中酸性角砾熔岩	1.04		8.42		1.18		4.08		2331.7		360.88		4.53		68.62		2.36		29.0		46.9		5.1		16.2		2.7
Q140-2	中酸性角砾熔岩	1.07		8.13		1.24		4.25		2539.1		325.57		4.15		70.58		2.08		27.1		47.9		5.2		16.7		2.7
QPM104-50	英安岩	1.40		5.34		0.79		1.99		2919.9		580.95		16.37		33.24		1.08		35.8		61.6		7.1		24.2		4.0
样品号	岩性	Eu		Gd		Tb		Dy		Ho		Er		Tm		Yb		Lu		Y		Li		Be		Sc		Cr
Q6136-1	流纹岩	0.6		2.6		0.4		2.5		0.6		1.7		0.3		1.8		0.3		17.3		11.4		1.9		2.6		1.3
Q6136-2		0.7		4.4		0.8		5.2		1.3		3.9		0.6		3.9		0.6		40.5		12.6		1.9		2.2		0.7
Q6446		0.8		3.4		0.6		3.5		0.7		2.2		0.3		2.2		0.4		22.3		11.7		1.8		3.4		2.1
QPM104-54		0.6		3.0		0.5		3.0		0.6		1.8		0.4		2.4		0.3		17.2		2.7		1.5		2.4		11.0
Q140-1	中酸性角砾熔岩	0.6		2.8		0.4		2.2		0.4		1.4		0.2		1.5		0.3		14.3		9.8		1.7		2.6		-
Q140-2	中酸性角砾熔岩	0.6		2.8		0.3		2.0		0.4		1.3		0.2		1.4		0.2		13.3		10.1		1.8		2.3		-
QPM104-50	英安岩	0.9		3.5		0.6		3.4		0.7		2.0		0.4		2.5		0.4		19.4		27.9		2.0		6.6		20.9
样品号	岩性	V		Co		Ni		Cu		Zn		Sn		Ga		Rb		Sr		Zr		Nb		Cs		Ba		Hf
Q6136-1	流纹岩	12.2		2.2		0.6		1.6		30.9		1.5		14.2		138.9		127.4		135.4		9.8		2.2		729.2		3.6
Q6136-2		1.1		0.3		0.1		1.4		41.3		2.8		14.7		108.2		54.9		119.3		12.6		3.6		465.4		3.7
Q6446		14.6		2.2		0.8		1.6		38.1		1.9		15.1		119.7		115.7		153.9		10.9		2.1		744.1		4.2
QPM104-54		1.9		0.6		4.8		2.2		30.5		2.2		8.8		134.0		51.5		103.0		7.7		1.1		710.5		3.0
Q140-1	中酸性角砾熔岩	14.2		1.9		1.1		2.5		31.4		-		11.6		128.7		120.3		113.9		10.9		1.3		630.7		3.0
Q140-2	中酸性角砾熔岩	14.6		1.9		1.4		4.8		27.2		-		11.9		147.3		107.7		117.4		11.6		1.7		758.8		3.2
QPM104-50	英安岩	36.8		4.9		8.3		6.9		71.5		2.0		14.5		90.3		190.3		177.0		9.1		4.6		833.5		5.1
样品号	岩性	Ta	Tl		Pb		Th		U		REE		LREE		HREE		LREE/ HREE		δEu		δCe		Rb/Sr		(La/ Sm)_N		(Gd/ Yb)_N		(La/ Yb)_N
Q6136-1	流纹岩	0.8	0.9		19.5		17.8		3.6		124.32		114.08		10.23		11.14		0.67		0.91		1.09		6.78		1.15		11.97
Q6136-2		1.0	0.7		18.1		21.3		4.2		182.70		162.02		20.68		7.83		0.46		0.91		1.97		5.74		0.90		7.70
Q6446		0.9	0.8		16.6		20.7		3.1		175.54		162.25		13.28		12.21		0.64		0.89		1.03		7.48		1.26		14.94
QPM104-54		0.8	-		21.3		13.7		2.3		127.20		115.2		11.99		9.60		0.56		0.87		2.60		5.91		1.02		9.04
Q140-1	中酸性角砾熔岩	0.8	0.6		24.5		12.4		3.1		109.59		100.42		9.16		10.95		0.71		0.85		1.06		6.87		1.49		12.97
Q140-2	中酸性角砾熔岩	0.9	0.6		19.3		13.0		3.4		109.01		100.26		8.74		11.46		0.70		0.91		1.36		6.35		1.61		12.97
QPM104-50	英安岩	0.8	-		18.1		14.1		2.6		147.0		133.59		13.40		9.96		0.71		0.87		0.47		5.66		1.13		9.67

Fig.8 TAS diagram of volcanic rocks in the Lahegen area

Fig.9 AFM diagram of volcanic rocks in the Lahegen area

Fig.10 SiO2-K2O diagram of volcanic rocks in the Lahegen area

Fig.11 A/CNK-A/NK diagram of volcanic rocks in the Lahegen area

Fig.12 δEu-(La/Yb)Ndiagram of volcanic rocks in the Lahegen area

Fig.13 Chondrite-normalized rare earth element patterns (a) and primitive mantle-normalized trace element patterns of the Lahegen volcanic rocks (b)

Fig.14 Tectonic environment identification diagrams of volcanic rocks in Lahegen area(basemap after reference[37])

Fig.15 Regional stratigraphic zoning map of northern Qinghai

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