Chronology of seafloor massive sulfides formation within the Pobeda hydrothermal cluster (Mid-Atlantic Ridge)

V. Kuznetsov; G. Cherkashov; K. Kuksa; A. Firstova; F. Maksimov; V. Bel’Tenev; L. Lazareva; S. Levchenko; N. Baranova

doi:10.2478/geochr-2020-0019

Figures & Tables

Sketch map of Pobeda sulfide cluster. A – Position of the Pobeda cluster at the Mid-Atlantic Ridge. B – Bathymetric map showing locations of the three fields on an eastern flank of a rift valley. C – Detailed scheme with the sampling stations locations.

Textural relationships of the major sulfide minerals. A – Porous massive pyrite ores. B – Chalcopyrite and sphalerite intergrowths and late pyrite infilling interstitial space. C – Chalcopyrite replaced by late covellite and early pyrite. D – Abundant non-sulfide minerals in the interstitial space of massive sulfide samples. E – Zonal texture around the conduit: sphalerite-pyrite (Py-1) overgrown by fine-grained pyrite (Py-2) showing close to simultaneous precipitation. Py – pyrite, Po – pyrrhotite, Cpy – chalcopyrite, Sph – sphalerite, Cv – covellite, Chl – chlorite, Tlc – talc.

230Th/U age vs 234U-specific activity for ore samples of the Pobeda sulfide cluster.

The ages of massive sulfides at Pobeda-1 and Pobeda-2 hydrothermal fields.

Mineralogical composition of massive sulfides from the Pobeda-1 and -2 hydrothermal fields (XRD analysis)_

№ field	№ sample	Minerals, (%)
	195-2	Pyrite (77.8), marcasite (19.5), aragonite (<1)
	195-3	Pyrite (91.8), marcasite (5.2), goethite (3.1)
	196-1-1	Pyrite (>99)
	196-1	Pyrite (63), marcasite (31), aragonite (<5)
Pobeda-1	196-2	Pyrite (75.7), marcasite (21.2), pyrrhotite (2.6),
		chalcopyrite (<1)
	196-3	Pyrite (95), goethite (5)
	204-2-1	Pyrite (99)
	204-3	Pyrite (99.8)
	107-4	Chalcopyrite (50), sphalerite (25), pyrite (25)
	107-8	Pyrite (87.9), marcasite (9.5), calcite (<1)
	107-10-1	Pyrite (99.0), quartz (<1)
Pobeda-2
	107-11-1	Pyrite (81.1), sphalerite (10.3), chalcopyrite (2.8), covellite (2.5), calcite (2.5)
	107-11-2	Pyrite (>99)
	245-3	Pyrite (89.9), marcasite (9.6)

The age of massive sulfide from Pobeda hydrothermal cluster_

№ sample		Age, kyr

	Pobeda-1
195-2*		22.1±1.2
195-3*		14.6±0.7
196-1		0.33±0.08
196-1-1		0.27±0.13
196-2		0.28±0.10
196-3*		6.5±0.3
204-2-1		52.0±4.0
204-3*		51.4±3.4

	Pobeda-2

107-4		37.2±8.1
107-8		4.3±0,7
107-10-1		107.0±10.0
107-11-1		4.81±0.17
107-11-2		4.96±0.18
245-3		8.59±0.41

Results of the radiochemical analyses and 230Th/U ages (both 1 sigma) of the sulfide samples from the Pobeda hydrothermal cluster_

	²³⁸U	²³⁴U	²³⁰Th	²³²Th
№ sample					²³⁰Th/²³⁴U	²³⁴U/²³⁸U	Age, kyr
		dpm/g dpm – decays per minute per gram, bdl – below detection limit

			Pobeda-1
195-2 – radioisotope data and age of massive sulfide samples from Gablina et al. 2018.	10.787±0.371	12.232±0.412	2.266±0.083	bdl	0.185±0.009	1.134±0.031	22.1±1.2
195-3 – radioisotope data and age of massive sulfide samples from Gablina et al. 2018.	30.767±0.587	35.059±0.663	4.436±0.163	bdl	0.127±0.005	1.140±0.010	14.6±0.7
196-1	9.660±0.252	10.909±0.279	0.033±0.008	bdl	0.003±0.001	1.129±0.023	0.33±0.08
196-1-1	8.113±0.216	9.033±0.236	0.022±0.011	bdl	0.002±0.001	1.113±0.024	0.27±0.13
196-2	5.511±0.133	6.373±0.149	0.017±0.006	bdl	0.003±0.001	1.156±0.025	0.28±0.10
196-3 – radioisotope data and age of massive sulfide samples from Gablina et al. 2018.	38.093±0.970	42.665±1.079	2.480±0.075	bdl	0.058±0.002	1.120±0.014	6.5±0.3
204-2-1	3.615±0.124	4.099±0.136	1.584±0.076	bdl	0.387±0.023	1.134±0.036	52.0±4.0
204-3 – radioisotope data and age of massive sulfide samples from Gablina et al. 2018.	3.409±0.153	4.419±0.185	1.695±0.046	bdl	0.384±0.019	1.296±0.058	51.4±3.4

			Pobeda-2

107-4	0.134±0.011	0.175±0.013	0.051±0.008	bdl	0.294±0.051	1.302±0.135	37.2±8.1
107-8	4.119±0.186	5.085±0.214	0.198±0.029	0.035±0.015	0.039±0.006	1.235±0.067	4.30±0.68
107-10-1	7.643±0.240	8.727±0.269	5.562±0.236	bdl	0.637±0.033	1.142±0.025	107.0±10.0
107-11-1	113.800±2.635	130.525±3.014	5.668±0.138	bdl	0.043±0.001	1.147±0.007	4.81±0.17
107-11-2	79.639±1.710	91.650±1.961	4.102±0.114	bdl	0.045±0.002	1.151±0.008	4.96±0.18
245-3	10.072±0.248	11.585±0.279	0.883±0.035	bdl	0.076±0.004	1.150±0.021	8.59±0.41

Chronology of seafloor massive sulfides formation within the Pobeda hydrothermal cluster (Mid-Atlantic Ridge)

Figures & Tables

Fig 1

Fig 2

Fig 3

Fig 4

Mineralogical composition of massive sulfides from the Pobeda-1 and -2 hydrothermal fields (XRD analysis)_

The age of massive sulfide from Pobeda hydrothermal cluster_

Results of the radiochemical analyses and 230Th/U ages (both 1 sigma) of the sulfide samples from the Pobeda hydrothermal cluster_

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