Citation:

j.epsl.2008.12.034

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Abstract:

IODP Site U1309 was drilled at Atlantis Massif, an oceanic core complex, at 30°N on the Mid-Atlantic Ridge (MAR). We present the results of a bulk rock geochemical study (major and trace elements) carried out on 228 samples representative of the different lithologies sampled at this location.

Over 96% of Hole U1309D is made up of gabbroic rocks. Diabases and basalts cross-cut the upper part of the section; they have depleted MORB compositions similar to basalts sampled at MAR 30°N. Relics of mantle were recovered at shallow depth. Mantle peridotites show petrographic and geochemical evidence of extensive melt-rock interactions. Gabbroic rocks comprise: olivine-rich troctolites (> 70% modal olivine) and troctolites having high Mg# (82-89), high Ni (up to 2300 ppm) and depleted trace element compositions (Yb 0.06-0.8 ppm); olivine gabbros and gabbros (including gabbronorites) with Mg# of 60-86 and low trace element contents (Yb 0.125-2.5 ppm); and oxide gabbros and leucocratic dykes with low Mg# (< 50), low Ni (~65 ppm) and high trace element contents (Yb up to 26 ppm). Troctolites and gabbros are amongst the most primitive and depleted oceanic gabbroic rocks. The main geochemical characteristics of Site U1309 gabbroic rocks are consistent with a formation as a cumulate sequence after a common parental MORB melt, although (lack of systematic) downhole variations indicate that the gabbroic series were built by multiple magma injections. In detail, textural and geochemical variations in olivine-rich troctolites and gabbronorites suggest chemical interaction (assimilation?) between the parental melt and the intruded lithosphere.

Site U1309 gabbroic rocks do not represent the complementary magmatic product of 30°N volcanics, although they sample the same mantle source. The bulk trace element composition of Site U1309 gabbroic rocks is similar to primitive MORB melt compositions; this implies that there was no large scale removal of melts from this gabbro section. The occurrence of such a large magmatic sequence implies that a high magmatic activity is associated with the formation of Atlantis Massif. Our results suggest that almost all melts feeding this magmatic system stays trapped into the intruded lithosphere.

Project(s):

Integrated Ocean Drilling Program / International Ocean Discovery Program (IODP)

Coverage:

Median Latitude: 30.112926 * Median Longitude: -42.079333 * South-bound Latitude: 30.001667 * West-bound Longitude: -42.119000 * North-bound Latitude: 30.168650 * East-bound Longitude: -42.000000

Minimum DEPTH, sediment/rock: 2.07 m * Maximum DEPTH, sediment/rock: 1377.60 m

Event(s):

304-U1309B * Latitude: 30.168460 * Longitude: -42.119000 * Elevation: -1642.3 m * Recovery: 46.73 m * Campaign: (Oceanic Core Complex Formation, Atlantis Massive 1) * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 20 cores; 101.8 m cored; 45.9 % recovered; 0 m drilled; 101.8 m penetrated

304-U1309D * Latitude: 30.168650 * Longitude: -42.119000 * Elevation: -1644.9 m * Recovery: 243.69 m * Campaign: (Oceanic Core Complex Formation, Atlantis Massive 1) * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 77 cores; 380.7 m cored; 64 % recovered; 20.5 m drilled; 401.3 m penetrated

305-U1309D * Latitude: 30.001667 * Longitude: -42.000000 * Elevation: -1644.9 m * Recovery: 799.65 m * Campaign: (Oceanic Core Complex Formation, Atlantis Massive 2) * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 216 cores; 1014.2 m cored; 78.8 % recovered; 0 m drilled; 1415.5 m penetrated

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator	Method/Device	Comment
1	Event label	Event
2	DEPTH, sediment/rock	Depth sed	m			Geocode
3	Sample code/label	Sample label		Godard, Marguerite	DSDP/ODP/IODP sample designation
4	Sample code/label 2	Sample label 2		Godard, Marguerite		Piece
5	Lithologic unit/sequence	Unit		Godard, Marguerite
6	Rock type	Rock		Godard, Marguerite
7	Lithology/composition/facies	Lithology		Godard, Marguerite
8	Comment	Comment		Godard, Marguerite		Geochemistry group
9	Comment 2 (continued)	Comm 2		Godard, Marguerite
10	Method comment	Method comm		Godard, Marguerite		Lab. A: University Montpellier 2 (France) analyses carried out on (1) a quadrupole VG-PQ2 ICP-MS and (2) a ThermoFinnigan Element2 High Resolution ICP-MS; Lab. B: University of Tokyo (Japan) analyses carried out as two different batches (noted 1 & 2); Lab. C : University of Bergen (Norway); Lab. D: Pierre Sue CEA-CNRS Laboratory (France); Lab. E : Washington State University (USA); Lab. F: University of Jena (Germany); Lab. G: Max-Planck-Institute for Chemistry (Mainz, Germany).; ALL: Average of analyses from the seven different laboratories
11	Sample comment	Sample comment		Godard, Marguerite		Duplicates, Sample code
12	Lithium	Li	mg/kg	Godard, Marguerite
13	Cadmium	Cd	mg/kg	Godard, Marguerite
14	Scandium	Sc	mg/kg	Godard, Marguerite
15	Titanium	Ti	mg/kg	Godard, Marguerite
16	Vanadium	V	mg/kg	Godard, Marguerite
17	Chromium	Cr	mg/kg	Godard, Marguerite
18	Nickel	Ni	mg/kg	Godard, Marguerite
19	Copper	Cu	mg/kg	Godard, Marguerite
20	Zinc	Zn	mg/kg	Godard, Marguerite
21	Rubidium	Rb	mg/kg	Godard, Marguerite
22	Strontium	Sr	mg/kg	Godard, Marguerite
23	Lutetium	Lu	mg/kg	Godard, Marguerite
24	Zirconium	Zr	mg/kg	Godard, Marguerite
25	Niobium	Nb	mg/kg	Godard, Marguerite
26	Caesium	Cs	mg/kg	Godard, Marguerite
27	Barium	Ba	mg/kg	Godard, Marguerite
28	Lanthanum	La	mg/kg	Godard, Marguerite
29	Cerium	Ce	mg/kg	Godard, Marguerite
30	Praseodymium	Pr	mg/kg	Godard, Marguerite
31	Neodymium	Nd	mg/kg	Godard, Marguerite
32	Samarium	Sm	mg/kg	Godard, Marguerite
33	Europium	Eu	mg/kg	Godard, Marguerite
34	Gadolinium	Gd	mg/kg	Godard, Marguerite
35	Terbium	Tb	mg/kg	Godard, Marguerite
36	Dysprosium	Dy	mg/kg	Godard, Marguerite
37	Holmium	Ho	mg/kg	Godard, Marguerite
38	Erbium	Er	mg/kg	Godard, Marguerite
39	Thulium	Tm	mg/kg	Godard, Marguerite
40	Ytterbium	Yb	mg/kg	Godard, Marguerite
41	Lutetium	Lu	mg/kg	Godard, Marguerite
42	Hafnium	Hf	mg/kg	Godard, Marguerite
43	Lead	Pb	mg/kg	Godard, Marguerite
44	Thorium	Th	mg/kg	Godard, Marguerite
45	Uranium	U	mg/kg	Godard, Marguerite

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

Size:

7995 data points

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