of numerous north-south trending Miocene and volcanic centres and lava flows. For

Transcription

1 DATA REPOSITORY DR Duggen et al. SAMPLES AND ANALYTICAL METHODS Lavas were collected from a ca. 10 km by 100 km volcanic field consisting of numerous north-south trending Miocene and volcanic centres and lava flows. For geochemical analyses cm diameter whole-rock chips were treated ultrasonically with de-ionised water. The dried chips were hand-picked using a binocular and then pulverised in an agate mill. Major and an array of trace elements as indicated in Table 1 were determined from fused tablets using a Philips X unique PW 1480 X-ray fluorescence spectrometer (XRF) at the IFM-GEOMAR in Kiel. International reference standards JB-, JB-3 (basalts), JA-, JA-3 (andesites), JR-, JR-3 (rhyolites), JG-, GM (granites) and JF-1 (feldspar) were analysed with the samples in order to evaluate the precision and accuracy of the measurements. H O and CO were measured photometrically with a Rosemont Infrared Photometer CSA Additional trace element concentrations were analysed by means of inductively coupled plasma-mass spectrometry (ICP-MS) at the Institute of Geosciences, University of Bremen, using a ThermoFinnigan Element. Sample powders were pressure digested in a MLS Ethos microwave with a mixture of pure HF and HNO 3 at 10 C. About 50 mg of sample was processed and the analyte solution was spiked with 1 ng/ml indium as internal standard; the final dilution was 1:5000 corresponding to 0. mg/ml of total dissolved solid. In order to avoid mass interferences, the REE and Hf were measured at high resolution (10,000), the transition metals at medium (4,000) and all other elements at low (300) resolution. Based on repeated analyses of standard reference materials the external precision is better than 5% for most elements, and is better than 7% for duplicate digestions of 1

2 samples. The accuracy of USGS standards BHVO- and BCR-, analysed along with the samples, is better than 10% except for Cs, Cr and Cu (up to 15%) with respect to the USGS reference values. The ICP-MS data is reported in Table 1. Sr-Nd isotope analyses of lavas were performed at Royal Holloway University of London (RHUL) using the clean laboratory facilities and the VG354 mass spectrometer (TIMS) of the Department of Geology. Powders were dissolved in polytetraflouroethylene (PTFE) Savillex beakers with a concentrated mixture of destilled HNO 3 and HF on a hotplate at ca. 130 ºC. For Sr-isotope analysis the powders were leached prior to digestion in the Savillex beakers with 6 M HCl on the hotplate for about 1 hour. After dissolution and conversion to nitrate, Sr was extracted and purified with two passes through small pipette-tip size columns loaded with Eichrom Sr-Spec resin. Light rare earth elements were separated from matrix elements on small columns filled with ~50 mg of TRU-Spec resin. Nd was then separated from the other rare earth elements by two passes on anion exchange columns. Sr was loaded on single Re filaments using a TaF 5 sandwich-loading technique and run multi-dynamically on the TIMS. Nd was loaded on single Refilaments with silica gel and dilute H 3 PO 4 and run multi-dynamically as NdO +. Details about the analytical procedures are reported in the literature (Thirlwall, 1991a, b). Long-term means of standards are ±14 ( s.d.) for 87 Sr/ 86 Sr (SRM 987 standard, n=0) and ±7 (Aldrich standard, n=86) for 143 Nd/ 144 Nd. The Sr- Nd isotope data of the Middle Atlas lavas along with internal errors ( s.e.) are reported in Table. Pb-isotope analyses were performed in clean laboratories at the Leibniz Institute of Marine Sciences, IFM-GEOMAR, in Kiel, using a MAT6 RPQ + TIMS. Prior to digestion handpicked mm matrix chips were leached with hot ultrapure

3 6 M HCl or M HCl (samples ATL B and 9), rinsed with water and then digested with a mixture of ultrapure HF and HNO 3. Pb was separated and purified by two passes on the AG1-X8 anion resin, loaded on Re filaments with silica gel and run in static multicollection on the TIMS. The long-term reproducibility as determined from repeated measurements of NBS 981 (N=1) is 06 Pb/ 04 Pb = ±0.007, 07 Pb/ 04 Pb = ±0.009, 08 Pb/ 04 Pb = ±0.07 and are corrected to the NBS 981 values given in (Todt et al., 1996). Total chemistry blanks were <100 pg for Pb and thus considered negligible. REFERENCES Thirlwall, M.F., 1991a, High-precision multicollector isotopic analysis of low levels of Nd as oxide: Chemical Geology (Isotope Science Section), v. 94, p. 13-., 1991b, Long-term reproducibility of multicollector Sr and Nd isotope ratio analyses: Chemical Geology (Isotope Science Section), v. 94, p Todt, W., Cliff, R.A., Hanser, A., and Hofmann, A.W., 1996, Evaluation of a 0 Pb- 05 Pb double spike for high precision lead isotope analyses, in Basu, A., and Hart, S., eds., Earth Processes: Reading the Isotopic Code, Volume 95: Washington D.C., Geophys. Monogr. Ser., AGU, p

4 Table DR1: Major and trace element data of Middle Atlas lavas and igneous rock standards Sample no. ATL B duplatl batl atl aatl eatl (a?)atl Location Ain Kahla area Ain Kahla areaain Kahla areaain Kahla area Bekrit village Ain Kahla area Ain Kahla area Rock type basanite basanite basanite picrite? basanite basanite basanite lava flow lava flow lava flow cobble cobble boulder lava flow Major elements in weight % measured by XRF SiO MgO Al O MnO Na O CaO TiO P O K O FeO total CO H O Sum Trace elements in parts per million (ppm) determined by XRF (*) and ICP-MS (#) Li * Sc * V # Cr # Co # Ni # Cu * Zn # Ga # Rb # Sr # Y # Zr # Nb * Cs * Ba # La * Ce * Pr * Nd *

5 Ta * Tl * Pb * Th * U * Dy/Yb Zr/Hf

6 Table 1 continued. Table 1 continued. Sample no. ATL ATL A ATL ATL ATL c ATL d Sample no. Location Jebel Habri Ain Kahla area Ben Said Talialite, south Ain Kahla area Jebel Hebri Location Rock type basanite basanite basanite, essent. clas basanite with mantle basanite basanite Rock type scoria agglutinate con lava flow from scoria cone xenolith from lava flow boulder huge bomb (50 cm) b Major elements in weight % measured by XRF SiO SiO MgO MgO AL O AL O 3 MnO MnO Na O Na O CaO CaO TiO TiO P O P O 5 K O K O FeO total FeO total CO CO H O H O Sum Sum Major elements in we Trace elements in parts per million (ppm) determined by XRF (*) and ICP-MS (#) Trace elements in par Li * Li * Sc * Sc * V # V # Cr # Cr # Co # Co # Ni # Ni # Cu * Cu * Zn # Zn # Ga # Ga # Rb # Rb # Sr # Sr # Y # Y # Zr # Zr # Nb * Nb * Cs * Cs * Ba # Ba # La * La * Ce * Ce * Pr * Pr * Nd * Nd *

7 Ta * Ta * Tl * Tl * Pb * Pb * Th * Th * U * U * Dy/Yb Dy/Yb Zr/Hf Zr/Hf

8 Table 1 continued. ATL e ATL ATL a ATL ATL ATL Sample no. ATL Jebel Hebri Bekrit area Gouffre S of J. Hebri 1km W of J. Hebri Talialite, northoutgui NE of El HaiebLocation Azrou, N entrance basanite basanite basanite basanite with mantle alkali basalt alkali basalt Rock type alkali basalt bomb or dike fragmen lava flow lava flow xenoliths from lava flow lava flow lava flow lava flow weight % measured by XRF Major elements in weight % measured SiO MgO AL O MnO Na O CaO TiO P O K O FeO total CO H O Sum 99.8 arts per million (ppm) determined by XRF (*) and ICP-MS (#) Trace elements in parts per million (ppm Li * Sc * V # Cr # Co # Ni # Cu * Zn # Ga # Rb # Sr # Y # Zr # Nb * Cs * Ba # La * Ce * Pr * Nd * 43.4

9 Ta * Tl * Pb * Th * U * Dy/Yb Zr/Hf 37.3

10 Table 1 continued. ATL a TZ BIR RGM MAG AGV Sample no. BCR- BCR- Jebel Hebri Oued Amlil quarry Location basalt from xenolithbasanite/hawaiite Standard Standard Standard Standard Rock type Standard Standard block in scoria cone lava flow d by XRF pm) determined by XRF (*) and ICP-MS (#) Trace elements in parts per million (ppm) determined Li * Sc * V # Cr # Co # Ni # Cu * Zn # Ga # Rb # Sr # 8.8 Y # Zr # Nb * Cs * Ba # La * Ce * Pr * Nd *

11 Ta * Tl * Pb * Th * U * Dy/Yb 44.3 Zr/Hf

12 BCR- Standard BCR- Standard d by XRF (*) and ICP-MS (#)

13

14 Table DR: Radiogenic isotope data of Middle Atlas lavas Sample no. Rock type 87 Sr/ 86 Sr s.e. 143 Nd/ 144 Nd s.e. 06 Pb/ 04 Pb s.e. 07 Pb/ 04 Pb s.e. 08 Pb/ 04 Pb s.e. ATL alkali basalt ATL basanite ATL alkali basalt ATL basanite ATL B basanite ATL basanite ATL basanite ATL d basanite ATL a basanite ATL alkali basalt ATL basanite ATL basanite TZ basanite/hawaiit