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Apatite is a common U-and Th-bearing accessory mineral in igneous and metamorphic rocks, and a minor but widespread detrital component in clastic sedimentary rocks. U-Pb and Th-Pb dating of apatite has potential application in sedimentary provenance studies, as it likely represents first cycle detritus compared to the polycyclic behaviour of zircon. However, low U, Th and radiogenic Pb concentrations, elevated common Pb and the lack of a U-Th-Pb apatite standard remain significant challenges in dating apatite by LA-ICPMS, and consequently in developing the chronometer as a provenance tool.This study has determined U-Pb and Th-Pb ages for seven well known apatite occurrences (Durango, Emerald Lake, Kovdor, Mineville, Mudtank, Otter Lake and Slyudyanka) by LA-ICPMS. Analytical procedures involved rastering a 10μm spot over a 40×40μm square to a depth of 10μm using a Geolas 193nm ArF excimer laser coupled to a Thermo ElementXR single-collector ICPMS. These raster conditions minimized laser-induced inter-element fractionation which was corrected for using the back-calculated intercept of the time-resolved signal. A Tl-U-Bi-Np tracer solution was aspirated with the sample into the plasma to correct for instrument mass bias.External standards (Plešovice and 91500 zircon, NIST SRM 610 and 612 silicate glasses and STDP5 phosphate glass) along with Kovdor apatite were analysed to monitor U-Pb, Th-Pb and Pb-Pb ratios. Age calculations employed between 11 and 33 analyses per sample and used a weighted average of the common Pb-corrected ages, a Tera-Wasserburg Concordia intercept age and a Tera-Wasserburg Concordia intercept age anchored through

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U-Pb ages were obtained on single detrital zircon grains separated from six samples of Neoproterozoic and Lower Palaeozoic sedimentary and volcanosedimentary rocks from NW Iberia using the laser ablation microprobe-inductively coupled plasma mass spectrometry (LAM-ICP-MS) method. Precambrian greywackes yielded abundant zircons with Neoproterozoic (800-640 Ma) and Mesoproterozoic (0.9-1.2 Ga) ages, and a smaller proportion of Palaeoproterozoic (1.8-2 Ga) and Archaean zircons. Palaeozoic samples (Lower Cambrian and Ordovician) yielded abundant zircons with younger Neoproterozoic (ca. 550 and 620 Ma) and Mesoproterozoic (0.9-1.2 Ga) ages. Palaeoproterozoic (1.8-2 Ga) and Archaean zircons were also found. This data set, used in conjuction with previous paleogeographic and isotopic studies sheds new light on the Precambrian-early Palaeozoic evolution of NW Iberia and is consistent with the following sequence of events: (1) Early Cadomian-Avalonian subduction and arc construction (ca. 800-640 Ma). This magmatic episode created the main arc edifice (Avalonia); (2) full development of a back arc basin upon which the Neoproterozoic sediments were deposited (ca. 640-600 Ma). The combined U-Pb ages of detrital zircons and Nd isotopic features of these sedimenary rocks suggest that they were mostly shed from the main magmatic arc. On the basis of the presence of Grenvillian age detrital zircons with short waterborne transport before incorporation in the sediment, we propose that the basin was possibly located in a peri-Amazonian realm close to West Avalonian terranes. These basins were developed upon a cratonic basement that possibly involved both Grenvillian (ca. 0.9-1.2 Ga) and Transamazonian (ca. 1.9-2.1) igneous rocks. The reported zircon ages suggest a long-lived subduction, starting at ca. 800 Ma and terminated by ca. 580-570 Ma with no geological record of a final collision event; (3) the continuation of extension gave rise to the undocking of Avalonia from the back-arc. Detrital zircon ages in Lowermost Cambrian strata suggest that the main arc edifice had drifted away by ca. 550-540 Ma and was no longer shedding detritus into the back-arc basin. (4) During the Lower Ordovician, further extension of an already thinned crust gave rise to the Lower Ordovician 'Ollo de Sapo' magmatic event (ca. 480 Ma). Coeval volcanism in neighbouring areas displaying within-plate geochemical signatures is consistent with an extensional setting for the generation of the Lower Ordovician igneous and sedimentary rocks. Detrital zircon ages and Nd