Transtensional opening of the North Atlantic ocean characterized by magnetic fabric of the Kerforne doleritic dyke (Brittany, France)

2 p

Transtensional opening of the North Atlantic ocean characterized by magnetic fabric of the Kerforne doleritic dyke (Brittany, France)

2 p

Systematic Changes in Lead Isotopic Composition with Soil Age in Glacial Granitic Terrains

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155812/1/Harlavan_et_al_1998_Systematic_changes.pd

Lead isotope systematics of granitoid weathering

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155787/1/Erel_et_al_1994_Lead_isotope.pd

The coupled release of REE and Pb to the soil labile pool with time by weathering of accessory phases, Wind River Mountains, WY

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155685/1/Harlavan_et_al_2009_Coupled_release.pd

UPb dating of Fe-rich phases using a sequential leaching method

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155802/1/Erel_et_al_1997_U-Pb_dating.pd

Long-distance transport of North Gondwana Cambro-Ordovician sandstones : evidence from detrital zircon Hf isotopic composition

A voluminous Early Paleozoic sequence of quartz-rich sandstones was deposited in northern Gondwana following its assembly during the Neoproterozoic-Cambrian Pan-African Orogeny. Field evidence for the sense of transport indicate that sediments were carried from Gondwana hinterland towards the supercontinent margins in the North (present coordinates). Derivation from Pan-African terranes is evident from the ubiquity of detrital zircons with Neoproterozoic U-Pb ages, but the exact provenance of these siliciclastic deposits remains unclear. Herein we present new Hf isotopic data from U-Pb dated detrital zircons of the Cambro-Ordovician sandstone that top the juvenile Neoproterozoic basement of the Arabian-Nubian Shield in Israel and Jordan. Remarkably, the detrital zircon Hf isotopic signal stands in marked contrast with Nd and Hf isotopic signature of the underlying basement. A preponderance (61%) of the Neoproterozoic-aged detrital zircons from the Cambro-Ordovician sandstones in Israel and Jordan yielded negative epsilon (super Hf(t) ) values incompatible with a juvenile source. Therefore, rather than from the adjacent Arabian-Nubian Shield, most of the detrital zircons were derived from distant terrane(s), comprising pre-Neoproterozoic crust reworked during Pan-African orogeny. Because our sampling sites are situated at the northern tip of the Arabian-Nubian Shield, sand must have been transported several thousand kilometers before deposition. This finding also implies that the Arabian-Nubian Shield and other Pan-African orogens of NE Africa were completely warned down by the onset of Cambro-Ordovician deposition and that vast areas in the northern part of Gondwana wer e then low-lying such as to allow transfer of sand across the continent.1 page(s

Crustal evolution and recycling in the northern Arabian-Nubian Shield : new perspectives from zircon Lu-Hf and U-Pb systematics

This paper presents laser-ablation (MC)-ICP-MS single-zircon Hf isotopic data coupled with U-Pb geochronology from a unique rock inventory in southern Israel, recording ca. 300m.y. of Neoproterozoic crustal evolution in the northern Arabian-Nubian Shield (ANS). The early, island-arc magmatic cycle in this area is recorded by detrital zircons from arc-derived metasediments, dated between 870 and 760Ma, and by ca. 790 and 740Ma orthogneisses. Zircon e{open}Hf(t) values from these rocks are all positive, supporting previous isotopic evidence for the overall juvenile nature of northern ANS crust. Nonetheless, detrital zircons from the metasedimentary units display a wide range of e{open}Hf(t) values between +1 and +13. The lower values in this range suggest some contribution from an older crustal component. The involvement of pre-Neoproterozoic crustal component is also indicated by the occurrence of rare zircons with pre-Neoproterozoic ages and/or negative e{open}Hf(t) values in younger (post-collisional) magmas that intrude the arc sequence. Arc accretion was followed by a period of ∼60m.y. of relative igneous tranquility interrupted only by the emplacement of local basic dike swarm at ca. 705Ma. Average zircon e{open}Hf (t) value of +10 found in one of these dikes indicates a depleted mantle source possibly implying a mid-Neoproterozoic extensional phase. The later, post-collisional magmatic cycle marks the transition of the accreted arc complexes into a mature continental crust. It consists of voluminous 680-600Ma granitoid plutons of calc-alkaline affinity, and subordinate 610-580Ma intrusions of alkaline affinity. Average zircon e{open}Hf(t) values in these post-collisional rocks are all positive and range between +6 and +9, compatible with both mantle source and juvenile crust reworking.16 page(s