TY - JOUR
T1 - The timing of migmatization in the northern Arabian–Nubian Shield
T2 - Evidence for a juvenile sedimentary component in collision-related batholiths
AU - Elisha, Bar
AU - Katzir, Yaron
AU - Kylander-Clark, Andrew R.C.
AU - Golan, Tzahi
AU - Coble, Matthew A.
N1 - Funding Information:
Israel Science Foundation, Grant/Award Number: 1219/13; Israel's Ministry of National Infrastructure, Energy and Water Resources, Grant/Award Number: 215-01-023; United States-Israel Binational Science Foundation, Grant/Award Number: T-2016119
Funding Information:
Thoughtful and constructive reviews by R. Holder and M. Whitehouse and editorial work by M. Brown and D. Robinson significantly improved this paper. This study was funded by Israel Science Foundation (ISF) grant 1219/ 13 to Y. Katzir, Israel Ministry of National Infrastructures, Energy and Water Resources scholarship 215‐01‐023 to Bar Elisha, and Prof. R. Rahamimoff travel grant for young scientists of the United States Israel Binational Science Foundation (BSF) #T‐2016119 to B. Elisha. We thank Y. Eyal for sharing his rock samples with us, B. Langford for field assistance and photomicrographs and O. Dvir for his assistance in the electron microprobe work.
Publisher Copyright:
© 2019 John Wiley & Sons Ltd
PY - 2019/6/1
Y1 - 2019/6/1
N2 - Collision-related granitoid batholiths, like those of the Hercynian and Himalayan orogens, are mostly fed by magma derived from metasedimentary sources. However, in the late Neoproterozoic calcalkaline (CA) batholiths of the Arabian–Nubian Shield (ANS), which constitutes the northern half of the East African orogen, any sedimentary contribution is obscured by the juvenile character of the crust and the scarcity of migmatites. Here, we use paired in situ LASS-ICP-MS measurements of U–Th–Pb isotope ratios and REE contents of monazite and xenotime and SHRIMP-RG analyses of separated zircon to demonstrate direct linkage between migmatites and granites in the northernmost ANS. Our results indicate a single prolonged period of monazite growth at 640–600 Ma, in metapelites, migmatites and peraluminous granites of three metamorphic suites: Abu-Barqa (SW Jordan), Roded (S Israel) and Taba–Nuweiba (Sinai, Egypt). The distribution of monazite dates and age zoning in single monazite grains in migmatites suggest that peak thermal conditions, involving partial melting, prevailed for c. 10 Ma, from 620 to 610 Ma. REE abundances in monazite are well correlated with age, recording garnet growth and garnet breakdown in association with the prograde and retrograde stages of the melting reactions, respectively. Xenotime dates cluster at 600–580 Ma, recording retrogression to greenschist facies conditions as garnet continued to destabilize. Phase equilibrium modelling and mineral thermobarometry yield P–T conditions of ~650–680°C and 5–7 kbar, consistent with either water-fluxed or muscovite-breakdown melting. The expected melt production is 8–10 vol.%, allowing a melt connectivity network to form leading to melt segregation and extraction. U–Pb ages of zircon rims from leucosomes indicate crystallization of melt at 610 ± 10 Ma, coinciding with the emplacement of a vast volume of CA granites throughout the northern ANS, which were previously considered post-collisional. Similar monazite ages (c. 620 Ma) retrieved from the amphibolite facies Elat schist indicate that migmatites are the result of widespread regional rather than local contact metamorphism, representing the climax of the East African orogenesis.
AB - Collision-related granitoid batholiths, like those of the Hercynian and Himalayan orogens, are mostly fed by magma derived from metasedimentary sources. However, in the late Neoproterozoic calcalkaline (CA) batholiths of the Arabian–Nubian Shield (ANS), which constitutes the northern half of the East African orogen, any sedimentary contribution is obscured by the juvenile character of the crust and the scarcity of migmatites. Here, we use paired in situ LASS-ICP-MS measurements of U–Th–Pb isotope ratios and REE contents of monazite and xenotime and SHRIMP-RG analyses of separated zircon to demonstrate direct linkage between migmatites and granites in the northernmost ANS. Our results indicate a single prolonged period of monazite growth at 640–600 Ma, in metapelites, migmatites and peraluminous granites of three metamorphic suites: Abu-Barqa (SW Jordan), Roded (S Israel) and Taba–Nuweiba (Sinai, Egypt). The distribution of monazite dates and age zoning in single monazite grains in migmatites suggest that peak thermal conditions, involving partial melting, prevailed for c. 10 Ma, from 620 to 610 Ma. REE abundances in monazite are well correlated with age, recording garnet growth and garnet breakdown in association with the prograde and retrograde stages of the melting reactions, respectively. Xenotime dates cluster at 600–580 Ma, recording retrogression to greenschist facies conditions as garnet continued to destabilize. Phase equilibrium modelling and mineral thermobarometry yield P–T conditions of ~650–680°C and 5–7 kbar, consistent with either water-fluxed or muscovite-breakdown melting. The expected melt production is 8–10 vol.%, allowing a melt connectivity network to form leading to melt segregation and extraction. U–Pb ages of zircon rims from leucosomes indicate crystallization of melt at 610 ± 10 Ma, coinciding with the emplacement of a vast volume of CA granites throughout the northern ANS, which were previously considered post-collisional. Similar monazite ages (c. 620 Ma) retrieved from the amphibolite facies Elat schist indicate that migmatites are the result of widespread regional rather than local contact metamorphism, representing the climax of the East African orogenesis.
KW - Arabian–Nubian Shield
KW - migmatites
KW - monazite–xenotime–zircon petrochronology
KW - syn-collisional batholiths
UR - http://www.scopus.com/inward/record.url?scp=85063567466&partnerID=8YFLogxK
U2 - 10.1111/jmg.12472
DO - 10.1111/jmg.12472
M3 - Article
AN - SCOPUS:85063567466
SN - 0263-4929
VL - 37
SP - 591
EP - 610
JO - Journal of Metamorphic Geology
JF - Journal of Metamorphic Geology
IS - 5
ER -