An imbricate midcrustal suture zone: The mojave-yavapai province boundary in grand canyon, arizona

Mark E. Holland, K. E. Karlstrom, M. F. Doe, George E Gehrels, M. Pecha, O. P. Shufeldt, G. Begg, W. L. Griffin, Elena Belousova

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The Paleoproterozoic Mojave and Yavapai crustal provinces in southwestern Laurentia contain evolved and juvenile crust, respectively, but the nature of the province boundary remains uncertain. 1.78-1.35 Ga crystalline basement rocks of the Mojave Province preserve an evolved isotopic signature reflecting an Archean crustal component in several isotopic systems (Nd, Pb, Hf). However, no Archean rocks have been found, and hence the origin and tectonic significance of this Archean component are also unclear. This paper analyzes the U-Pb age and Hf isotopic composition of zircons from both the oldest granodiorite plutons (1.84-1.71 Ga) and the oldest metasedimentary rocks (1.75 Ga Vishnu Schist) across a 180-km-long cross-strike transect in Grand Canyon. This transect crosses the Crystal shear zone, which has been proposed as the location of a suture separating the provinces. Our results show that the characteristically bimodal population of detrital zircons in the Vishnu Schist (2.5 Ga and 1.8 Ga modes) yields mixed εHf(t) values, primarily between +5 to -5, that are uniform across the transect. Another new finding is that the 1.84 Ga Elves Chasm pluton, on which the Vishnu Schist was deposited, yields juvenile εHf(t) values of +5 to +12 and was not the dominant source for the ca. 1.85 Ga peak in the 1.75 Ga Vishnu Schist. Instead, the Vishnu Schist was derived from an Archean craton mixed with intermediate to evolved 1.85 Ga crust. Metasediments show no evidence in support of the proposed suture. Paradoxically, plutons east and west of the Crystal shear zone do support models for a crustal suture. Plutons east of the Crystal shear zone dated at 1.74-1.71 Ga yield juvenile εHf(t) values of +5 to +12 that are characteristic of the Yavapai Province. Plutons west of the Crystal shear zone show juvenile to evolved Paleoproterozoic grains (εHf(t) of -5 to +10) as well as xenocrystic Archean and 1.85 Ga grains (εHf(t) of -12 to +10). These data support the proposition that the Crystal shear zone marks a sharp boundary between the Mojave and Yavapai crustal provinces. However, the overlapping Vishnu Schist suggests a more complicated crustal architecture. The depositional setting of the Vishnu Schist remains unclear; however, we interpret the ultimate geometry of the transect to reflect an ~200-km-wide middle-crustal duplex system in which the 1.75 Ga Vishnu Schist was deposited across both Mojave and Yavapai crust. This system was subsequently imbricated in an accretionary complex. The ultimate architecture is of a distributed boundary with slivers of plutons that carry the isotopic signature of their respective provinces imbricated within metasediments.

Original languageEnglish (US)
Pages (from-to)1391-1410
Number of pages20
JournalBulletin of the Geological Society of America
Volume127
Issue number9-10
DOIs
StatePublished - 2015

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suture zone
schist
canyon
pluton
shear zone
Archean
crystal
transect
metasediment
crust
zircon
province
duplex
Laurentia
crystalline rock
metasedimentary rock
basement rock
granodiorite
craton
isotopic composition

ASJC Scopus subject areas

  • Geology

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An imbricate midcrustal suture zone : The mojave-yavapai province boundary in grand canyon, arizona. / Holland, Mark E.; Karlstrom, K. E.; Doe, M. F.; Gehrels, George E; Pecha, M.; Shufeldt, O. P.; Begg, G.; Griffin, W. L.; Belousova, Elena.

In: Bulletin of the Geological Society of America, Vol. 127, No. 9-10, 2015, p. 1391-1410.

Research output: Contribution to journalArticle

Holland, ME, Karlstrom, KE, Doe, MF, Gehrels, GE, Pecha, M, Shufeldt, OP, Begg, G, Griffin, WL & Belousova, E 2015, 'An imbricate midcrustal suture zone: The mojave-yavapai province boundary in grand canyon, arizona', Bulletin of the Geological Society of America, vol. 127, no. 9-10, pp. 1391-1410. https://doi.org/10.1130/B31232.1
Holland, Mark E. ; Karlstrom, K. E. ; Doe, M. F. ; Gehrels, George E ; Pecha, M. ; Shufeldt, O. P. ; Begg, G. ; Griffin, W. L. ; Belousova, Elena. / An imbricate midcrustal suture zone : The mojave-yavapai province boundary in grand canyon, arizona. In: Bulletin of the Geological Society of America. 2015 ; Vol. 127, No. 9-10. pp. 1391-1410.
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T1 - An imbricate midcrustal suture zone

T2 - The mojave-yavapai province boundary in grand canyon, arizona

AU - Holland, Mark E.

AU - Karlstrom, K. E.

AU - Doe, M. F.

AU - Gehrels, George E

AU - Pecha, M.

AU - Shufeldt, O. P.

AU - Begg, G.

AU - Griffin, W. L.

AU - Belousova, Elena

PY - 2015

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N2 - The Paleoproterozoic Mojave and Yavapai crustal provinces in southwestern Laurentia contain evolved and juvenile crust, respectively, but the nature of the province boundary remains uncertain. 1.78-1.35 Ga crystalline basement rocks of the Mojave Province preserve an evolved isotopic signature reflecting an Archean crustal component in several isotopic systems (Nd, Pb, Hf). However, no Archean rocks have been found, and hence the origin and tectonic significance of this Archean component are also unclear. This paper analyzes the U-Pb age and Hf isotopic composition of zircons from both the oldest granodiorite plutons (1.84-1.71 Ga) and the oldest metasedimentary rocks (1.75 Ga Vishnu Schist) across a 180-km-long cross-strike transect in Grand Canyon. This transect crosses the Crystal shear zone, which has been proposed as the location of a suture separating the provinces. Our results show that the characteristically bimodal population of detrital zircons in the Vishnu Schist (2.5 Ga and 1.8 Ga modes) yields mixed εHf(t) values, primarily between +5 to -5, that are uniform across the transect. Another new finding is that the 1.84 Ga Elves Chasm pluton, on which the Vishnu Schist was deposited, yields juvenile εHf(t) values of +5 to +12 and was not the dominant source for the ca. 1.85 Ga peak in the 1.75 Ga Vishnu Schist. Instead, the Vishnu Schist was derived from an Archean craton mixed with intermediate to evolved 1.85 Ga crust. Metasediments show no evidence in support of the proposed suture. Paradoxically, plutons east and west of the Crystal shear zone do support models for a crustal suture. Plutons east of the Crystal shear zone dated at 1.74-1.71 Ga yield juvenile εHf(t) values of +5 to +12 that are characteristic of the Yavapai Province. Plutons west of the Crystal shear zone show juvenile to evolved Paleoproterozoic grains (εHf(t) of -5 to +10) as well as xenocrystic Archean and 1.85 Ga grains (εHf(t) of -12 to +10). These data support the proposition that the Crystal shear zone marks a sharp boundary between the Mojave and Yavapai crustal provinces. However, the overlapping Vishnu Schist suggests a more complicated crustal architecture. The depositional setting of the Vishnu Schist remains unclear; however, we interpret the ultimate geometry of the transect to reflect an ~200-km-wide middle-crustal duplex system in which the 1.75 Ga Vishnu Schist was deposited across both Mojave and Yavapai crust. This system was subsequently imbricated in an accretionary complex. The ultimate architecture is of a distributed boundary with slivers of plutons that carry the isotopic signature of their respective provinces imbricated within metasediments.

AB - The Paleoproterozoic Mojave and Yavapai crustal provinces in southwestern Laurentia contain evolved and juvenile crust, respectively, but the nature of the province boundary remains uncertain. 1.78-1.35 Ga crystalline basement rocks of the Mojave Province preserve an evolved isotopic signature reflecting an Archean crustal component in several isotopic systems (Nd, Pb, Hf). However, no Archean rocks have been found, and hence the origin and tectonic significance of this Archean component are also unclear. This paper analyzes the U-Pb age and Hf isotopic composition of zircons from both the oldest granodiorite plutons (1.84-1.71 Ga) and the oldest metasedimentary rocks (1.75 Ga Vishnu Schist) across a 180-km-long cross-strike transect in Grand Canyon. This transect crosses the Crystal shear zone, which has been proposed as the location of a suture separating the provinces. Our results show that the characteristically bimodal population of detrital zircons in the Vishnu Schist (2.5 Ga and 1.8 Ga modes) yields mixed εHf(t) values, primarily between +5 to -5, that are uniform across the transect. Another new finding is that the 1.84 Ga Elves Chasm pluton, on which the Vishnu Schist was deposited, yields juvenile εHf(t) values of +5 to +12 and was not the dominant source for the ca. 1.85 Ga peak in the 1.75 Ga Vishnu Schist. Instead, the Vishnu Schist was derived from an Archean craton mixed with intermediate to evolved 1.85 Ga crust. Metasediments show no evidence in support of the proposed suture. Paradoxically, plutons east and west of the Crystal shear zone do support models for a crustal suture. Plutons east of the Crystal shear zone dated at 1.74-1.71 Ga yield juvenile εHf(t) values of +5 to +12 that are characteristic of the Yavapai Province. Plutons west of the Crystal shear zone show juvenile to evolved Paleoproterozoic grains (εHf(t) of -5 to +10) as well as xenocrystic Archean and 1.85 Ga grains (εHf(t) of -12 to +10). These data support the proposition that the Crystal shear zone marks a sharp boundary between the Mojave and Yavapai crustal provinces. However, the overlapping Vishnu Schist suggests a more complicated crustal architecture. The depositional setting of the Vishnu Schist remains unclear; however, we interpret the ultimate geometry of the transect to reflect an ~200-km-wide middle-crustal duplex system in which the 1.75 Ga Vishnu Schist was deposited across both Mojave and Yavapai crust. This system was subsequently imbricated in an accretionary complex. The ultimate architecture is of a distributed boundary with slivers of plutons that carry the isotopic signature of their respective provinces imbricated within metasediments.

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