Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction

Details Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction

Aug 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011e%26psl.308..229d&link_type=abstract

Earth and Planetary Science Letters, Volume 308, Issue 1, p. 229-244.

Mathematics

Logic

2

Postcollisional Mafic–Ultramafic Rocks, Crust–Mantle Interaction, Zircon Hf–O Isotopes, Orogenic Sclm, Continental Subduction Zone

Scientific paper

In-situ SIMS zircon U-Pb dating and O isotope analysis as well as LA-(MC)-ICPMS zircon U-Pb dating and Lu-Hf isotope analysis were carried out for postcollisional mafic-ultramafic rocks in the Dabie orogen, China. The zircon U-Pb dating gave consistent ages of 126 ± 1 to 131 ± 1 Ma for magma crystallization. Survival of residual zircon cores is identified by CL imaging and U-Pb dating, yielding ages of 697 ± 10 and 770 ± 11 Ma that agree with protolith U-Pb ages of UHP metaigneous rocks in the Dabie orogen. The zircon Hf-O isotope compositions show systematic variations that can be categorized into three groups. Group I has the lowest δ18O values of 2.0 to 2.9‰ but the highest ɛHf(t) values of - 3.5 to - 1.0 with the youngest Hf model ages of 1.2 to 1.4 Ga. Group II displays intermediate δ18O values of 4.0 to 5.1‰ and ɛHf(t) values of - 22.5 to - 13.2 with Hf model ages of 2.0 to 2.6 Ga. Group III exhibits the highest δ18O values of 5.2 to 7.3‰ but the lowest ɛHf(t) values of - 29.1 to - 18.6 with the oldest Hf model ages of 2.4 to 3.0 Ga. The three groups of Hf-O isotope compositions correspond to a three-layer Hf-O isotope structure in the subducted continental crust, suggesting their involvement in the mantle source. Along with existing data for whole-rock Sr-Nd isotopes and trace elements, it appears that the mantle source for the postcollisional mafic-ultramafic rocks is characterized by fertile lithochemistry, the arc-like signature of trace elements, the heterogeneous enrichment of radiogenic isotopes, the differential incorporation of supracrustal materials, and the variable concentrations of water. Clearly, such a source is neither the asthenospheric mantle nor the refractory subcontinental lithospheric mantle (SCLM). It is a kind of the orogenic SCLM that would be generated by reaction of the overlying SCLM-wedge peridotite with hydrous silicate melts derived from different layers of the subducted continental crust. Therefore, the postcollisional mafic-ultramafic rocks provide a petrological record of crust-mantle interaction during the continental deep subduction. Postcollisional mafic-ultramafic rocks show crust-like geochemical features. Zircon Hf-O isotopes are comparable to different layers of subducted continental crust. Orogenic SCLM source is fertile in lithochemistry and rich in radiogenic isotopes. Orogenic SCLM formed by reaction of SCLM-wedge peridotite with crust-derived melts. Postcollsional mafic-ultramafic rocks are a snapshot of crust-mantle interaction.

Affiliated with

Also associated with

No associations

Rating

Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Zircon Hf-O isotope evidence for crust-mantle interaction during continental deep subduction will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1673232