Two-Stage Exhumation of Ultrahigh-Pressure Metamorphic Rocks from the Western Dabie Orogen, Central China

2011 ◽  
Vol 119 (1) ◽  
pp. 15-31 ◽  
Author(s):  
Yuanbao Wu ◽  
Shan Gao ◽  
Xiaochi Liu ◽  
Jing Wang ◽  
Min Peng ◽  
...  
Keyword(s):  
Central China ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Two Stage ◽  
Dabie Orogen

scholarly journals Magmatism and related metamorphism as a response to mountain-root collapse of the Dabie orogen: Constraints from geochronology and petrogeochemistry of metadiorites

2021 ◽  
Author(s):  
Yang Yang ◽  
Yi-Can Liu ◽  
Yang Li ◽  
C. Groppo ◽  
F. Rolfo
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Central China ◽  
Ultrahigh Pressure ◽  
Ca 125 ◽  
Two Stage ◽  
Dabie Orogen ◽  
Isotopic Analyses ◽  
T Values

Post-collisional mountain-root collapse and subsequent massive partial melting occurred in the high-temperature (HT) ultrahigh-pressure (UHP) metamorphic terrane of the North Dabie complex zone (NDZ), central China. The NDZ was deeply subducted in the Triassic, producing widespread migmatites and various magmatic intrusions in the Cretaceous. Post-collisional metadiorites with distinctive large K-feldspar augen porphyroblasts, locally reported but rarely exposed in the NDZ, underwent a complex evolutional history. In this contribution, integrated studies including field investigation, petrographic observation and mineral analysis, zircon U-Pb geochronological and Hf isotopic analyses, and whole-rock elemental and Sr-Nd-Pb isotopic analyses of the metadiorites were carried out. Our results provide new constraints on the mountain-root collapse in the Dabie orogen. The metadiorites are enriched in large ion lithophile elements and light rare earth elements, whereas they are depleted in high field strength elements and heavy rare earth elements with significant Ba positive anomalies, a composition consistent with the lower continental crust. All the studied samples have moderately enriched initial 87Sr/86Sr ratios (0.707582−0.708099), low εNd(t) values (−15.3 to −20.4), and low initial Pb isotopic ratios (16.0978−16.8452, 15.3167−15.4544, and 37.1778−37.8397 for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, respectively). However, they have highly negative εHf(t) values and Paleoproterozoic two-stage Hf model ages, which are only partially consistent with data from the associated UHP metamorphic rocks. Such features suggest the metadiorites resulted from a magma produced by mixing of Triassic UHP mafic lithologies and minor amounts of mantle-derived materials. Zircon morphological analysis and U-Pb sensitive high-resolution ion microprobe dating combined with conventional thermobarometry indicate that these upwelling melts crystallized at pressure-temperature (P-T) conditions of 5.4−5.7 kbar and 750−768 °C at ca. 130 Ma and subsequently suffered HT metamorphism at ca. 125 Ma. We conclude that the metadiorites’ precursors were derived from partial melting of the Triassic subducted Neoproterozoic mafic lower-crustal rocks, with addition of minor amounts of mantle-derived materials in the Early Cretaceous, in response to mountain-root collapse of the orogen. Based on petrographic textures and mineral compositions, it is moreover inferred that formation of the distinctive K-feldspar porphyroblasts is likely related to a two-stage process, i.e., crystallization derived from biotite breakdown after the formation of the metadiorite at T = 640−703 °C and P < 4.5 kbar and coarsening related to shear deformation.

Ultrahigh-pressure eclogite transformed from mafic granulite in the Dabie orogen, east-central China

2007 ◽  
Vol 25 (9) ◽  
pp. 975-989 ◽  
Author(s):  
Y.-C. LIU ◽  
S.-G. LI ◽  
X.-F. GU ◽  
S.-T. XU ◽  
G.-B. CHEN
Keyword(s):  
Central China ◽  
Mafic Granulite ◽  
Ultrahigh Pressure ◽  
Dabie Orogen ◽  
East Central

Sm/Nd, Rb/Sr, and40Ar/39Ar Isotopic Systematics of the Ultrahigh-Pressure Metamorphic Rocks in the Dabie-Sulu Belt, Central China: A Retrospective View

1999 ◽  
Vol 41 (12) ◽  
pp. 1114-1124 ◽  
Author(s):  
Shuguang Li ◽  
Emil Jagoutz ◽  
Ching-Hua Lo ◽  
Yizhi Chen ◽  
Qiuli Li ◽  
...  
Keyword(s):  
Central China ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Retrospective View
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