Zircon U-Pb dating and Lu-Hf isotopic analysis of metamorphic supracrustal rocks from the Ji’an Group in Tonghua area and their tectonic implications
DOI:
CSTR:
Author:
Affiliation:

Clc Number:

P597;P588.3

Fund Project:

  • Article
  • |
  • Figures
  • |
  • Metrics
  • |
  • Reference
  • |
  • Related
  • |
  • Cited by
  • |
  • Materials
  • |
  • Comments
    Abstract:

    The depositional age and provenance of meta-sedimentary rock series in the Jiao-Liao-Ji Belt remain fundamental issues of considerable debate. Using LA-MC-ICP MS zircon U-Pb dating and Lu-Hf isotope analytical techniques, representative rock samples, including metamorphic supracrustal rocks of the Ji’an Group, gneissic granite, porphyry granite and TTG gneiss from the Tonghua area in the northern part of the Belt were analyzed. The results show that the detrital zircon ages from metamorphic supracrustal rocks of the Ji’an Group present two dominant peaks of 2.5 Ga and 2.1 Ga. However, it is noteworthy that the detrital zircons from different metamorphic rock yield various age populations. The detrital zircon ages of the low grade metamorphic graphite-bearing leptynite concentrates at about 2.5 Ga, suggesting provenance of neoarchean magmatic unit. Detrital zircon in the high grade metamorphic rocks, such as sillimanite-garnet-cordierite gneiss, diopside gneiss and marble usually suffered alteration, and thus it is difficult to obtain reliable provenance age information. The metamorphic zircons from the Ji’an Group record three stages ages: 1.95~1.90 Ga, 1.90~1.85 Ga and 1.85~1.80 Ga. According to the relationship between metamorphic zircon and melting simulated by quantitative phase diagram, it is inferred that the first stage represents initial cooling timing of the metamorphic terrane, the second stage represents the timing of large-scale melt condensation and crystallization in the later cooling stage, and the third stage might be related to the tectonic exhumation, which led the terrane uplifting to the shallow crust. Zircons from metamorphic supracrustal rocks of the Ji’an Group show εHf(t) values of -12.40~+ 6.17 (mostly -8~-2). Two-stage Hf model ages vary from 3.0 to 2.3 Ga, showing similar source characteristics with Archean TTG gneiss and paleoproterozoic gneissic granite. The emplacement age of Archean amphibolite gneiss (TTG) in Tonghua area is determined as 2 574 ±11 Ma with zircon εHf(t) values ranging from +1.87 to +7.30, and two-stage Hf model ages of 2.89~2.60 Ga, indicating that the rock derived from partial melting of juvenile crust. The emplacement age of gneissic granite is dated as 2 104 ±18 Ma with zircon εHf(t) values of -2~+2, and the Hf model ages of 2.8~2.7 Ga, indicating derivation from partial melting of juvenile crust and ancient supracrustal rocks. The emplacement age of undeformed porphyritic granite is as about 1 888 ±8 Ma, the zircon εHf(t) values range from -5.43 to + 0.03, and the Hf model ages range from 2.7 to 2.5 Ga, indicating that it derived by melting of ancient supracrustal rocks. In general, the Jiao-Liao-Ji Belt presents characteristics of typical continental rift during 2.3~2.0 Ga followed by collision orogenic process during 1.95~1.85 Ga, implying that they might result from different tectonic thermal events.

    Reference
    Related
    Cited by
Get Citation

周喜文,杨崇辉,郑常青,胡大千,2022,通化地区集安群变质表壳岩锆石U-Pb定年、Lu-Hf同位素分析及其构造指示意义[J].岩石矿物学杂志,41(2):214~246. ZHOU Xi-wen, YANG Chong-hui, ZHENG Chang-qing, HU Da-qian,2022,Zircon U-Pb dating and Lu-Hf isotopic analysis of metamorphic supracrustal rocks from the Ji’an Group in Tonghua area and their tectonic implications[J]. Acta Petrologica et Mineralogica,41(2):214~246.

Copy
Share
Article Metrics
  • Abstract:
  • PDF:
  • HTML:
  • Cited by:
History
  • Received:December 01,2021
  • Revised:January 18,2022
  • Adopted:
  • Online: March 21,2022
  • Published:
Article QR Code