Xiaoqi Li , Yan Zhao , Wenhao Ao , Meiqian Xu , Juan Zhang
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引用次数: 0
Abstract
Investigations on the petrogenesis and geological significances of intermediate-acidic intrusions from the Houhe Complex provide crucial insights for understanding Paleoproterozoic tectonic evolution of the northern Yangtze Block. The intermediate rocks (quartz monzonite, diorite, and quartz diorite), crystallized at ∼ 2.08 Ga, exhibit high Na2O + K2O (5.94–9.47 wt%), Mg# (46.1–49.7), and elevated Cr (17.4–82.6 ppm) and Ni (11.4–29.0 ppm) concentrations, along with whole-rock ɛNd(t) and zircon εHf(t) values of –1.2 to + 1.1 and –0.5 to + 2.8, respectively, corresponding to two–stage Nd-Hf model ages of 2.8–2.5 Ga, suggesting their derivation from partial melting of ancient mafic lower crust with contributions of lithospheric mantle- and subducted slab-derived materials. The acidic rocks, comprising ∼ 2.07 Ga monzogranite (Mg# = 33.9–39.2; Cr = 9.54–18.1 ppm; Ni = 5.99–8.06 ppm) and ∼ 2.03 Ga Na-rich granite (Na2O/K2O = 7.28–15.0; Mg# = 37.6–48.2; Cr = 0.96–2.32 ppm; Ni = 4.31–5.46 ppm), exhibit whole–rock ɛNd(t) and zircon εHf(t) values of –2.1 to + 0.9 and –0.6 to + 3.0, respectively, with two-stage Nd-Hf model ages of 2.8–2.5 Ga, suggesting their origin from partial melting of Neoarchean mafic-felsic crustal materials with negligible mantle- and subducted slab contributions. Both intermediate and acidic rocks exhibit low Rb, Ta, Nb and Y concentrations, and low Nb/Zr values. Additionally, the crustal thickness calculated based on whole-rock (La/Yb)N values exceeds 60 Km at ∼ 2.0 Ga. Collectively, these findings suggest that the Paleoproterozoic (2.1–2.0 Ga) intermediate-acidic intrusions from the Houhe Complex formed in an active continental margin tectonic setting. Furthermore, integrating the temporal-spatial distribution of Paleoproterozoic rock units, especially ophiolitic mélange in the northern Yangtze Block, it is proposed that the eastern and western parts of the northern Yangtze Block possibly assembled along the Huangling–Zhongxiang subduction-collision zone at ∼ 2.0–1.9 Ga, corresponding to the global Columbia supercontinent–related orogenic events during ∼ 2.1–1.9 Ga.
期刊介绍:
Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as:
(1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology;
(2) Geochronology and isotope and elemental geochemistry;
(3) Precambrian mineral deposits;
(4) Geophysical aspects of the early Earth and Precambrian terrains;
(5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes.
In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes.
Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.