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The Study of Granitoids in Kalamaili Area of Easten Junggar, Xinjiang

Author: YangGaoXue
Tutor: LiYongJun
School: Chang'an University
Course: Structural Geology
Keywords: Sequence classification Tectonic environment Magma evolvement A type granite Kalamaili East Junggar
CLC: P588.121
Type: Master's thesis
Year: 2008
Downloads: 164
Quote: 1
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Abstract

The Kalamaili area is located to north of the Xinjiang, united position of the Xiboliya plate and the Junggar plate, that is a important part in frame of the mid-asia tectonics. That experienced two tectonics cycle in Early Paleozoic and Late Paleozoic, many times close-open, each close-open process formatted trench-arc-basin system. In this tectonics setting, more lager area intrusive rock in late Carboniferous to early Permian distributed in Kalamaili area, formatted the granite belt. This paper basid on predecessor research, the author merger granite bodies and take part sequence, difference of analysis and discuss in merger principle, evience and mostly characters, isotope ages formative tectonic setting and magma evolvement of magma sequence. Gained achievement as follows:1. Basid on materials of the predecessor and the 1∶50000 investigate achievement, the paper take part sequence about granite in Kalamaili area: Huangyangshan sequence, Beilekuduke sequence, Kubusunan sequence and Xikuangbei sequence.2. Predecessor refered Sabei granite bodies and Sujiquan granite bodies not the independent bodies, but the only part of the Huangyangshan sequence. new sequence include medium granularity biotite alkali-feldspar granite(Sujiquan granite bodies);medium granularity amphibole alkali-feldspar granite;medium granularity arfvedsonite alkali-feldspar granite;medium-fine granularity arfvedsonite alkali-feldspar granite(Sabei granite bodies);fine granularity biotite alkali-feldspar granite and fine granularity mixing granite(containing graphite).3. High-precision LA-ICP-MS zircon U-Pb dating used in the four sequence in the research area. .In Huangyangshan sequence, host rock medium granularity arfvedsonite alkali-feldspar granite and enclaves LA-ICP-MS zircon U-Pb age is 311±12Ma,306±7Ma, medium-fine granularity arfvedsonite alkali-feldspar granite is 313±2Ma, medium granularity biotite alkali-feldspar granite is 304±2Ma, medium granularity amphibole alkali-feldspar granite is 300Ma～305Ma, the ages are very consistent within errors, belongs to Late Carboniferous; Beilekuduke sequence the age is 283±9Ma; Kubusunan sequence and enclaves age is 287±2Ma and 286±3Ma; Xikuangbei sequence age is 277±11Ma. We can see the Huangyangshan sequence formatted earlier, Beilekuduke and Kubusunan sequence next, the last is Xikuangbei sequence, as a whole, the time between late Carboniferous to early Permian, belongs to magma activity scope(330～ 265Ma). High-precision LA-ICP-MS zircon U-Pb dating age,not only acquisition the reliable material, but also enrich the age of granite in the area, most important is taking stronge evdent for rebuilding tectonic framework and recovering magma evolution in east Junggar.4. Petrology and the rock geochemistry reseach indicated, the four sequence have characteristics of high silicon, rich alkali, low aluminum, high differentiation. In SiO2-AR, Huangyangshan sequence, Beilekuduke sequence and Xikuangbei sequence all demonstrated alkali-granite series, on A/NK-A/CNK that have sub-aluminum feature, and high FeOt/MgO, 10000×Ga/Al and Zr+Nb+Ce+Y, belongs to sub-aluminum A type granite and alkali-granite. But Kubusunan sequence belongs to sub-aluminum calcium-alkali granite.5. Trace and rare earth element(REE) research indicated, Kalamaili granite(the four sequence) have rich Rb, K, Th et al large ion lithophile elements(LILE) and Zr, Hf et al high filed-strength element(sHFSE), deplete Ba, Sr, Nb, Eu et al, have weak Nb-Ta trough, more strength Eu deplete, chondrite-normalized REE pattern is right-incline“sea-gull”type, curved shape is similar.6. In tectonics environment diagram of granite concluded, Huangyangshan sequence, Beilekuduke sequence and Xikuangbei sequence formatted in extension of post-collision setting, but the Kubusunan sequence have volcanic-arc granite marking, that maybe come from magma mixing, not belongs to volcanic-arc granite.7. The granite record the process continental equilibrium adjust of“soft-collision”in Kalamaili area, so it have volcanic-arc and post-collision granite features, that take stronge evdent for rebuilding tectonic framework and recovering magma evolution , and have the implications for finding tin deposit of the Kalamaili area in East Junggar8. Basid on synthesized research, to propose the granite mixing formation mode in Kalamaili granite. Preliminary consider it is come from crust-mantle mixing, many enclaves in Huangyangshan sequence and Kubusunan sequence is the recorder of the magma mixing, host rock and enclaves have the same zircon U-Pb ages, and high positiveεNd(t), low initial 87Sr/86Sr ratios, that most powerful proof of magma mixing.

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CLC: > Astronomy,Earth Sciences > Geology > Petrology > Classification of rocks > Magmatic rocks ( igneous ) > Intrusive rocks, plutonic > Acid rock
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