TY - JOUR
T1 - Occurrence of an Alaskan-type complex in the Middle Tianshan Massif, Central Asian Orogenic Belt
T2 - Inferences from petrological and mineralogical studies
AU - Su, Ben Xun
AU - Qin, Ke Zhang
AU - Sakyi, Patrick Asamoah
AU - Malaviarachchi, Sanjeewa P.K.
AU - Liu, Ping Ping
AU - Tang, Dong Mei
AU - Xiao, Qing Hua
AU - Sun, He
AU - Ma, Yu Guang
AU - Mao, Qian
PY - 2012/2/1
Y1 - 2012/2/1
N2 - The Xiadong mafic-ultramafic complex lies in the central part of the Middle Tianshan Massif (MTM), along the southern margin of the Central Asian Orogenic Belt (CAOB). This complex is composed of dunite, hornblende (Hbl) clinopyroxenite, hornblendite, and Hbl gabbro. These rocks are characterized by adcumulated textures and variable alteration. Orthopyroxene is an extremely rare mineral in all rock units and plagioclase is absent in dunite and Hbl clinopyroxenite. Hbl, Fe-chromite, and Cr-magnetite are common phases. Olivines have forsterite (Fo) contents ranging from 92.3 to 96.6. Clinopyroxenes are Ca-rich, Ti-poor diopsides, and mostly altered to tremolites or actinolites. Chromites display low TiO 2 and Al 2O 3 contents and high Cr# and Fe 2+/(Fe 2++Mg) values. Primary and secondary Hbls show wide compositional variations. These petrological and mineralogical features as well as mineral chemistry are comparable to typical Alaskan-type complexes worldwide, which are widely considered to have formed above subduction zones. The chemistry of clinopyroxene and chromite supports an arc plate-tectonic origin for the Xiadong complex. Its confirmation as an Alaskan-type complex implies that the MTM, with Precambrian basement, was probably a continental arc during oceanic plate underflow and further supports the hypothesis of southward subduction of the Palaeozoic Junggar Ocean.
AB - The Xiadong mafic-ultramafic complex lies in the central part of the Middle Tianshan Massif (MTM), along the southern margin of the Central Asian Orogenic Belt (CAOB). This complex is composed of dunite, hornblende (Hbl) clinopyroxenite, hornblendite, and Hbl gabbro. These rocks are characterized by adcumulated textures and variable alteration. Orthopyroxene is an extremely rare mineral in all rock units and plagioclase is absent in dunite and Hbl clinopyroxenite. Hbl, Fe-chromite, and Cr-magnetite are common phases. Olivines have forsterite (Fo) contents ranging from 92.3 to 96.6. Clinopyroxenes are Ca-rich, Ti-poor diopsides, and mostly altered to tremolites or actinolites. Chromites display low TiO 2 and Al 2O 3 contents and high Cr# and Fe 2+/(Fe 2++Mg) values. Primary and secondary Hbls show wide compositional variations. These petrological and mineralogical features as well as mineral chemistry are comparable to typical Alaskan-type complexes worldwide, which are widely considered to have formed above subduction zones. The chemistry of clinopyroxene and chromite supports an arc plate-tectonic origin for the Xiadong complex. Its confirmation as an Alaskan-type complex implies that the MTM, with Precambrian basement, was probably a continental arc during oceanic plate underflow and further supports the hypothesis of southward subduction of the Palaeozoic Junggar Ocean.
KW - Alaskan-type mafic-ultramafic complex
KW - Central Asian Orogenic Belt
KW - Middle Tianshan Massif
KW - continental arc
KW - mafic-ultramafic complex
UR - http://www.scopus.com/inward/record.url?scp=84863115441&partnerID=8YFLogxK
U2 - 10.1080/00206814.2010.543009
DO - 10.1080/00206814.2010.543009
M3 - Review article
SN - 0020-6814
VL - 54
SP - 249
EP - 269
JO - International Geology Review
JF - International Geology Review
IS - 3
ER -