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EVIDENCES 0F HUAXIONG AMALGAMATION TERRANE
- Liu Hong-ying1;2, Hu Shou-xi2, Zhou Shun-zhi2, Guo Kun-yi1, He Ju-rui1, Qie Jiang-zhong1
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1999, 5(4):
426-440.
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Huaxiong terrane at the southern margin of North China Plateform can be further subdivided into four terranes from west to east as follows: Xiaoqinling, Xiaoshan, Xiongershan and Rushan terranes, separated by NE-NNE direction faults between them. The boundary faults between these terranes a large deep faults which were developed under the deep structural settings such as crust-mantle transitional zones and were active for a 1ong time with Power and older components combined. These terranes are different in terms of stratigraphic sequences, rock assemb1ages, major elements and REE of rocks, magmatism, metallogeny and geophysics.
The basement rocks of Xiaoqinling terrane mostly consist of metasediments. Among the volcanics the intermediate-basic rocks predominate over the ultramafites. These rocks are strongly migmatized. Developed multiphase-multigenesis granites, pegmatite dikes, diabase dikes, and considerable number of gold- bearing quartz veins, rock quartz, graphite, lennilite, phosphorite, marble and skarn-type iron deposits. The metasedimentary rocks have a right slant LREE – enriched REE pattern. The elastic rocks are of higher Si and Na, and lower Ti, Fe2+, Mg, Ca and K, revealing that the crust basicity was relatively low at that time. The volcanic rocks are of higher Fe2+ and Mg, and lower Fe3+, with a gentle REE pattern and higher δEu. The corresponding rocks are similar to Condie’s TH1-type, I-type endesite and FⅡ-type dacite- rhyolite respectively. The porphyries and related molybdenum (-tungsten)deposits developed in the cover strata.
The basement of Xiaoshen terrane is thin, with few ultramafites. The metamophic grade is low. The magmatic activity is weak. Developed a few gold deposits. The metasediments and volcanics have the V-type or weak U-type REE pattern, with higher ΣREE, (La/Yb)N and sharp negative Eu-anomaly. The volcanic rocks are rich in Si, Fe3+, alkalies and Al,and
depleted in Mg, Ti, Ca and Fe2+ .The sedimentary rocks are depleted in Al, Fe2+, Mg and Ca. These factors reveal that its crust basicity was low, and its forming environment was similar in to the ancient craton. The multiphase porphyries and related molybdenum, tungsten and polymetallic deposits are found in the cover strata, mainly in Guandaokou Group.
The basement of Xiongershan terrane has a large proportion of volcanics, among which the intermediate-basic rocks and ultramafites are abundant. Developed the Yenshanian transformation type grenitoids, densely populated syntexis type small porphyry bodies and explosive breccia pipes, and related gold- molybdenum deposits. The volcanic rocks have higher Mg, ΣREE, (La／Yb)N and (Gd／Yb)N, end more distinct right-slant REE pattern. The corresponding rocks are similar to Condie’s THz-type and Ⅱ-type andesite. The clastic rocks are of lower Si and
Fe3+, and higher Al, Fe2+, Cu and Mg, indicting the 1ow degree of maturity of crust, forming environment was close to the ocean. The altered shearing zone type and quartz vein type gold deposits developed in the lower cover (Xionger Group), and the Yanshenian porphyries and related molybdenum-tungsten deposits developed in the upper cover (mainly Luanchuan Group).
The basement of Rushan terrane contains more carbonate rocks and BIF. Developed graphite, lennillte and iron mineralizations, and weak magmatism. The volcanic rocks have higher Si, Ti, Na and Fe3+, lower Mg, K. Ca, Fe2+, and relatively flat REE pattern, without Eu- anomaly. The mafic rocks are similar to Condie’s. TH1 type. The pe1iteo are of higher Mg and Ca, and lower Al and Fe2+. The large-scale and multiphase granitoids developed between XiongerGroup and KuanpinGroup in the southern part of Rushan terrane.
These separated, small scale terranes, formed by the volcano-sedimentation centers, were amalgamated together to form a combined terrane--the Huaxiong amalgamation terrane during the Zhongyue movement at 185O±150Ma.
