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The Petrological Characteristics Of Mesozoic Volcanic Rocks In Sonidzuoqi, Inner Mongolia

Posted on:2016-01-24Degree:MasterType:Thesis
Country:ChinaCandidate:X ZhangFull Text:PDF
GTID:2180330479950020Subject:Mineralogy, petrology, ore deposits
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This paper based on "Inner Mongolia 1:50000 Zhunheremuyin Sumu six pieces of regional geological survey" project, carry out research on Mesozoic volcanic rocks of Sonidzuoqi Area Inner Mongolia. The tectonic location of the study area in the southeast of Siberian Plate continental margin,the belt of Proliferation in Late Paleozoic and it is located in the northwestern of Erlianhot-Hegenshan fault zone. It belonged to the paleo Asian tectonic domain of the orogenic belt when in Paleozoic. while in Mesozoic, it belonged to West Pacific tectonic domain. Study division of tectonic units belongs to the northern orogenic belt of Xingmeng orogenic belt in the northweatern border region of Inner Mongolia.In the area, Magmatic activities often occurs. The volcanic eruptions and the activities of Magmatic intrusion occus severely in Late Paleozoic and Mesozoic.Mesozoic volcanic rocks only occur in the 1:50000 Zhunheremuyin Sumu piece of regional geological survey and it is distributed in belt. In the northeast corner of this piece and neighboring piece, mesozoic volcanic rocks are unconformity with alkali feldspar granite.The Baiyingaolao volcanic rocks are unconformity with damoguaihe volcanic rocks of the Cretaceous in Hong Ge Er is located in NNE fault zone. The volcanic rocks grow almost upright cleavage and fold structure. This volcanic rocks including Rhyolite, Tuff,Ignimbrite, Dacite and thin layer Obsidian. At the southern and the northern of Baiyingaolao volcanic rocks,it is invaded by Biotite-adamellite of Carboniferous.In this paper,the zircon particles from mesozoic volcanic rocks are seldom,which are used to measuring age by LA-ICA-MS and they are Inherited zircon.The age result of Inherited zircon indicates the formation age of alkali feldspar granite in Carboniferous.It discovery their have the same geochemistry characteristics and the same magma characteristic by comparing with Baoyingaolao volcanic rocks in the adjacent area.So,I think they are same period volcanic rocks.According to the two LA-ICP-MS zircon U-Pb dating weighted average age were 135.1 ± 5.6Ma and135.2 ± 3.8 Ma of the Baiyingaolao volcanic rocks in Zhunheremuyin Sumu,so we can reference these rocks in this paper are formed in early Cretaceous.In the 1:50000 Zhunheremuyin Sumu six pieces of regional geological survey report,the former named the volcanic rocks in this paper second segment of Baoligaomiao volcanic rocks but in this paper we named it Baiyingaolao volcanic rocks again.Geochemical data of Mesozoic volcanic rocks in Sunitezuoqi show the content of Si O2 of volcano rock changes between 69.52wt%-71.44wt%,these volcanic rocks are rich in potassium and aluminum(the content of K2O= 3.92wt%-4.72wt% and Al2O3=14.17wt%-14.7wt%). the content of(Na2O+K2O) volcano rock changes between7.6wt%-8.78wt%, and that the Litman index δ is 2.15-2.71, belonging to the calcalkaline series, ratio range between 0.99-1.10 A/CNK, A/NK 1.25-1.39, belonging to the metaluminous to weakly peraluminous rocks. REE diagram shows that the volcano rock LREE enrichment, HREE loss, ratio range between 23.31-39.98(La/Yb)N indicates the volcano rocks have a strong fractionation between LREE and HREE. It shows that the magma of the volcano rocks comes from the thickened lithosphere in the post-orogenic tectonic setting. The trace element spider diagrams show that the volcano rocks are enriched in enrichment of Rb, Ba,Th and other large ion lithophile elements( LILE) and loss of Nb、Ta、Ti.In addition,Sr and P shows negative anomaly and this result by evoluting of magma,so the magma of the volcano rock in this paper is from magmatic evolution of the thickened lithosphere in the post-orogenic tectonic setting and the volcano rock is formed by the southward subduction of Mongolia-Okhotsk oceanic plate.
Keywords/Search Tags:Sonid Zuoqi, Mesozoic volcanic rocks, Mongolia-Okhotsk oceanic, Lithospheric mantle
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