The Analysis About The Late Paleozoic Magmatic Series And Tectonic Background In Qiakuert Area

The thesis chose the magmatic belt of Qiakuert as the study area which in thenortheast margin of Junggar Basin, Xinjiang and the late Paleozoic magmatic serieswhich developed in this area as the research object. Over a large number of collectedprevious researchers’ data related geological, focused on the regional magmatic rocksand made a detailed field geological investigation. A lot of microscopic identificationof various volcanic rocks have done, and analyzed the different types of volcanic rockgeochemistry and isotope dating data within the area by systematically collected,gathered and tested. The author analyzed the genesis of various volcanic rocks on thebasis of large amounts of data, then discussed the magmatic rock series in XinjiangQiakuert area and determined the tectonic environment of Late Paleozoic.Through geochemical methods, analyzed the major elements, trace elements andrare earth elements, magmatic rocks in the study area belongs to the form from thesubduction zone to island arc environment vary from basic to acid peraluminous rockseries, the omega (Al2O3)/omega (K2O+CaO+Na2O) were greater than1, and allsamples made from ACNK-ANK diagram, you can see all of magmatic rocks in thestudy area lithology falls to the peraluminous series. Through rock chemical calculategain terman index respectively: basalt is1.98, diabase is2.46, dacite is2.25, basalticandesite is2.75, gabbro diorite is3.41, diorite is3.30, the granite is3.06, rhyolitic tuffis3.63. Reflect the two major series, namely, the former for tholeiitic series, the latterfor the calc-alkali series,another series of high potassium as potassium granite.From spider diagram of trace element and rare earth element distribution graphcan be clear that the curve is basically parallel to each has obvious homogenousdifferential evolution characteristics. Another curve to the right, according to thedistribution patterns of magmatic rocks in the study area are cognate magmaevolution.Samples of all other large ion lithophile elements (LILE), K, Ba, Srobvious enrichment, high field strength elements (HFSE), Ta, Zr, Hf, Th relativelosses, show that magmatic rocks in this area has the characteristics of fromenriched mantle.Zircon U-Pb statutory years reveals that the magmatic rocks in the study areafrom early devonian to the late devonian, the corresponding rock series are: spotseries-calcium alkali series-high potassium calc alkali series, according to northJunggar region research late silurian gram the male libraries are sedimentary whichthickness is7000m, it belongs to the trench environment, suggest that it began to divefrom this period.To late early devonian (397Ma) subduction formed tholeiitic series.In the middle devonian (392Ma) appeared calc-alkali series and in the late devonian(362.5Ma) is a high potassium calc alkali series.All of the above mentioned signsrevealed that in late Paleozoic early devonian tectonic environment as a subductionzone in Qiakuert area, middle devonian and late devonian is island arc environment.However,due to lack of isotope dating data, geotectonic environment temporarilyunable to set about the carboniferous. In addition, according to the Kekesentaointrusive granite diorite intermediated-acidic invasion time is about286.3Ma for theearly to middle Permian intrusive rocks, signed that this area entranced into thetension environment during the Permian.