西北地质
西北地質
서북지질
Northwestern Geology
2015年
4期
37-49
,共13页
祖尔肯乌拉山%中新世%查保马组%火山岩%锆石 U-Pb 测年
祖爾肯烏拉山%中新世%查保馬組%火山巖%鋯石 U-Pb 測年
조이긍오랍산%중신세%사보마조%화산암%고석 U-Pb 측년
Mt. Jurhen Ul%Miocene%Chabaoma Formation%volcanic rocks%zircon U-Pb dating
祖尔肯乌拉山地区查保马组陆相火山岩岩石类型主要为粗安岩和安山岩,属新近纪中新世。地球化学特征显示：主量元素 SiO2含量为42.45%~62.60%,绝大部分为58.08%~62.60%,相对富集 FeO、MgO、K2 O、TiO2、P2 O5,属幔源岩浆岩系列。里特曼指数σ=2.87~3.41,平均3.19,属于钙碱性岩系。火山岩的全碱(Na2 O + K2 O)含量高,且 Na2 O –2< K2 O, K2 O/Na2 O=1.12~1.43,属钾玄岩系；微量元素强不相容元素 Rb、Ba、Th、U、K 呈强富集,弱不相容元素 Ta、Nb、La、Ce、P、Zr、Hf、Sm 弱富集,过度元素 Ti、Y、Yb 弱亏损,相容元素 Lu 强亏损。富集强不相容元素,指示火山岩源区为富集地幔(EMⅡ)；稀土元素为右倾型,轻重稀土分馏显著,具有弱的负 Eu 异常特征,显示岩浆在上涌过程中有地壳的物质混入,发生同化混染作用。构造环境分析为板内。根据 ICP-MS 锆石 U-Pb 法测得火山岩锆石结晶年龄为(20±1)Ma,属新近纪中新世。
祖爾肯烏拉山地區查保馬組陸相火山巖巖石類型主要為粗安巖和安山巖,屬新近紀中新世。地毬化學特徵顯示：主量元素 SiO2含量為42.45%~62.60%,絕大部分為58.08%~62.60%,相對富集 FeO、MgO、K2 O、TiO2、P2 O5,屬幔源巖漿巖繫列。裏特曼指數σ=2.87~3.41,平均3.19,屬于鈣堿性巖繫。火山巖的全堿(Na2 O + K2 O)含量高,且 Na2 O –2< K2 O, K2 O/Na2 O=1.12~1.43,屬鉀玄巖繫；微量元素彊不相容元素 Rb、Ba、Th、U、K 呈彊富集,弱不相容元素 Ta、Nb、La、Ce、P、Zr、Hf、Sm 弱富集,過度元素 Ti、Y、Yb 弱虧損,相容元素 Lu 彊虧損。富集彊不相容元素,指示火山巖源區為富集地幔(EMⅡ)；稀土元素為右傾型,輕重稀土分餾顯著,具有弱的負 Eu 異常特徵,顯示巖漿在上湧過程中有地殼的物質混入,髮生同化混染作用。構造環境分析為闆內。根據 ICP-MS 鋯石 U-Pb 法測得火山巖鋯石結晶年齡為(20±1)Ma,屬新近紀中新世。
조이긍오랍산지구사보마조륙상화산암암석류형주요위조안암화안산암,속신근기중신세。지구화학특정현시：주량원소 SiO2함량위42.45%~62.60%,절대부분위58.08%~62.60%,상대부집 FeO、MgO、K2 O、TiO2、P2 O5,속만원암장암계렬。리특만지수σ=2.87~3.41,평균3.19,속우개감성암계。화산암적전감(Na2 O + K2 O)함량고,차 Na2 O –2< K2 O, K2 O/Na2 O=1.12~1.43,속갑현암계；미량원소강불상용원소 Rb、Ba、Th、U、K 정강부집,약불상용원소 Ta、Nb、La、Ce、P、Zr、Hf、Sm 약부집,과도원소 Ti、Y、Yb 약우손,상용원소 Lu 강우손。부집강불상용원소,지시화산암원구위부집지만(EMⅡ)；희토원소위우경형,경중희토분류현저,구유약적부 Eu 이상특정,현시암장재상용과정중유지각적물질혼입,발생동화혼염작용。구조배경분석위판내。근거 ICP-MS 고석 U-Pb 법측득화산암고석결정년령위(20±1)Ma,속신근기중신세。
In the Chabaoma Formation of Mt. Jurhen Ul area,the main rock types of continental volcanic rockare latite and andesite,which were formed in Neogene-Miocene epoch. The geo-chemical characteristics indicate that the contents of SiO2 (main element)range from 42.45% to 62.60%,and most of them are 58.08%-62.60%,which is relatively higher than the ones of FeO,MgO,K2 O,TiO2 and P2 O5 ,suggesting these rocks belong to the ones of mantle-derived magmatic rock series. The values of σ(Litman index)are 2.87-3.41,with an average of 3.1 9, showing these rocks have the characteristics of calc-alkaline rock series. The total alkali (Na2 O+K2 O)contents of these volcanic rocks are high,the contents of Na2 O-2 are less than the ones of K2 O,and the ratios of K2 O/Na2 O are 1.12-1.43,suggesting theses rocks belong to shoshonite-series.For the trace elements,the strong incompatible elements (such as Rb,Ba,Th,U and K) showstrong enrichment,but the weakly incompatible elements (Ta,Nb,La,Ce,P,Zr,Hf and Sm)show weak enrichment,while the transition elements (Ti,Y and Yb)are weakly less,and the compatible element (Lu)is strong loss.The strong enrichment of incompatible elements re-veal that these volcanic rocks were soured from the enriched mantle (EM II). The distribution model of REE is right abligue in the orientation,with significant REE fractionation and weak negative Eu anomalies,suggesting that the crustal material had mixed into the magma during the upwelling process,which lead to the occurring of assimilation and hybridization. The analysis show that,these rocks formed in an intraplate setting. The ICP-MS zircon U-Pb dating reveals that the crystallization ages of these volcanic rocks are 20±1Ma,belonging to the Miocene Epoch of Neogene Period.
