知识与财富的链接
锡林浩特东部白音高老组火山岩主要由石泡流纹岩、珍珠岩、碎斑熔岩、流纹质熔结凝灰岩等组成。LA-MC-ICP-MS锆石U-Pb定年显示,火山岩形成于134 Ma~139 Ma之间的早白垩世。岩石地球化学研究表明:该组火山岩具有高硅、高钾、高Fe OT/Mg O比值(4.88~19.09),贫镁、钙特征,属高钾钙-碱性岩系;稀土元素表现为稀土总量较高(∑REE=82.02~436.61)、轻重稀土分馏明显(LaN/YbN=2.23~20.74)、属轻稀土富集型(LRE/HRE=2.71~11.87)、Eu负异常显著(δEu=0.06~0.42);微量元素特征表现为大离子亲石元素(LILE)Rb、Th、U、K相对较为富集,高场强元素(HFSE)Nb、Ta相对亏损,而Ba、Sr、Zr、Ti强烈亏损,与A2型花岗岩特征相似。其岩浆来源为典型的壳源岩浆系列,是陆壳岩石部分熔融的产物,形成于造山后的张性构造环境。
The volcanic rocks of Baiyingaolao Formation in the eastern Xilin Hot are composed of lithophysa rhyolite, perlite, porphyroclastic lava, and rhyolitic ignimbrite. The U-Pb ages determined by zircon by LA-ICP-MS, ranging from 134Ma to 139Ma, show that these rocks were formed in Early Cretaceous. The geochemical study suggests that they are rich in slilcon, potassium and have high FeOT/MgO (4.88～19.09) ratio, poor in magnesium, calcium and belong to the high potassium calc alkaline rock series. The samples have similar characteristics of REE patterns which are characterized by relatively high total REEcontents (∑REE=82.02～436.61),significant fractionation of LREE and HREE (LaN/YbN=2.23～20.74), attributed to the enrichment type (LR/HR=2.71～11.87) with strong negative Eu anomalies (δEu=0.06～0.42).The trace element geochemistry shows evident enrichment of LILE Rb, Th, U, and K, deficit of HFSE Nb, Ta, with strong deficit of Ba, Sr, Zr, and Ti. Theses geochemical characteristics of the volcanic rocks imply an affinity with the A2-type granite. These data indicate that the volcanic magma source was a typical crustal magme series as the product of partial melting of the continental crust which formed in an extensional tectonic environment after an orogenic event.
