CAJ | 학술논문

通过岩心观察,塔河地区海西晚期先后发育基性火山岩和中酸性火山岩两大类.两类火山岩具有不同地球化学组成:基性火山岩K_2O+Na_2O=3.490%～4.25%,K_2O/Na_2O=0.18～0.38<1,为钠质系列玄武岩,富集大离子亲石元素K、Rb、Ba、Th和高场强元素Nb、Ta、Ti、Zr、P,δ Eu≈1,无明显亏损;中酸性火山岩表现为高场强元素Nb、Ta、Sr、P、Ti亏损,大离子亲石元素K、R.b、Ba、Th较为富集,稀土元素δ Eu=0.43～0.66<1, 铕具明显负异常特征,K_2O+Na_2O=6.86%～8.82%,K_2O/Na_2O=1.25～1.59>1,为钾玄或高钾钙碱性系列英安岩.强不相容元素Th/Ta、Nb/U比值说明,玄武岩与英安岩成因没有明显亲缘性,玄武岩来源于地幔,英安岩来源于地壳.结合邻区火成岩对比分析,塔河地区发育的玄武岩、英安岩分别与塔中地区玄武岩和南天山分区花岗岩具有相同的地球化学特征,构造判别图解表明,玄武岩形成于板内主裂陷期,英安岩、花岗岩形成于板块边缘岛弧构造环境,作为特殊古构造位置,塔河地区先后发育的玄武岩、英安岩为板内主裂陷盆地边缘和弧火山边缘相互耦合的产物.
통과암심관찰,탑하지구해서만기선후발육기성화산암화중산성화산암량대류.량류화산암구유불동지구화학조성:기성화산암K_2O+Na_2O=3.490%～4.25%,K_2O/Na_2O=0.18～0.38<1,위납질계렬현무암,부집대리자친석원소K、Rb、Ba、Th화고장강원소Nb、Ta、Ti、Zr、P,δ Eu≈1,무명현우손;중산성화산암표현위고장강원소Nb、Ta、Sr、P、Ti우손,대리자친석원소K、R.b、Ba、Th교위부집,희토원소δ Eu=0.43～0.66<1, 유구명현부이상특정,K_2O+Na_2O=6.86%～8.82%,K_2O/Na_2O=1.25～1.59>1,위갑현혹고갑개감성계렬영안암.강불상용원소Th/Ta、Nb/U비치설명,현무암여영안암성인몰유명현친연성,현무암래원우지만,영안암래원우지각.결합린구화성암대비분석,탑하지구발육적현무암、영안암분별여탑중지구현무암화남천산분구화강암구유상동적지구화학특정,구조판별도해표명,현무암형성우판내주렬함기,영안암、화강암형성우판괴변연도호구조배경,작위특수고구조위치,탑하지구선후발육적현무암、영안암위판내주렬함분지변연화호화산변연상호우합적산물.
Core observation shows that mafic volcanic and intermediate-acidic volcanic rocks were developed successively in Tahe area in Late Hercynian. These two types of volcanic rocks have different geochemical compositions. In mafic volcanic rock, K_2O+Na_2O=3.49%～4.25%,K_2O/Na_2O=0.18～0.38<1, large-ion lithophile elements (LILE) K, Rb, Ba, Th and high-field strength elements (HFSE) Nb, Ta, Ti, Zr, P are high, and δEu ≈ 1, with no significant anomaly, suggesting that this type of volcanic rock belongs to the sodic series basalt As for intermediate-acidic volcanic rock, K_2O+Na_2O= 6.86%～8.82%,K_2O/Na_2O=1.25～1.59>l, HFSE Nb, Ta, Sr, P, Ti are poor, LILE K, Rb, Ba, Th are high, and δ Eu=0.43～0.66<l, with negative anomaly, implying that this kind of volcanic rock is potash basaltic or high potassium-calcium alkaline -dacite. The HFSE ratios Th/Ta and Nb/U imply that basalt and dacite don't have obvious affinity, the basalt originated from the mantle, whereas the dacite originated from the crust A comparison with the igneous rocks of adjacent areas shows that the basalt and dacite are similar respectively to the basalt in Tazhong and the granite in South Tianshan in geochemical characteristics. An analysis of tectonic sub -diagram reveals that the basalt was formed in the intraplate rift, whereas the dacite and granite were formed on the edge of the island arc plate tectonic setting. As a special paleo-tectonic location, Tahe area has well-developed basalt and dacite, which are the coupling results of the intraplate main rift basin and the volcanic-arc edge.