CAJ | 학술논문

大兴安岭北部奇乾一带的新元古界佳疙瘩组上部由灰黑色致密枕状玄武岩、含气孔-杏仁状构造的枕状玄武岩夹灰黑色粉砂质板岩、绿泥片岩和灰色薄层大理岩化灰岩组成。枕状玄武岩由斜长石、辉石、绿泥石等组成。地球化学特征表明，岩石为富钠碱性玄武岩，稀土元素总量较高∑REE为107.71×10-6~127×10-6，轻稀土富集LREE/HREE为5.15~5.56，(La/Yb)N为4.44~5.18，δ Eu=0.86~1.08，稀土元素配分曲线为右倾型。微量元素与MORB相比，富集Ti，Sr、K、Rb、Ba等不相容元素，Y、Yb含量略低于MORB，Y、Yb相对亏损。构造环境判别显示该枕状熔岩形成于大洋板内洋岛环境，佳疙瘩组洋岛玄武岩的发现标志着此时已经有成熟的大洋壳形成；综合玄武岩的地质地球化学特征，认为其源区来自软流圈地幔或与地幔柱组分有关。
대흥안령북부기건일대적신원고계가흘탑조상부유회흑색치밀침상현무암、함기공-행인상구조적침상현무암협회흑색분사질판암、록니편암화회색박층대리암화회암조성。침상현무암유사장석、휘석、록니석등조성。지구화학특정표명，암석위부납감성현무암，희토원소총량교고∑REE위107.71×10-6~127×10-6，경희토부집LREE/HREE위5.15~5.56，(La/Yb)N위4.44~5.18，δ Eu=0.86~1.08，희토원소배분곡선위우경형。미량원소여MORB상비，부집Ti，Sr、K、Rb、Ba등불상용원소，Y、Yb함량략저우MORB，Y、Yb상대우손。구조배경판별현시해침상용암형성우대양판내양도배경，가흘탑조양도현무암적발현표지착차시이경유성숙적대양각형성；종합현무암적지질지구화학특정，인위기원구래자연류권지만혹여지만주조분유관。
Lying in the Ergun massif, the Jiageda Formation is a part of the Xing’an orogenic belt. It is composed of pillow lava, schist, mica-schist, marble, marbleized limestone and meta-basalt rocks. The meta-basalt rocks with pillow structure in the Jiageda Formation are Na-rich Na alkaline basalts, with high content of TiO2, P2O5 and Na2O;the rare-earth elements are characterized by right-oblique strong LREE-enrichment patterns and high∑REE values of 107.71 × 10-6~127 × 10-6;the rocks are enriched in such HFSH as Nb, Ta, Zr, Hf as well as such LILE as Rb, Sr, Ba and LREE, with LREE/HREE ratios being 5.15-5.56, (La/Yb)N being 4.44-5.18, andδ Eu being 0.86~1.08. <br> The trace element patterns are of the upward-bulging K-Ti enrichment type, and their multi-component plots fall within the fields of oceanic island basalts and alkali basalts. These basalts are characterized by the tectonic setting of the oceanic intraplate alkaline basalts. The geochemical characteristics indicate that the meta-basalt rocks belong to the OIB. The discovery of the OIB shows that there once existed well-developed Palaeo-oceanic crust. Judging from the geological and geochemical features of the meta-basalt rocks in the area,the authors conclude that they were derived from the asthenosphere mantle or mantle plume.