黑龙江省五道岭地区花岗斑岩地球化学特征及地质意义

五道岭钼矿床是伊春—延寿成矿带上最南部的矽卡岩型矿床。本次工作通过调研矿床寄主岩石边缘的花岗斑岩发现,花岗斑岩与赋矿正长花岗岩不仅形成时代一致,还存在岩石地球化学的相似性:花岗斑岩的锆石U-Pb年代学显示其形成时代为(194.1±2.0)Ma,寄主岩石正长花岗岩形成时代为(193.9±1.3)Ma;花岗斑岩为I型向A型花岗岩过渡的岩石类型,更趋近于A型花岗岩,正长花岗岩属于典型的A型花岗岩,且两者均为高Si、富K-Na、富Al的高钾钙碱性-弱碱性、准铝-过铝质的岩石,具有富集大离子亲石元素Rb、K和轻稀土元素,亏损高场强元素Nb、Ta、P、Ti等特点,两者微量和稀土元素分布趋势一致,显示它们可能是同源岩浆的产物。花岗斑岩的初始Sr比值~(87)Sr/~(86)Sr为0.723 123,结合区域地质演化特征认为,五道岭花岗质岩体可能形成于古太平洋板块俯冲挤压后期的伸展环境,矽卡岩型钼矿床的成矿作用或许与花岗斑岩的侵入密切相关,暗示区域上存在这期花岗斑岩成矿的可能性。

Geochemistry and Geological Significanceof Granite Porphyry in Wudaoling,Heilongjiang Province

Located in the southern end of Yichun-Yanshou metallogenic belt, Wudaoling molybdenum deposit is a typical skarn type deposit.Through researching on the granite porphyry on the edge of the host rocks, we found that the granite porphyry and ore-bearing syenogranite have not only the same formation age, but also the similar geochemical characteristics: the zircon U-Pb ages of the granite porphyry are 194.1±2.0 Ma, and the ore-bearing syenogranite ages are 193.9+1.3 Ma;the type of granite porphyry is transitional from I-type to A-type granites, and is more closer to A-type granites.The syenogranite typically belongs to A-type granites.Besides, both of the granites are high potassium calc-alkaline-weak-alkaline and metaluminous-peraluminous granites with enrichment in Si, K-Na and Al.The granites are enriched in LILE (Rb, K) and light rare earth elements, depleted of HFSE (Nb, Ta, P, Ti).The microelements follow the same trends as that of the rare earth elements, showing that they might be comagmatic products.The initial Sr isotope ratio 87Sr/86Sr of granite porphyry is 0.723 123.Combining with the regional geological evolution characteristics, the authors suggest that the formation of Wudaoling granitic complex was related to the extended environment after the subduction of the Ancient Pacific plate;and the mineralization of skarn type molybdenum deposit may closely relate to the granite porphyry intrusion.Regionally, it implies a mineralization possibility of the granite porphyry in this phase.