基性岩侵入对页岩矿物学特征的影响:以松辽盆地嫩江组为例

已有研究表明岩浆侵入对页岩矿物学特征产生影响，然而对其影响范围及程度缺少精细解剖，制约了岩浆活动对页岩矿物学特征影响机理的准确认识.以松辽盆地南部与辉绿岩接触的嫩江组页岩为对象，利用岩心观察、XRD、偏光显微镜及扫描电镜等手段，将接触带页岩距辉绿岩由远及近划分为5个带:（1）灰色页岩带，厚19 m，（2）深灰色页岩带，厚11 m，（3）灰黑色页岩带，厚12.9 m，（4）青灰色页岩带，厚1.5 m，（5）灰白色页岩带，厚2.2 m.石英含量增多，平均含量分别为27.0%、33.6%、51.7%、56.7%和52.7%，由陆源碎屑石英过渡为高温自生石英（微晶自形石英及微晶球状石英），重结晶现象加剧；长石含量增多，平均含量分别为8.8%、12.0%、14.0%、15.1%和18.2%，由他形过渡为半自形-自形，重结晶现象加剧；碳酸盐矿物含量先减少后增多，平均含量分别为9.0%、10.0%、7.5%、4.5%和6.0%，菱铁矿及方解石由自形过渡为胶状及脉状；黄铁矿含量逐渐减少，平均含量分别为5.4%、3.5%、1.0%、0%和0%，由草莓状及自形过渡为他形粒状；粘土矿物含量逐渐减少，平均含量分别为46.0%、36.5%、22.5%、20.1%和19.0%，由片状蒙脱石过渡为絮状伊利石.结果表明，基性岩侵入页岩不仅加速了页岩成岩演化进程，而且使页岩脆性矿物增加、塑性矿物减少，可提高页岩储层的脆性及可压性，减弱了页岩气的赋存能力. 

Effects of Basic Intrusions on Shale Mineralogy:A Case Study from Nenjiang Formation in Songliao Basin

Existing studies have shown that magmatic intrusion has effects on shale mineralogical characteristics, but the lack of a detailed anatomy of its scope and extent has restricted the accurate understanding of the influence mechanism of magmatic activities on shale mineralogical characteristics.Based on contact with diabase in southern Songliao basin shale as an object of the Nenjiang Formation, by means of core observation, XRD, polarizing microscope, and scanning electron microscopy, the contact zone shale is divided from the diabase intrusion from far and near into five zones: gray shale zone, 19 m thick; dark gray shale zone, thick 11 m; gray-black shale zone, 12.9 m thick; blue-gray shale zone, 1.5 m thick; gray-white shale zone, 2.2 m thick. Quartz content increases, with average contents of 27.0%, 33.6%, 51.7%, 56.7%, and 52.7%, respectively. The transition from terrestrial clastic quartz to high-temperature in-situ quartz (microcrystalline self-shaped quartz and microcrystalline spherical quartz), the recrystallization phenomenon intensified. The content of feldspar increases, with average contents of 8.8%, 12.0%, 14.0%, 15.1%, and 18.2%, respectively, which changes from semi-morphic to semi-self-shaped, and the recrystallization phenomenon intensified. The content of carbonate minerals decreases first and then increased, with the average contents of 9.0%, 10.0%, 7.5%, 4.5%, and 6.0%, respectively. The shape of siderite and calcite changes from self-shaped to colloidal and veined. The pyrite content gradually decreases, with average contents of 5.4%, 3.5%, 1.0%, 0%, and 0%, respectively, and transformed from strawberry-like and self-shaped to other-shaped granular. The clay mineral content gradually decreases, with average contents of 46.0%, 36.5%, 22.5%, 20.1%, and 19.0%, respectively, transformed from platy montmorillonite to floc illite.The results show that the intrusion of basic rock into shale not only accelerates the diagenetic evolution of shale, but also increases the brittle minerals and decreases the plastic minerals, which can improve the brittleness and compressibility of shale reservoirs but weaken the ability of shale gas to exist.