论文部分内容阅读
河北武安坦岭斜长斑岩具有多斑斑状结构，基质为显微晶质结构。岩相学观察表明，斜长石斑晶有一个宽广的核部和一个宽度可变的条纹长石反应边，个别核部包含有角闪石、黑云母等矿物。基质矿物主要由蓝透闪石、条纹长石(An0Ab8.4Or91.5～An0.1Ab57.3Or42.6)、石英、钾长石(An0.3Ab5.9Or93.7～An0.3Ab4.7Or95.2)、钠长石(An0.2Ab98.3Or1.5～An0.1Ab99.2Or0.7)、磁铁矿、赤铁矿、钛铁矿、磷灰石、榍石和锆石等11种矿物组成。角闪石温压计计算结果得出，基质角闪石核部的结晶压力高于边部，核部为34.05 MPa，对应的结晶温度为660.35 ℃，结晶深度为1.29 km；边部的结晶压力为24.32 MPa，结晶温度为598.32 ℃，结晶深度为0.92 km；而斜长石斑晶中的角闪石形成时压力为159.51～178.19 MPa，温度为817.68～819.79 ℃，对应的形成深度为6.03～6.73 km。基质角闪石在Al2O3TiO2图上落在壳源区，而斑晶中的角闪石和黑云母都落在壳幔混合区。斜长石、条纹长石、磁铁矿和磷灰石的微量和稀土元素测试数据显示，其都具有相对富集LILE、亏损HFSE的特点，暗示了基质矿物的形成有流体参与。ICT三维扫描结果显示，斜长斑岩基质中的孔隙体积含量约为3.428%，铁质体积含量为4.371%，且铁氧化物和孔隙具弱连通性。通过讨论分析得出：（1）坦岭斜长斑岩中斜长石斑晶具有明显的交代结构，且晶体本身没有明显熔蚀现象，这些特征表明大量的斜长石斑晶快速上升，即“冻结岩浆房”的活化机制与流体密切相关；（2）斜长斑岩中基质矿物有十一种，且矿物类型复杂，不符合平衡系统矿物相律，应属于流体晶矿物组合；（3）坦岭斜长斑岩的基质“岩浆”可能是一种富Fe、K、P、Si、Na等元素的熔体流体流；（4）多斑斜长斑岩形成过程如下：a.深度6~7 km的深部岩浆房形成斜长石堆晶; b.富Fe、K、P、Si、Na等元素的熔体-流体流加入深部岩浆房，冻结岩浆房活化; c.由于流体超压，含大量斜长石斑晶的熔体流体在地壳浅部（0.9 km～1.2 km）呈小岩株状或岩脉状就位。多斑斜长斑岩为深部找矿提供了有力的线索。
Wu’an Tainan Ridge plagioclase porphyry has multi-speckle structure and matrix is micro-crystalline structure. Petrographic observations show that plagioclase plagioclase has a broad nucleus and a variable width of barite feldspar reaction edge, individual nuclei contain amphiboles, biotite and other minerals. The matrix minerals are mainly composed of blue tremolite, striped feldspar (An0Ab8.4Or91.5 ~ An0.1Ab57.3Or42.6), quartz, K-feldspar (An0.3Ab5.9Or93.7 ~ An0.3Ab4.7Or95.2) , Albite (An0.2Ab98.3Or1.5 ~ An0.1Ab99.2Or0.7), magnetite, hematite, ilmenite, apatite, gneiss and zircon 11 kinds of minerals. The results of amphibolite thermometer showed that the crystallization pressure of matrix hornblende was higher than that of the edge, the core was 34.05 MPa, the corresponding crystallization temperature was 660.35 ℃ and the crystallization depth was 1.29 km. The crystallization pressure of the edge And the crystallization temperature is 598.32 ℃ and the depth of crystallization is 0.92 km. While the amphiboles in plagioclase are formed at the pressure of 159.51-178.19 MPa and the temperature of 817.68-819.79 ℃, the corresponding formation depth is 6.03 ~ 6.73 km. The matrix hornblende falls on the shell source region on the Al2O3TiO2 diagram, whereas the amphiboles and biotite on the porphyrite all fall in the crust-mantle mixing zone. Trace and rare earth elements of plagioclase, stripe feldspar, magnetite and apatite show that they all have the characteristics of relatively enriched LILE and depleted HFSE, suggesting the formation of matrix minerals with fluid involvement. ICT 3D scanning results show that the pore volume of plagioclase porphyry is about 3.428%, the volume of iron is 4.371%, and the weak connectivity between iron oxide and porosimetry. Through the discussion and analysis: (1) The plagioclase phenocrysts in the Tainan plagioclase plagioclase have obvious alternation structure, and the crystal itself has no obvious corrosion phenomena. These characteristics indicate that a large number of plagioclase phenocrysts rise rapidly, that is, The activation mechanism of “frozen magma chamber” is closely related to the fluid; (2) there are eleven kinds of matrix minerals in plagioclase porphyry, and the types of minerals are complex and do not conform to the mineralogy of the balance system. ) The matrix “magma” of the Tanling plagioclase porphyry may be a melt fluid that is rich in elements such as Fe, K, P, Si and Na. (4) The formation process of the plagioclase plagioclase is as follows: a. Depth In the deep magma chamber of 6 ~ 7 km, plagioclase is formed; b. Melt-fluid flows rich in Fe, K, P, Si and Na are added to the deep magma chamber and the frozen magma chamber is activated; c. Pressure, melt fluid containing a large number of plagioclase phenocrysts in the shallow crust (0.9 km ~ 1.2 km) were small rock-like or dykes vein in place. Speckle plagioclase porphyry provides strong clues for deep prospecting.