發(fā)布時間：2018-07-29 12:57

【摘要】：攀枝花式鐵礦賦存巖體頂部普遍發(fā)育有富角閃石細脈。本文報道了白馬鐵礦青杠坪剖面頂部細粒橄欖輝長巖中富角閃石細脈、蝕變帶和寄主巖中代表性斜長石、磁鐵礦、鈦鐵礦、角閃石、黑云母和磷灰石等礦物的電子探針分析。巖相學(xué)觀察表明,細脈中礦物主要為大顆粒角閃石,其間充填鈦鐵礦、斜長石、方解石;蝕變帶中礦物為角閃石、輝石、斜長石、黑云母、磁鐵礦及鈦鐵礦,礦物普遍發(fā)生蝕變(如黑云母綠泥石化),斜長石邊部也發(fā)生溶蝕;靠近蝕變帶的寄主巖中礦物主要為斜長石、單斜輝石(二者含量相近),另含少量角閃石、黑云母、磁鐵礦和鈦鐵礦,在鈦鐵氧化物周圍還有黃鐵礦、黃銅礦和磷灰石,礦物也發(fā)生了輕微的蝕變;而遠離細脈的新鮮寄主巖中礦物主要為新鮮的斜長石、單斜輝石(二者含量相近),少量橄欖石、角閃石、黑云母、磁鐵礦及鈦鐵礦。電子探針數(shù)據(jù)表明,寄主巖中的斜長石An比細脈及蝕變帶中的斜長石An要高。新鮮寄主巖中的斜長石主要為拉長石,蝕變帶中的斜長石主要為中長石,而細脈中出現(xiàn)了鈉長石。運用角閃石全鋁壓力計對富角閃石細脈中的角閃石顆粒進行了壓力和深度的計算,從中心到邊部所估算的壓力表現(xiàn)出先增大后減小的趨勢:69MPa→121MPa→167MPa→128MPa;運用磁鐵礦-鈦鐵礦共生的溫度計和氧逸度計,計算了寄主巖中磁鐵礦和鈦鐵礦平衡時的溫度和氧逸度,結(jié)果表明,磁鐵礦和鈦鐵礦平衡的溫度較低為546~574℃,氧逸度(logfO2)為-20.41~-23.83。另外,根據(jù)黑云母的Ti-Mg/(Mg+Fe)溫度估算圖解,靠近蝕變帶寄主巖中黑云母的結(jié)晶溫度為700~720℃。通過討論分析得出結(jié)論:(1)青杠坪鎂鐵質(zhì)侵入體侵位后頂部及周圍先固結(jié)形成頂部細粒橄欖輝長巖帶,對底部的含礦流體成礦起到屏蔽層的作用。(2)細脈和蝕變帶中斜長石更富Na;由角閃石核部電子探針數(shù)據(jù)計算出的侵位深度為巖石的真實侵位深度,而由邊部電子探針數(shù)據(jù)計算的深度為流體高壓導(dǎo)致的"假"侵位深度;從富角閃石細脈到蝕變帶再到寄主巖,礦物的結(jié)晶溫度逐漸降低,對應(yīng)流體高溫到低溫的擴散特點。(3)這種富角閃石細脈可以作為深部礦床的淺部標(biāo)志,對深部礦床的勘察找靶提供了一種方法。
[Abstract]:Hornblende veins are commonly developed at the top of Panzhihua iron ore deposit. In this paper, the electron probe analysis of typical plagioclase, magnetite, ilmenite, hornblende, biotite and apatite minerals in amphibole veins, altered zones and host rocks at the top of Qingzangping section of Baima Iron Mine is reported. The petrographic observations show that the minerals in the vein are mainly large grained hornblende, filled with ilmenite, plagioclase and calcite, and the minerals in the altered zone are hornblende, pyroxene, plagioclase, biotite, magnetite and ilmenite. Alteration of minerals (such as biotite greenstone) and dissolution of plagioclase edge are common, and the host rocks near the altered zone are mainly plagioclase, clinopyroxene (similar in both contents), and a small amount of hornblende and biotite, Magnetite and ilmenite, as well as pyrite, chalcopyrite and apatite around the titanium-iron oxides, have also undergone slight alteration, while the minerals in the fresh host rocks far from the veins are mainly fresh plagioclase. Clinopyroxene (similar in content), a small amount of olivine, hornblende, biotite, magnetite and ilmenite. The electron probe data show that the n of plagioclase in host rock is higher than that in vein and alteration zone. The plagioclase in the fresh host rock is mainly elongated, the plagioclase in the alteration zone is mainly meso-feldspar, and albite appears in the vein. The pressure and depth of hornblende particles in the rich amphibole veins were calculated by using the amphibole all-aluminum pressure gauge. The estimated pressure from the center to the edge shows a trend of first increasing and then decreasing. The temperature and oxygen fugacity of magnetite and ilmenite equilibrium in host rock are calculated by using the thermometer and oxygen fugacity of magnetite and ilmenite symbiosis, using the temperature and oxygen fugacity of magnetite and ilmenite in the host rock. The results show that the equilibrium temperature of magnetite and ilmenite is lower than that of ilmenite, and the oxygen fugacity (logfO2) is -20.41 ~ 23.83 鈩，

本文編號：2152743