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宾夕法尼亚州西南费耶特县浅成相金伯利岩中有两种化学特征明显不同的巨晶和包体:富铬类型的和贫铬类型的。富铬类型由橄榄石(Fo=90-93)、石榴子石(1.64—6.14％的Cr_2O_3)、透辉石(1.89—2.34％的Cr_2O_3)、铬尖晶石和不混溶的硫化物熔体组成。它们的mg变化范围小,其主要元素的组成与受过剪切的石榴子石二辉橄榄岩的相似。次要元素的变化与48—39千巴压力范围内、温度区1310°—1055℃的晶体分离作用一致。贫铬类型演化程度更高。它们由橄榄石(Fo=81-85)、石榴子石(<0.1％Cr_2O_3)、镁钛铁矿(16—37mol％。MgTiO_3;0.05—2.05％Cr_2O_3)和透辉石(<0.1％Cr_2O_3)组成,代表了低速带内贫铬熔浆分离程度较高的阶段。这两种类型的巨晶和包体与它们的寄主熔浆混合,使两种橄榄石表现出了Fo=88-89的反应边和钛铁矿巨晶中的反环带(34—51mol％的MgTiO_3;1.4—3.6％Cr_2O_3)。贫铬类型者是从岩浆房里的熔体中结晶出来的。这些熔体是在低速带从上升的底辟体内分疑的。这些熔体内的结晶分异作用导致了矿物成分的演化和钛铁矿的晶出。而富铬类型代表在上升的底辟体中的熔体内,晶体和不混溶硫化物熔体的分离产物;在这种熔体中,熔体/晶体的比值是低的,熔体中主要元素的成分被周围的地幔成分(未亏损的石榴子石二辉橄榄岩)所缓冲。含有熔体的底辟体上升,破坏了演化程度较高的、贫铬的、包含巨晶的晶体糊状物,导致寄主熔体混合。逆反应和同源捕虏晶在混染岩浆内的结晶,形成了所观察到的环带类型。
There are two distinctly different megacrysts and inclusions in the epithermal kimberlite in the Fayette County, southwestern Pennsylvania: chromium-rich and chromium-poor. The chromium-rich type is composed of olivine (Fo = 90-93), garnet (1.64-6.14% Cr 2 O 3), diopside (1.89-2.34% Cr 2 O 3), chrome spinel and immiscible sulfide melt composition. They have a small range of mg variation and their major elements are similar in composition to the sheared garnet lherzolites. The variation of the secondary elements is consistent with the crystal separation in the pressure range of 48-39 kPa and temperature in the range of 1310 ° -1055 ° C. Chromium-depleting types evolve more. They are composed of olivine (Fo = 81-85), garnet (<0.1% Cr 2 O 3), ilmenite (16-37 mol% MgTiO 3; 0.05-2.05% Cr 2 O 3) and diopside (<0.1% Cr 2 O 3) Composition, represents the low-speed strip of molten chromium separation stage of a higher degree. Both types of macroscopies and inclusions are mixed with their host melt to render both olivines reaction edges of Fo = 88-89 and anti-cyclones in the ilmenite megacrysts (34-51 mol% Of MgTiO_3; 1.4-3.6% Cr_2O_3). Chromium-poor types crystallize out of the melt in the magma chamber. These melts are suspicious at low speeds from elevated diaphragms. Crystallization within these melts causes the evolution of mineral composition and ilmenite crystallinity. Whereas the chromium rich type represents the product of the separation of the crystalline and immiscible sulfide melts in the ascending tundra; in this melt, the melt / crystallite ratio is low, and in the melt The major elemental components are buffered by the surrounding mantle component (unrecovered garnet lherzolite). The rise of the diaspore containing the melt disrupts the more evolved, chrome-depleted, macroscopically crystalline paste that causes the host melt to mix. The reverse reaction and homoclinic crystals crystallize within the contaminated magma, forming the observed type of annulus.