Biotite‐rich selvedges developed between mafic schollen and semipelitic diatexite in migmatites at Lac Kenogami in the Grenville Province of Quebec. Mineral equilibria modelling indicates that partial melting occurred in the mid‐crust (4.8–5.8 kbar) in the range 820–850°C. The field relations, petrography, mineral chemistry and whole‐rock composition of selvedges along with their adjacent mafic schollen and host migmatites are documented for the first time. The selvedges measured in the field are relatively uniform in width (~1 cm wide) irrespective of the shape or size of their mafic scholle. In thin section, the petrographic boundary between mafic scholle and selvedge is defined by the appearance of biotite and the boundary between selvedge and diatexite by the change in microstructure for biotite, garnet, plagioclase and quartz. Three subtypes of selvedges are identified according to mineral assemblage and microstructure. Subtype I have orthopyroxene but of different microstructure and Mg# to orthopyroxene in the mafic scholle; subtype II contain garnet with many mineral inclusions, especially of ilmenite, in contrast to garnet in the diatexite host which has few inclusions; subtype III lack orthopyroxene or garnet, but has abundant apatite. Profiles showing the change in plagioclase composition from the mafic schollen across the selvedge and into the diatexite show that each subtype of selvedge has a characteristic pattern. Four types of biotite are identified in the selvedges and host diatexite based on their microstructural characteristics. (a) Residual biotite forms small rounded red‐brown grains, mostly as inclusions in peritectic cordierite and garnet in diatexite; (b) selvedge biotite forms tabular subhedral grains with high respect ratio; (c) diatexite biotite forms tabular subhedral grains common in the matrix of the diatexite; and (d) retrograde biotite that partially replaces peritectic cordierite and garnet in the diatexite. The four groups of biotite are also discriminated by their major element (EMPA) and trace elements (LA‐Q‐ICP‐MS) compositions. Residual biotite is high in TiO2 and low in Sc and S, whereas retrograde biotite has high Al2O3, but low Sc and Cr. Selvedge and diatexite biotite are generally very similar, but selvedge biotite has higher Sc and S contents. Whole‐rock compositional profiles across the selvedges constructed from micro‐XRF and LA‐Q‐ICP‐MS analyses show: (a) Al2O3, FeO, MgO and CaO all decrease from mafic scholle across the selvedge and into the diatexite; (b) Na2O is lowest in the mafic scholle, rises through the selvedge and reaches its maximum about 20–30 mm into the diatexite host; (c) K2O is lowest in the mafic scholle and reaches its highest value in the first half of the selvedge, then declines before reaching a higher, but intermediate value, about 20 mm into the diatexite. Of the trace elements, Cs and Rb show distributions very similar to K2O.

中文翻译：

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半泥质杂岩混合岩中镁铁质schollen周围富含黑云母的反应边缘的显微结构和成分变化

在魁北克格伦维尔省 Lac Kenogami 的混合岩中，在镁铁质 schollen 和半泥质混岩之间形成了富含黑云母的织边。矿物平衡模型表明，部分熔化发生在 820-850°C 范围内的地壳中部 (4.8-5.8 kbar)。首次记录了边沿及其相邻的镁铁质岩浆和主混合岩的场关系、岩石学、矿物化学和全岩组成。在现场测量的布边在宽度上相对均匀（约 1 厘米宽），而与它们的镁铁质梭叶的形状或大小无关。在薄片中，镁铁质斜长石和织边之间的岩相边界由黑云母的出现来定义，织边和硅通岩之间的边界由黑云母、石榴石、斜长石和石英的微观结构变化来定义。根据矿物组合和微观结构确定了三种亚型的织边。亚型 I 具有斜方辉石，但具有不同的微观结构，Mg# 与镁铁质岩中的斜方辉石不同；亚型 II 包含石榴石，其中包含许多矿物包裹体，尤其是钛铁矿，而硅铝矿主体中的石榴石几乎没有包裹体；亚型 III 缺乏斜方辉石或石榴石，但有丰富的磷灰石。显示斜长石成分从穿过织边的镁铁质岩浆进入透质岩的分布图表明，每个亚型的织边都有一个特征模式。根据其显微结构特征，在织边和寄主硅质岩中确定了四种类型的黑云母。(a) 残留的黑云母形成小的圆形红褐色颗粒，主要作为包晶堇青石中的包裹体和泛晶岩中的石榴石；(b) 镶边黑云母形成具有高尊重比的板状亚自形颗粒；(c) 硅藻土黑云母形成了硅藻土基质中常见的板状亚自面体颗粒；(d) 逆行黑云母，它部分替代了泛晶岩中的包晶堇青石和石榴石。这四组黑云母还通过其主要元素 (EMPA) 和微量元素 (LA-Q-ICP-MS) 组成进行区分。残余黑云母的 TiO2 含量高，Sc 和 S 含量低，而逆行黑云母的 Al2O3 含量高，但 Sc 和 Cr 含量低。镶边黑云母和硅质黑云母一般非常相似，但镶边黑云母的 Sc 和 S 含量较高。由显微 XRF 和 LA-Q-ICP-MS 分析构建的整个布边的全岩成分剖面显示：（a）Al2O3、FeO、MgO 和 CaO 都从穿过布边的镁铁质石蜡减少到硅藻土中；(b) Na2O 在镁铁质 scholle 中最低，通过织边上升并在进入硅质岩主体约 20-30 毫米处达到最大值；(c) K2O 在镁铁质 scholle 中最低，在织边的前半部分达到最高值，然后在达到较高但中间值之前下降，大约 20 毫米进入硅藻土。在微量元素中，Cs 和 Rb 的分布与 K2O 非常相似。