栾锂云母:锂云母系列的新成员

Luanshiweiite: A New Member of Lepidolite Series

新矿物栾锂云母[KLiAll.5口0．5（Si315A105）010（OH，F）2]发现于豫西卢氏县官坡镇稀有金属花岗伟晶岩密集区309号脉。其主要共／伴生矿物有石英、“栾锂云母的富氟类似物”、羟磷锂铝石、铯沸石、钽铋矿及贫Na、Ca但富Li、OH或F电气石等。其次有钽铁矿、钽锰矿、三锂云母、多硅锂云母（？）、细晶石族矿物、钠长石（An≤4）和锂辉石、氧钠细晶石及氟钙细晶石等细晶石族矿物；偶尔与白云母等共生。根据产出特征，借鉴相关成岩．成矿实验和流体包裹体研究成果，推测栾锂云母主要从一类低熔的富挥发份和活性组份，以及富亲石性成矿元素的岩浆．热液过渡流体中直接结晶所成。栾锂云母多呈鳞片状集合体产于309伟晶岩脉边缘带或／和其内的单矿物细脉中。其单个片径大都小于1naln。矿物具玻璃光泽，解理面显珍珠光泽；沿（001）面的解理极完全；显微硬度平均为102kg／mm2，约相当于摩氏硬度3；实测密度为2．851g，cm3，计算密度值2．868g／cm3。正延性，二轴晶，负光性，2V=36°～40°；折光率：札=1．5474，Nm=1．5700，M=1．5729。光性定位：Np=X=c，Nm=Y=b，Ng=Z=a。矿物大都发育波状消光。化学成分（wB/％）Si0251．65，Ti020．01．A120323．50，FeO0．72，CaO0．02，MnO0．22，MgOO．04，Na200．15，K2011．62，Li203．80，Rb200．78，Cs200．53，F3．85，H20＋2．82，F=O.1．62，合计98．09．％。根据O＋OH＋F=12apfu，计算的经验化学式为（K1.01Rb0.03Cs0.02Na0．02∑1．08（Li1.04A1.39Fe0.04Mn0.0lb48（Si351Al0.49）∑4．00（09890Ho11）∑10.00（OH1.17F0.83）∑200。简化式：KLiAll．5口0．5（Si35A10．5）010（OH，F）2，理想化学式为KLiAlls口0．5（Si3.5A10．5）010（OH）2。与沃洛欣云母RbLiAll5口0.5（Si3.5A10．5）4010F2比较，新成员是沃洛欣云母间阳离子的钾类似物，以及附加阴离子的羟占优的类似物。栾锂云母晶体结构的精测显示，矿物属单斜晶系，空间群C2／c。晶胞参数：α=O．51861（7）nm，6=O．89857（13）nm，c=1．9970（3）nm，V=O．9265（2）nm3；β95．420（3）°，Z=4。栾锂云母为2蝎多型。其晶体结构精测的R因子僻1=0．098）欠佳，是由于矿物生成后，受到构造干扰所致。栾锂云母（Luanshiweiite）的命名旨在纪念我国知名的伟晶岩石学家栾世伟教授（1928～2012）。新矿物及其命名，业已得到IMACNMNC批准（批准文号IMA2011-102）。栾锂云母的原型标本典藏在北京中国地质博物馆内（注册号：M11797）。

A new mineral luanshiweiite, KLiAll.5口10.5（Si3.5A10.5）O10（OH,F）2, was found in No.309 rare-metal granitic pegmatite dike, located in closely spaced region of the pegmatites in Guonpo town, Lushi country, Henan Province, China （33°52.480＇N, 110°42.760＇E）. The mineral is closely associated with quartz, a ＂F-dominant analog of luanshiweiite＂, montebrasite, pollucite and bismutotantalite as well as Na-, and Ca-poor but Li-, and OH- or F-rich tourmaline etc.; secondly, it is associated with microlite group minerals including tantalite, tantalite-Mn, trilithionite, polylithionite（？）, microlite group minerals, albite （An〈4）, spodumene and oxynatromicrolite, fluorcalciomicrolite ere, and occasionally muscovite etc. According to the occurrence features of luanshiweiite, it may be suggested that luanshiweiite is crystallized basically from a subsolvus volatile- and flux-rich acid magma-hydrothermal transition fluid directly. The mineral occurs typically in scale aggregate in the polymineralic edge zone or/and in monomineralic veinlents in other zones in No.309 dike. Most individual grains of luanshiweiite are less than 1 mm2. Cleavage is {001} perfect. The scales are flexible. Micro-indentation is 102kg/mm2, Mohs ≈3. D （means.）= 2.851 g/mm3; D （talc.）= 2.868 g/mm3. Optically biaxial （-）, 2V=36°-40°, Np=1.5474, Nm=1.5700, Ng=1.5729. Orientation： Np=X=c, Nm=Y=b, Ng=Z=α. Luanshiweiite has widely wavy extinction. Chemical composition of the mineral （EPMA, averaged for 25 analyses; Li, Rb and Cs were determined by atom absorption spectra; F and 1-120＋ were determined by wet analyses. Recently, the wet F content has been examined by EPMA, and H20＋ content was calculated isochemically, which shows that the wet values are feasible ） is： SiO2 51.65, TiO20.O1,AIaO323.50, FeO0.72, CaO0.02, MnO0.22, MgO0.04, Na200.15, K20 11.62, Li203.80, Rb20 0.78, Cs20 0.53, F 3.85, 1-120＋2.82, F-=O- 1.62, total 98.09%. On the basis of O＋OH＋F =12 and OH＋F=2 apfu, the empirical formula is： （Kl.0lmb0.03Cs0.02Na0.02）∑l.O8 （Lil.04All.39Fe0.04 mn0.0l）∑2.48 （Si3.51A10.49） rA.00（O9.89 OHo.H）∑10.00（OHl.17F0,83）∑2.00. The simple formula is： KLiAll.5口0.5 （Si3.5Al0.5）O10 （OH,F）2, and the ideal Formula is： KLiA1L5口0.5（Si3.sAl0.5）O10（OH）2. In contrast with voloshinite, RbLIAILs口0.5（Si3.5 Al0.5）4.0O10F2, luanshiweiite is the potassium analog at the interstratified cations and OH-dominant analog at the attached anion site of voloshinite. From the structural refinement of the mineral, luanshiweiite is monoclinic, space group C2/c, unit-cell dimension： a=0.51861（7） urn, b=0.89857（3） rim, c=1.9970（3） urn, fl=95.42°, V=0.9265nm3, Z=4, polytype 2M1. The reason behind non-ideal structural refinement factor （R1 =0.098） is that the mineral was troubled by the tectogenesis. The mineral was named in honor of the known Chinese pegmatitic petrologist Prof. Luanshiwei （1928-2012）. Type material has been deposited in the Geological Museum of China, Beijing （Registration number is M 11797）.