Title: MONAZITE-(Sm), A NEW MEMBER OF THE MONAZITE GROUP FROM THE ANNIE CLAIM #3 GRANITIC PEGMATITE, SOUTHEASTERN MANITOBA
Abstract: Monazite-(Sm) was found in the Annie Claim #3 pod of lepidolite-subtype granitic pegmatite within the Greer Lake intrusion of pegmatitic leucogranite, in the Archean Bird River Subprovince of the Superior Province, in southeastern Manitoba.It occurs as tabular crystals ≤0.4 mm in diameter, associated with manganocolumbite, quartz, albite and lithian muscovite.Monazite-(Sm) is yellowish, translucent, with a white streak, vitreous to greasy luster, and no observed fluorescence.One good cleavage is present, tenacity is brittle, and the fracture is uneven.Monazite-(Sm) has no observable pleochroism; ␣ 1.768 (5),  1.771(3), ␥ > 1.808(3); 2V meas 29(8)°, X = b, Z ٙ c = 9° ( obtuse).It is monoclinic, space group P2 1 /n; a refinement from single-crystal and powder (Gandolfi) X-ray-diffraction data gave a 6.725(1), 6.739( 3), b 6.936(1), 6.951(3), c 6.448(1), 6.462(3) Å,  104.02(1)°, 104.03(4)°,V 291.8(1), 293.6(2)Å 3 , Z = 4; D calc derived from average chemical composition is 5.512 and 5.478 g/cm 3 .The strongest six lines of the (Gandolfi) X-ray-diffraction pattern [d in Å(I)(hkl)] are: 4.647(5)(011), 4.164(8)( 111), 3.492(4)(111,020), 3.264(7)(200), 3.065(10)(120), and 2.857(9)( 112,012).The monazite-(Sm) contains, in wt.%, up to 14.29 Sm 2 O 3 , 13.48 Gd 2 O 3 and 6.28 Nd 2 O 3 , and moderate percentages of the huttonite and brabantite components.The most Sm-rich composition gives (Sm 0.197 Gd 0.179 Ce 0.148 Th 0.125 Ca 0.107 Nd 0.090 La 0.030 Y 0.030 Pr 0.023 Tb 0.017 Zr 0.017 Dy 0.016 Pb 0.016 U 0.002 ) ⌺0.997 (P 0.963 Si 0.044 ) ⌺1.007 O 4 .Adjustment of U and Th of the monazite-(Sm) to their original contents 2.64 Ga ago slightly improves the stoichiometry and proves that all the Pb present is radiogenic.The middle-REE-dominant signature of the Annie Claim #3 monazite-(Sm) is shared with the broadly associated Y(Ta,Nb)O 4 mineral (formanite?) and dysprosian xenotime-(Y); this exotic pattern of REE abundances is possibly generated by selective and differential complexing of REE in the granite-to-pegmatite sequence of solidification.