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U-Pb geochronologic and mineral-chemical results from apatite and titanite in the Clarence Stream gold-antimony deposit, southwestern New Brunswick, Canada.

The Clarence Stream deposit in southwestern New Brunswick consists of several antimony-bearing gold mineralized zones hosted within large-scale structures in metasedimentary and metavolcanic sequences of the Cookson and Mascarene groups, as well as several younger magmatic intrusive rocks, consisting of gabbroic and intermediate dykes, and granitic pegmatite-aplite dykes. Mineral chemistry and U-Pb geochronology of apatite and titanite in the South, George Murphy, Richard, and Jubilee zones reveal details about the mineralizing fluids and timing of mineralization. Hydrothermal apatite and titanite hosted in mineralized quartz veins were analyzed by in situ methods including microX-ray Fluorescence Spectrometry ([mu]XRF) followed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS).

The apatite chondrite-normalized REE plots illustrate LREEN and HREEN enrichment (0.95, 2.08) and depletion (0.61, 1.94) patterns, pronounced negative ([(Eu/Eu*).sub.N], <0.80) and positive Eu anomalies ([(Eu/Eu*).sub.N], >0.82), in the South (CS332-264.5), Richard (BL12-117.5), and one of the Jubilee zone samples (BL43-74.2). These different REE patterns show that the apatite formed during two different stages from hydrothermal fluids under reducing to oxidizing environments. Apatite within the George Murphy Zone sample (CL33-247.25) shows [(LREE/HREE).sub.N] of 0.33 with negative Eu anomalies ([(Eu/Eu*).sub.N], <0.65), corresponding to crystallization in a reduced environment. The second sample from the Jubilee Zone (BL19-44-303) shows [(LREE/HREE).sub.N] of 0.73 with a positive Eu anomaly ([(EU/EU*).SUB.N]> >0.98), which formed in an oxidized environment. As the George Murphy, Richard, and Jubilee zones are hosted within the same structure, their combined U-Pb age is 374 [+ or - ] 24 Ma.

Two mafic intrusive rocks from the West (CS13-329-14.8) and South (CS17-353-127) subzones of the South Zone contain hydrothermal titanite. The chondrite-normalized REE plots in CS13-329-14.8 illustrate [LREE.sub.N]-depletion ([(LREE/HREE).sub.N], 0.18) with positive Eu anomalies ([(Eu/Eu*)].sub.N], >1.29) reflecting crystallization from a low oxygen fugacity fluid. However, CS17-353-127 shows [LREE.sub.N]-enrichment ([(LREE/HREE).sub.N], 1.24) with positive to negative Eu anomalies ([(Eu/Eu*).sub.N], 2.40-0.61). These positive to negative Eu anomalies could be representative of fluctuations from low to high oxygen fugacity of the mineralizing fluid; combined U-Pb geochronology results from these two samples yielded an age of 396.9 [+ or - ] 2.5 Ma.

Based on previous studies, the age of gold mineralization associated with the late phase of the Magaguadavic Granite is 396.0 [+ or - ] 0.5 Ma at the South Zone, which is confirmed by U-Pb geochronologic data from hydrothermal titanite. The maximum age from apatite shows that the gold mineralization at the George Murphy, Richard, and Jubilee zones is no older than the mineralization at the South Zone.

HASSAN HEIDARIAN (1), DAVID R. LENTZ (1), CHRISTOPHER R.M. MCFARLANE (1), AND KATHLEEN THORNE (2)

1. Department of Earth Sciences, University of New Brunswick, Eredericton, New Brunswick E3B 5A3, Canada <ha.heidarian@unb.ca>;

2. Geological Surveys Branch, New Brunswick Department of Energy and Resource Development, Eredericton, New Brunswick E3B 5H1, Canada

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Author:Heidarian, Hassan; Lentz, David R.; McFarlane, Christopher R.M.; Thorne, Kathleen
Publication:Atlantic Geology
Geographic Code:1CNBR
Date:Jan 1, 2021
Words:451
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