Paleomagnetic conglomerate tests were run at three localities in the Conglomerate formation of the Jurassic Laberge Group in the southern Yukon. The localities are located within the Whitehorse Trough about 5, 20 and 40 km east of its margin with the intruded Coast Plutonic Complex. At each locality, 2.5-cm-diameter cores were drilled from 32 clasts of mainly igneous provenance and 8 more from the conglomerate matrix, totaling 120 cores, and yielding 190 specimens in all. The specimens were analysed using standard paleomagnetic demagnetization and testing techniques. The matrix, mostly greywacke in composition, yields characteristic remanent magnetization (ChRM) directions carried by pyrrhotite that give coherent steep downward directions. The clasts, at all three localities, yield paleomagnetic conglomerate tests that show statistically random ChRM directions. This leads to the conclusion that the clasts were not remagnetized by the event that remagnetized the matrix, which was likely caused by hydrothermal fluid flow during the Late Cretaceous to Eocene Laramide Orogeny. Furthermore, these conclusions support earlier studies by demonstrating that felsic plutons in the Whitehorse Trough likely carry primary ChRM directions, e.g., the 75 Ma Mount Lorne stock, the 109 Ma Mount McIntyre pluton, the 112 Ma Whitehorse batholith, and the 186 Ma Teslin Crossing stock.

The Mount M'Clintock map area, northeast of Whitehorse, is dominated by Middle Triassic to Jurassic sedimentary and volcanic strata of Stikinia with small portions of the Cache Creek and Yukon-Tanana Terranes. These assemblages were deformed prior to the mid-Cretaceous intrusion of three plutonic suites and the deposition of two suites of volcanic rocks. Sedimentary rocks previously mapped as undifferentiated Lewes River and Laberge Group strata are separated into their respectve groups and further sub-divided into several members. Lewes River Group rocks form three units that are Carnian and older, Norian, and Upper Norian in age and are represented by siliceous siltstone and calcareous sandstone, conglomerate and limestone respectively. Laberge Group strata are divided according to lithology and dominated by siltstone-sandstone couplets and massive siltstone with lesser conglomerate and volcanogenic sandstone. Volcanic rocks previously mapped as Hutshi Group are divided into the dominantly mafic and submarine, MiddleTriassic Joe Mountain volcanic complex (JMVC) and the dominantly felsic and sub-aerial Mount Byng volcanic complex (BCVC). The volcanic and sedimentary rocks generally increase in age from Middle Triassic to Jurassic from west to east across the map area. Plutons cutting these strata belong to the M'Clintock Lakes (120 Ma), the Whitehorse (115 Ma), and the Mount McIntyre (109 Ma) plutonic suites. The predominantly felsic fragmental rocks of the BCVC are genetically associated with the Byng Creek pluton of the Mount McIntyre plutonic suite. The BCVC is nested into the country rocks and its eastern margin and is preserved as the rim of a tilted caldera. Strata of the Laberge and Lewes River groups are folded throughout. Wavelengths are on the order of approximately 1-2 km, but are much tigter in black siltstone units and adjacent to northwest-trending faults. Faults are ubiquitous throughout the map area and form three sets. North-trending faults are the most common. They are spaced a few kilometres from each other and dictate the physiography and drainage of the region. Northwest-trending faults, in the northeastern corner of the map area control the Teslin River valley and juxtapose Yukon-Tanana rocks with Stikinia. Older faults are dominantly east-trending but are terminated or reactivated by younger faults. Copper (gold-molybdenum-tungsten) skarns and gold-bearing quartz veins are the two mineral deposit types most likely to be discovered in the map area. The source of the placer gold in Sheldon Creek is unknown but may be related to gold veins in the JMVC, BCVC, Sheldon Creek volcanics or the surrounding sedimentary rocks. Hydrothermal activity in the JMVC is characterized by orange weathering alteration, breccias, and carbonate veins. Cache Creek rocks in the southern part of the map area are targets for listwaenite associated gold veins.

The geology in the Mount Nansen area, of the Dawson Range, comprises a metamorphic basement overlain and intruded by mid and Late Cretaceous magmatic rocks. Mid-Cretaceous epithermal deposits are recognized in the Brown-McDade cluster in the south, and Late Cretaceous porphyry and epithermal occurrences in the centrally located Klaza cluster. Here we report eight new U-Pb zircon crystallization ages, two CA-TIMS and six LA-ICPMS, and Pb isotopic data for igneous feldspar from six samples. A 199.06 ± 0.96 Ma crystallization age demonstrates the host rock to the Brown-McDade deposit is the Late Triassic to Early Jurassic Minto suite. We report crystallization ages of 111 ± 1.8 Ma for the Dickson Hill porphyry, 107.96 ± 0.03 and 107.86 ± 0.03 Ma for the central and border phases of the Bow Creek granite, respectively, and 107.0 ± 0.72, 107.0 ± 0.78 and 107.5 ± 0.67 Ma for equigranular and porphyritic phases of the Dawson Range granodiorite. These ages confirm a mid-Cretaceous Whitehorse suite affinity for these rocks with porphyritic textures suggesting high-level emplacement. Feldspar Pb isotopic data of igneous rocks in the Mount Nansen area become more radiogenic with time and are distinct for Late Triassic to Early Jurassic plutonic rocks versus Cretaceous rocks. Cretaceous feldspar isotopic data broadly overlaps Pb isotopic values of galena from deposits throughout the Dawson Range suggesting coeval magmatic rocks are a significant source of metals.

Paleomagnetic results are presented for 154 specimens from 16 sites in the Late Cretaceous Seymour Creek stock, a small granodioritic intrusion emplaced into Paleozoic gneisses and schists of the Yukon-Tanana Terrane (YTT), west-central Yukon. Stepwise demagnetization of the specimens revealed steep characteristic remanent magnetization directions in 2 normal- and 14 reversed-polarity sites with a mean direction of declination D=65.0°, inclination I =-83.6° (alpha 95 = 4.3°, k =73.8). Geological relations suggest that the stock has not been tilted since its emplacement at 68.5 ± 0.2 Ma. The paleopole for the Seymour Creek stock at 55.2°N, 202.5°E (dp =8.3°, dm=8.5°), plots south of the North American apparent polar wander path. This suggests that the YTT has experienced a net 79° ± 36° counter-clockwise rotation, and a nonsignificant 2.4° ± 7.5° anti-poleward translation relative to North America since 68.5 Ma. This result does not agree with the previously reported large poleward translation and minimal rotation estimated for the YTT from paleomagnetism of the coeval Carmacks Group volcanic rocks.

Two distinct but undeformed suites of granitic plutons intrude deformed siliciclastic rocks in western Dorsey Terrane. A calc-alkaline hornblende-bearing gabbro to granodiorite stock has been dated at 181.5 Ma (by the Rb/Sr method). The second suite consists of highly evolved late-orogenic granites of the Thirtymile stock and Hake Batholith, which are approximately 100 Ma. The penetrative fabric of the metasedimentary rocks indicates generally eastward-vergent layer-parallel shear. The deformation of the siliciclastic rocks is thus constrained at older than 181 Ma. The absence of resetting of the Rb-Sr isotopic ratios of the Jurassic pluton indicates that the mid-Cretaceous magmatism was emplaced at a shallow crustal depth. Since the Jurassic pluton has both a 'juvenile' Sr isotopic ratio of 0.7045 and chemistry indicative of a largely mantle-derived source, a subduction-related setting for magma generation is likely. The spatial relationship of craton-derived clastic rocks and these plutons requires that subduction had an eastward polarity.

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Paleomagnetic and geobarometric results are reported here for the Early Jurassic Granite Mountain batholith, an ~600 km² granodiorite intrusion in the Yukon-Tanana Terrane. Paleomagnetic analyses of 331 specimens from 24 sites yield magnetite-borne characteristic remanent magnetization (ChRM) directions. Eight northerly and westerly sites display a mean direction A (D=337, I=69°; a 95 =7.6°, k=54). Another 11 sites appear to be lightning-struck, or exhibit unstable remanence, and 3 sites in a fault-bounded block to the southeast carry an anomalous northeast upwards ChRM direction B. Two sites in a Cretaceous andesite porphyry dyke and its contact zone give a westerly, steep-down ChRM direction, C. Aluminum-in-hornblende geobarometry at 10 sites defines emplacement depths of ~16 km in the north and west, and ~19 km in the southeast. The batholith has probably not been significantly tilted since its emplacement, but it may be subdivided into two separate intrusive phases or structural blocks that have experienced differential uplift. Ambient temperatures at 16-19 km were too high for magnetite to record an enduring remanence, so the observed ChRMs likely record uplift of the batholith through ~15 km depth, at 180-170 Ma. Both A and C ChRM directions are similar to those expected for Early Jurassic and Late Cretaceous reference poles, respectively, suggesting that the Yukon-Tanana Terrane is not far-traveled with respect to cratonic North America since Early Jurassic time.

This Atlas presents an extensive geoscience data set for the Late Triassic to Jurassic plutons that intrude the Intermontane terranes in Yukon. Plutons of this age are associated with significant porphyry Cu ± Au ± Mo deposits in British Columbia. In Yukon, Cu–Au–Ag deposits at Minto and Carmacks Copper are hosted by an Early Jurassic batholith but are not typical porphyry deposits. This project aims to provide the regional framework for Late Triassic to Jurassic plutons and associated mineral occurrences in southern Yukon. We systematically describe over 34 plutons and present new data for most of these, including 47 U-Pb zircon dates, 44 Ar-Ar dates, 187 whole-rock geochemical analyses, 30 whole-rock Sr and Nd isotope analyses, 27 feldspar Pb isotope analyses, zircon Hf isotope analyses for 22 samples and 26 pressure estimates from aluminum-in-hornblende analyses. Complementing these analytical data are extensive photomicrographs, photographs and maps.

The Joe Mountain map area, northeast of Whitehorse, is underlain by folded, Upper Triassic and Jurassic sedimentary and volcanic strata of the Whitehorse Trough which are intruded by north-trending Cretaceous plutons. Volcanic rocks previously mapped as ""Volcanics of uncertain age"" and Hutshi Group are Triassic in age and comprise three mappable units dominated by thick accumulations of basaltic and andesitic, aphyric pillowed volcanics. The volcanics, and associated sedimentary rocks dominate the eastern part of the map area whereas a thick carbonate assemblage dominates the Upper Triassic stratigraphy in the western part of the map area. The east-west transition represents either a sharp facies change across the map area or a structural juxtaposition. Numerous through-going, north-trending faults which cut the region may originate from motion along the interpreted Lake Laberge Fault Zone which underlies the Yukon River/Lake Laberge valley. Potential mineral deposits in this map area include copper (gold-molybdenum-tungsten) skarns and gold-bearing quartz veins. Regional silt geochemistry indicates that the distribution of the Triassic volcanic suites is spatially coincident with regionally extensive, gold-in-silt anomalies. The source of these anomalies is uncertain and provide for intriguing prospecting targets.