Manus basin

Central Manus Basin Vienna Woods (3° ID S, 150°17 E) 2500 2-km-wide axial rift graben of the northeast spreading center. Mostly massive pillow lava floor. Sulfide chimneys up to 20 m high are venting clear, milky and black fluids. Sulfate smokers are also present. Sphalerite, wurtzite, pyrite, marcasite, chalcopyrite, galena, amorphous silica, barite. Sulfate chimney anhydrite, silica, barite. 

Eastern Manus Basin Desmos cauldron (3 42 S, 151°52 E) 2000 Caldera of basalt/basaltic andesite at an intersection of a spreading center and a transform fault Sulfide ores were not recovered. Megaplume-like methane anomalies in water column over the caldera. Ferruginous oxide deposits. Pyrite and native sulfur disseminated in basaltic andesite. 

Eastern Manus Basin Pacmanus field (3°42 S, 151°42.6 E) 1650 Crest of a prominent ridge of dacite flows and domes called Pual Ridge which exists in pull-apart basin. 4-m-high sulfide chimneys venting smoke (no temperature information). Only one ore chip (1 cm) was recovered. Cohesive anhydrite, chalcopyrite, bomite, tennantite and sphalerite. 

No. Host Axial Seamount CASM 14 B North Fiji Basin 24 B Mariana Trough at 18 N 11 A Valu Fa, Lou Basin 47 B, A, D Eastern Manus Basin 26 D Jade Okinawa Trough 17 R... 

A few REE data on hydrothermal solutions are available (Fig. 2.34). Chondrite normalized REE patterns of hydrothermal solutions from Vienna Wood, Pacmanus and Desmos, Manus Basin exhibit positive Eu anomaly and LREE enrichment are similar to midoceanic ridge solution and Kuroko ore fluids. This positive Eu anomaly (Fig. 2.35) may have been caused by the selective leaking of Eu due to the interaction of an ascending hydrothermal solution and footwall volcanic rocks (Gena et al., 2001). It is interesting to note that altered basaltic andesite has a negative Eu anomaly and this feature is the same as that found in the Kuroko mine area (Shikazono, 1999). 

Site No. Name of site 1 Okinawa Trough JADE 2 Okinawa Trough CLAM 3 Okinawa Trough South Ensei 4 Izu-Bonin Suiyo SM. 5 Mid-Mariana Trough Alice Springs 6 South Mariana Trough Forecast vent 7 Manus Basin Vienna Woods 8 North Fiji Basin 9 Lau Basin Vai Lili... 

N Axial Seamount CASM 14 N. Fiji Basin 24 Mariana Trough at 18°N 11 Valu Fa, Lau Basin 47 Eastern Manus Basin 26 Jade, Okinawa Trough 17... 

Kerguelen xenolilhs O Samoa xenoHths 7 CamNoonline G Popping Rock Shooa/S.MAR e N Chile Ridge o Manus Basin... 

I Okinawa Trough Lau Basin Manus Basin Mariana Trough... 

Manus Basin is a back-arc basin located north of the New Britain island arc that consists of NE-SW trending ridge segments offset by transform faults. On the Manus Spreading Center in central Manus Basin the Vienna Woods hydrothermal field consists of a 300 m-diameter sulfide mound with an extensive foresf of active and inactive sphalerite-barite-rich, sulfide-sulfate-oxide chimneys up to 15 m-long atop it. Vent fluids from one of the active chimneys reach temperatures as high as 302°C. In the eastern Manus Basin, two important hydrothermal fields are known. The PACMANUS field includes discontinuous sulfide occurrences over a 3 by 0.8 km area and active venting of unknown nature. Volcanic rocks are andesitic to rhyodacitic. 

Mariana Trough. Manus Basin, North Fiji Basin,... 

Magellan Seamount 406 Manihiki Plateau 393 Manus Basin 459,470 Mariana Trough 470 Marianas back-arc 459,471 Maud Rise 40... 

Ra, respectively Moreira et al. 1995 Sarda et al. 2000), the Southwest Indian Ridge near Bouvet Island (14.9 Ra Kurz et al. 1998) and the Manus Basin back-arc spreading center (15.1 Ra Shaw et al. 2001). In each of these areas, the high He/ tae signal can be attributed to introduction of high He/ He material from a nearby mantle hotspot. The apparent upper limit to the measured He/ He in these cases is usually presumed to stem from dilution with ambient upper mantle having He/" He between 7 and 9 Ra. 

O Popping Rock Shona/SMAR N Chile Ridge O Manus Basin... 

Significant decoupling of He and Ne isotopes does appear to occur in some cases, and is best exemplified by the spreading ridge basalts from the Manus Basin (Shaw et al. 2001). Manus Basin basalts have He He ratios up to 15 Ra, yet they show a Ne isotope slope that is less than the MORB trend as defined by the popping rocks (Fig. 11). Shaw et al. (2001) considered several possible explanations for the discrepancy, ruling out crustal contamination, fluid addition from the subducting plate, or addition of Ne from ancient... 

Whereas the majority of the Manus Basin samples (particularly from the Manus Spreading Centre and the Extensional Transform Zone) are characterized by He/ He ratios greater than those of MORB, this is not the case for lavas from the Lau Basin or the North Fiji Basin. Indeed, a significant number of samples from both basins have... 

Figure 3. Neon isotope systematics of baek-are voleanism. Back-are data from Honda et al. 1993b (Lau Basin) Ikeda et al. 1998 and Sano et al. 1998a (Mariana Trough) and Shaw et al., 2001 (Manus Basin). Loihi-Kilauea (L-K) trend from Honda et al. (1991), Manus trend from Shaw et al. (2001). mfl = mass fractionation hne.

In contrast (again) to the helium isotope database, neon data in BABB are sparse. To date, neon isotope results are available for the Lau Basin (Honda et al. 1993b), the Mariana Trough (Ikeda et al. 1998 Sano et al. 1998a) and the Manus Basin (Shaw et al. 

The Manus Basin samples lie along a trajectory with a slope less than the MORB correlation line (the so-called Manus trend ). 

Maepherson CG, Hilton DR, Mattey DP, Sinton JM (2000) Evidence for an O-depleted mantle plume from contrasting ratios of back-arc lavas from the Manus Basin and Mariana Trough. Earth... 

Marly B, Sano Y, France-Lanord C (2001) Water-satnrated oceanic lavas from the Manus Basin volatile behavionr dnring assimilation-fractional ciystalhsation-degassing (AFCD). J Volcanol Geotherm Res 108 1-10... 

---