排序方式： 共有13条查询结果，搜索用时 31 毫秒
1.
Simon J. Meldrum Romeo S. Aquino Rene I. Gonzales Robert J. Burke Artha Suyadi Bambang Irianto Donald S. Clarke 《Journal of Geochemical Exploration》1994,50(1-3)
The Batu Hijau porphyry Cu---Au deposit lies in southwest Sumbawa Island, Indonesia. It is a world-class porphyry Cu deposit in an island are setting, and is typical of this deposit type in most features, including igneous association, morphology, hydrothermal alteration and mineralisation style.The region was not previously recognised as a porphyry Cu province; disseminated Cu sulphides were first recognised in float samples in southwest Sumbawa in 1987. Associated stream sediment sampling identified a broad area of anomalous Au and Cu in an area of greater than 5 km2 around Batu Hijau, including 169 ppb Au in BLEG samples and 580 ppm Cu in stream silts 1 km from the deposit. Mineralisation in bedrock at surface contains > 0.1 wt % Cu and > 0.1 ppm Au over an area of 0.6 km × 1.2 km, including a zone 300 m × 900 m containing > 0.3 wt % Cu. Areas with elevated Mo (> 30 ppm) form a distinctive annulus around this Cu-rich zone.Batu Hijau mineralisation is hosted in a tonalite intrusive complex, and diorite and metavolcanic wallrocks. There are no post-mineralisation igneous intrusions or breccia pipes within the deposit. The main tonalite intrusion forms a stock in the centre of the deposit, where it generally displays intensely pervasive potassic (biotite with magnetite-quartz) alteration and hosts most of the higher grade mineralisation. Younger tonalite dykes intruding the centre of this stock are generally less altered and mineralised than the older tonalite.The core zone of potassic alteration grades outward into extensive propylitic alteration (chlorite-epidote), with both variably overprinted by widespread fracture controlled intermediate argillic alteration (sericite-chlorite), and minor phyllic (sericite-pyrite) and sodic (albite) alteration. Argillic (sericite-kaolinite) and advanced argillic (kaolinite-alunite-pyrophyllite) assemblages occur near surface.Copper and Au grades within the orebody show a positive correlation with quartz stockwork intensity, although disseminated Cu sulphides are also common. Chalcopyrite and bornite are the principle hypogenal minerals, with minor chalcocite. Oxidation extends to a depth of 5 m to 85 m below surface across the deposit, and is underlain by weak supergene mineralisation. Drill testing of the deposit down to 650 m below surface reveals a single cylindrical to conical orebody of 334 million tonnes grading 0.8 wt % Cu and 0.69 gm per tonne Au; the depth extent of mineralisation is unknown. 相似文献
2.
Jenny E. Goldstein Laura Graham Sofyan Ansori Yenni Vetrita Andri Thomas Grahame Applegate Andrew P. Vayda Bambang H. Saharjo Mark A. Cochrane 《Singapore journal of tropical geography》2020,41(2):190-208
Near-annual landscape-scale fires in Indonesia's peatlands have caused severe air pollution, economic losses, and health impacts for millions of Southeast Asia residents. While the extent of fires across the peatland surface has been widely attributed to widespread peatland drainage for plantation agriculture, fires that transition from surface into sub-surface soil-based fires are the source of the most dangerous air pollution. Yet the mechanisms by which this transition occurs have rarely been considered, particularly in diversely managed landscapes. Integrating physical geography methods, including active fire scene evaluations and hydrological monitoring, with qualitative methods such as retrospective fire scene evaluations and semi-structured interviews, this article discusses how and why sub-surface peat fire transition occurs in an intensively altered peatland ecosystem in Indonesia's Central Kalimantan province. We demonstrate that variable water table levels and flammable surface vegetation (fire fuels) are co-produced socio-political and biophysical phenomena that enable the conditions in which surface fire is likely to transition into peat fire and increase landscape vulnerability to ongoing, uncontrollable annual fires. This localized understanding of peat fire transition counters normative causal narratives of tropical fire such as ‘slash-and-burn’, with implications for the management of new fire regimes in inhabited landscapes. 相似文献
3.
Attribution of changes in the water balance of a tropical catchment to land use change using the SWAT model 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 Changes in the water balance of the Samin catchment (277.9 km2) on Java, Indonesia, can be attributed to land use change using the Soil Water Assessment Tool model. A baseline‐altered method was used in which the simulation period 1990–2013 was divided into 4 equal periods to represent baseline conditions (1990–1995) and altered land use conditions (1996–2001, 2002–2007, and 2008–2013). Land use maps for 1994, 2000, 2006, and 2013 were acquired from satellite images. A Soil Water Assessment Tool model was calibrated for the baseline period and applied to the altered periods with and without land use change. Incorporating land use change resulted in a Nash–Sutcliffe efficiency of 0.7 compared to 0.6 when land use change is ignored. In addition, the model performance for simulations without land use change gradually decreased with time. Land use change appeared to be the important driver for changes in the water balance. The main land use changes during 1994–2013 are a decrease in forest area from 48.7% to 16.9%, an increase in agriculture area from 39.2% to 45.4%, and an increase in settlement area from 9.8% to 34.3%. For the catchment, this resulted in an increase of the runoff coefficient from 35.7% to 44.6% and a decrease in the ratio of evapotranspiration to rainfall from 60% to 54.8%. More pronounced changes can be observed for the ratio of surface runoff to stream flow (increase from 26.6% to 37.5%) and the ratio of base flow to stream flow (decrease from 40% to 31.1%), whereas changes in the ratio of lateral flow to stream flow were minor (decrease from 33.4% to 31.4%). At sub‐catchment level, the effect of land use changes on the water balance varied in different sub‐catchments depending on the scale of changes in forest and settlement area. 相似文献
4.
5.
Nineteen benthonic and planktonic foraminiferal zones and their subzones have been recognized in the Tethyan cretaceous successions along the four sections analyzed in the northwestern Zagros fold–thrust belt within the preforeland–foreland basin. A detailed micropaleontological investigation revealed eight benthonic zones from the Qamchuqa Formation (Barremian to Lower Early Cenomanian) including: the Choffatella decipiens interval zone, C. decipiens/Palorbitolina lenticularis total range zone, C. decipiens/Salpingoporella dinarica interval zone, Mesorbitolina texana total range zone, Mesorbitolina subconcava total range zone, Orbitolina qatarica total range zone, Orbitolina sefini total range zone, and the Orbitolina concava partial range zone. The Rotalipora cushmani total range zone was recorded in the Dokan Formation that overlies the Qamchuqa Formation of the Late Cenomanian age. The Gulneri Formation is represented only by the Whitnella archaeocretacea partial range zone/Heterohelix moremani total range subzone and indicates the Late Cenomanian/Early Turonian age. Six planktonic foraminiferal zones were recorded from the Kometan Formation, indicating the Late Cenomanian to Early Campanian age, and are represented by the R. cushmani/H. moremani subzone, Helvetotruncana helvetica total range zone, Marginotruncana sigali partial range zone, Dicarinella primitiva interval range zone, Dicarinella concavata interval zone, Dicarinella assymetrica total range zone, and Globotruncanita elevata partial range zone. Two planktonic foraminferal zones were recorded also and these are related to the Globotruncana (fornicata, stuartiformis, elevata, and ventricosa) assemblage zone, Globotruncana calcarata total range subzone, from the Shiranish Formation, Lower Late Campanian, while the second zone is nominated as the Globotruncana (arca, tricarinata, esnehensis, and bahijae) assemblage zone, Globotruncana gansseri interval subzone, and Globotruncana contusa total range zone of the Late Campanian to basal middle Maastrichtian age. The last zone is related to the Abathomphalus mayaroensis partial range zone (of Late Maastrichtian age) and occasionally intercalated with the Orbitoides–Loftusia benthic zones. An important hiatus, between the Qamchuqa and Kometan formations was proved and manifests Pre-Aruma unconformity, and is occasionally associated with the global Cenomanian–Turonian Oceanic Anoxic Euxinic Event, while the Maastrichtian red bed of the Shiranish Formations mostly points to Tethyan upper Cretaceous Oceanic Red Bed. 相似文献
6.
Nerilie J. Abram Helen V. McGregor Michael K. Gagan Wahyoe S. Hantoro Bambang W. Suwargadi 《Quaternary Science Reviews》2009,28(25-26):2794-2803
The Indo-Pacific Warm Pool (IPWP) is thought to play a key role in the propagation and amplification of climate changes through its influence on the global distribution of heat and water vapour. However, little is known about past changes in the size and position of the IPWP. In this study, we use a total of 48 modern and fossil coral records from the Mentawai Islands (Sumatra, Indonesia) and Muschu/Koil Islands (Papua New Guinea) to reconstruct oscillations in the extent of the IPWP since the mid-Holocene. We show that reliable estimates of mean sea surface temperature (SST) can be obtained from fossil corals by using low-resolution Sr/Ca analysis of a suite of corals to overcome the large uncertainties associated with mean Sr/Ca-SST estimates from individual coral colonies. The coral records indicate that the southeastern and southwestern margins of the IPWP were cooler than at present between 5500 and 4300 years BP (1.2 °C ± 0.3 °C) and were similarly cool before 6800 years BP. This mid-Holocene cooling was punctuated by an abrupt, short-lived shift to mean SSTs that were warmer than at present between 6600 and 6300 years BP (1.3 °C ± 0.3 °C), while similarly warm conditions may have also existed after 4300 years BP. We suggest that mid-Holocene cooling at our study sites was related to contractions of the southeastern and southwestern margins of the IPWP, associated with the more northerly position of the Inter-tropical Convergence Zone (ITCZ) that accompanied mid-Holocene strengthening of the Asian summer monsoon. Conversely, intervals of abrupt warming appear to correspond with widespread episodes of monsoon weakening and accompanying southward migrations of the ITCZ that caused the IPWP to expand beyond our coral sites. Intervals of a strengthened Asian monsoon and cooling in the southwestern IPWP during the mid-Holocene appear to correspond with a more positive Indian Ocean Dipole (IOD)-like mean configuration across the tropical Indian Ocean, suggesting that the Asian monsoon–IOD interaction that exists at interannual time scales also persists over centennial to millennial scales. Associated mean changes in the Pacific ENSO modes may have also occurred during the mid-Holocene. The dynamic and inter-connected behaviour of the IPWP with tropical climate systems during the mid-Holocene highlights the fundamental importance of the warm pool region for understanding climate change throughout the tropics and beyond. 相似文献
7.
Bambang P. Istadi Gatot H. Pramono Prihadi Sumintadireja Syamsu Alam 《Marine and Petroleum Geology》2009
The mud volcano known as LUSI first erupted in May 2006 in East Java, Indonesia. The eruption has continued for over two years, and potentially will continue for many years to come, impacting an ever larger area. An obvious and significant question is how extensive the impacted area will become in the coming years. The answer is important for planning scenarios for the relocation of people and infrastructure and for managing the environment and economy. To make such a prediction, an understanding of the geological processes controlling the mud volcanic evolution is needed. 相似文献
8.
正常而言，在印度尼西亚的苏门答腊和加里曼丹岛，即使在非厄尔尼诺年，每年6月或7月的旱季会出现烟雾问题。研究发现，近年来烟雾问题并不仅仅出现在旱季，雨季也有发生。进一步的观测和野外调研表明，这些烟雾来源于用火烧的方式进行油棕榈及其它林木种植前的土地整理，然而这种方式早已被完全禁止。结果，这两个省的绝大多数的水灾灾区位于这些植被被焚毁的地区。 相似文献
9.
10.
Jean-Claude Thouret Franck Lavigne Hiroshi Suwa Bambang Sukatja Surono 《Bulletin of Volcanology》2007,70(2):221-244
Mt. Semeru, the highest mountain in Java (3,676 m), is one of the few persistently active composite volcanoes on Earth, with
a plain supporting about 1 million people. We present the geology of the edifice, review its historical eruptive activity,
and assess hazards posed by the current activity, highlighting the lahar threat. The composite andesite cone of Semeru results
from the growth of two edifices: the Mahameru ‘old’ Semeru and the Seloko ‘young’ Semeru. On the SE flank of the summit cone,
a N130-trending scar, branched on the active Jonggring-Seloko vent, is the current pathway for rockslides and pyroclastic
flows produced by dome growth. The eruptive activity, recorded since 1818, shows three styles: (1) The persistent vulcanian
and phreatomagmatic regime consists of short-lived eruption columns several times a day; (2) increase in activity every 5
to 7 years produces several kilometer-high eruption columns, ballistic bombs and thick tephra fall around the vent, and ash
fall 40 km downwind. Dome extrusion in the vent and subsequent collapses produce block-and-ash flows that travel toward the
SE as far as 11 km from the summit; and (3) flank lava flows erupted on the lower SE and E flanks in 1895 and in 1941–1942.
Pyroclastic flows recur every 5 years on average while large-scale lahars exceeding 5 million m3 each have occurred at least five times since 1884. Lumajang, a city home to 85,000 people located 35 km E of the summit,
was devastated by lahars in 1909. In 2000, the catchment of the Curah Lengkong River on the ESE flank shows an annual sediment
yield of 2.7 × 105 m3 km−2 and a denudation rate of 4 105 t km−2 yr−1, comparable with values reported at other active composite cones in wet environment. Unlike catchments affected by high magnitude
eruptions, sediment yield at Mt. Semeru, however, does not decline drastically within the first post-eruption years. This
is due to the daily supply of pyroclastic debris shed over the summit cone, which is remobilised by runoff during the rainy
season. Three hazard-prone areas are delineated at Mt. Semeru: (1) a triangle-shaped area open toward the SE has been frequently
swept by dome-collapse avalanches and pyroclastic flows; (2) the S and SE valleys convey tens of rain-triggered lahars each
year within a distance of 20 km toward the ring plain; (3) valleys 25 km S, SE, and the ring plain 35 km E toward Lumajang
can be affected by debris avalanches and debris flows if the steep-sided summit cone fails. 相似文献