Zamboanga Del Norte Research Articles

Intestinal Capillariasis, Western Mindanao, the Philippines

To the Editor: Capillariasis is caused by the foodborne nematode Capillaria philippinensis. Infection causes severe diarrhea and protein loss resulting in dehydration, cachexia, and eventually death. Infected patients may also have borborygmi, abdominal pain, weight loss, anorexia, vomiting, and bipedal edema (1). C. philippinensis was first reported in 1963 in Bacarra, Ilocos Norte Province in the northern Philippines (2). Since then, additional endemic foci of C. philippinensis have been identified. The most recent focus is in Monkayo, Compostela Valley, in the southern Philippines (3). In the past several years, suspected unconfirmed cases have been reported from Zamboanga del Norte Province in western Mindanao. In 1999, an epidemic of gastroenteritis in Pinan Municipality was reported; it resulted in 42 deaths. The schistosomiasis team of the Department of Health Regional Office conducted stool examinations and suspected the presence of Capillaria ova in symptomatic patients (4). In November 2007, several deaths caused by chronic diarrhea were reported in Siayan Municipality. These deaths were attributed to capillariasis, but their cause was never confirmed (5). In February 2008, we obtained 205 stool specimens from residents of Katipunan who had a history of diarrhea of >2 weeks duration and abdominal disturbance. These samples were processed by using the formalin–ether concentration technique (6) and examined by expert microscopists. One hundred fifty-one (73.3%) persons were infected with >1 organism; 67 (32.5%) had 1 parasitic infection and 84 (40.8%) had multiple parasitic infections. Ninety-one (44.2%) persons had >1 soil-transmitted helminth infection, and 93 (45.2%) had >1 protozoan infection. Ten (4.9%) persons were confirmed to have Capillaria infections. The distribution of organisms observed is shown in the Table. Table Parasites detected in Katipunan, Zamboanga del Norte, the Philippines, February 2008* Among the 10 persons who had capillariasis, 8 were from Barangay (smallest adminstrative region) Matam, 1 from Barangay Dabiak, and 1 from Barangay Carupay, a nearby barangay. Six cases were in male patients and 4 were in female patients. Ages of infected persons ranged from 5 to 54 years (mean 29.2 years, SD 17.1 years). Three of the reported case-patients (a 5-year-old boy, an 8-year old boy, and a 48-year-old woman) were from the same household. A total of 24 persons in Katipunan were interviewed regarding history of capillariasis and their eating habits. Fourteen residents reported having eaten kinilaw (raw freshwater fish soaked in vinegar and garnished with salt, ginger, and lime). Seven of the persons interviewed had a diagnosis of capillariasis, and 6 had >1 relative with a diagnosis of capillariasis. All of the previously diagnosed case-patients were treated with albendazole (400 mg tablets). Most patients were instructed to take 1 tablet 1×/day for 20 days; others were instructed to take 1 tablet 2×/day for 5 or 10 days. The drug of choice for treating patients with capillariasis is mebendazole, 200 mg 2×/day for 20–30 days. An alternative treatment is albendazole, 400 mg 1×/day for 10 days (7,8). Variations in the treatment regimen used for patients with capillariasis at the study site suggest a need to train health professionals on the diagnosis, treatment, and follow-up of cases, and on disease prevention and control. Guidelines on proper laboratory techniques for diagnosis of capillariasis; treatment protocols and supportive measures; and protocols for detection, follow-up, and treatment for relapse cases must be developed. Rates of infection with protozoans and soil-transmitted helminths at the study site are high, which indicate fecal contamination of food and water. A review of records from the Katipunan rural health unit indicated that 76% of households in this municipality have access to toilets. Only 11% of households have water connections (level III). Fifty-seven percent of households have access to communal faucets (level II), and 31% have access only to rivers or springs (9). Therefore, increased access to toilets and safe water is needed. Local ordinances concerning ownership and use of toilets must be strictly enforced, and evaluation and rehabilitation of existing toilet and water systems must be conducted. In spite of efforts concerning information, education, and communication on capillariasis, many residents continue to eat raw or poorly cooked freshwater fish. Concurrent infection among household members, including those in younger age groups, was observed in this study. These findings result from the fact that consumption of kinilaw has become widely accepted and is consumed as a viand (choice food) by families. Thus, information, education, and communication campaigns must be intensified. A promising approach is through collaboration with other agencies. For example, the Department of Education in the Philippines may become involved in dissemination of information on capillariasis to students and in early detection and treatment of infected school children.

Fluid Inclusion Microthermometry and Implications for the Mechanisms of Ore‐Grade Gold Mineralization in Epithermal System, Lalab Orebody, Sibutad, Zamboanga del Norte, Philippines

AbstractThe Sibutad gold deposit has gold associated in quartz veins. The most important of these is the Lalab orebody, which contains ore‐grade gold, predominantly, in milky quartz veins and veinlets. Here, alteration quartz and fine‐grained crystalline clear and milky quartz were formed from hydrothermal fluids in three stages, namely stages I, II and III. Fluid inclusion microthermometry was carried out on stage I milky quartz, stage II fine‐grained alteration quartz and stage III milky quartz ± barite veins and veinlets. Homogenization temperatures (TH) are >248°C in stage I, 214–232°C in stage II and 186–239°C in stage III. These fluid inclusions have salinity between 1 and 2 wt% NaCl equivalent. In terms of gold assay, stage I drill‐core samples have gold grades 0.53–0.76 g/ton Au, stage II samples have 1.12–3.70 g/ton Au and stage III samples have 9.06–23.88 g/ton Au. This correlation suggests that gold was precipitated from the stage II and III fluids.

Mass Change Calculations as Applied to the Search for Volcanogenic Massive Sulfide Deposits: An Example from Malusok, Siocon, Zamboanga del Norte, Mindanao, Philippines

Abstract. The Malusok volcanogenic massive sulfide (VMS) deposits comprise two adjacent ore bodies, the Main Malusok and the Malusok Southeast ore bodies, hosted within Cretaceous metamorphic rocks. Owing to the structural and metamor-phic overprinting combined with intense hydrothermal alteration, primary textures of the Malusok volcanic rocks have been obliterated. The stratigraphic correlation of the Main Malusok and the Malusok Southeast ore bodies show that both deposits are essentially confined within a single stratigraphic interval. The lithogeochemical analysis of the Malusok samples shows that constituent lithologies have precursor compositions ranging from sub-alkaline basalts to rhyodacites. Field and mass flux data suggest that the Main Malusok VMS deposits were derived as a consequence of axial hydrothermal activity. The Malusok Southeast ore bodies represent satellite deposits generated by off-axis hydrothermal activities from vents aligned along a NW-SE trend with the Main Malusok zone. This alignment represents an ancient fissure that served as a pathway for the upwelling metalliferous hydrothermal fluids. In searching for lateral extensions of these VMS deposits, this NW-SE alignment should serve as a possible exploration guide.

Geology and volcanic stratigraphy of the Canatuan and Malusok volcanogenic massive sulfide deposits, southwestern Mindanao, Philippines

The Canatuan and Malusok massive sulfide deposits are located near Siocon, Zamboanga del Norte, in southwestern Mindanao, Philippines. The Canatuan–Malusok area is underlain by the Jurassic–Cretaceous Tungauan schists, which form much of the Zamboanga Peninsula. The volcanic strata at Canatuan and Malusok can be traced for >7 km along strike and is host to at least three discrete massive sulfide bodies: Canatuan, Malusok and SE Malusok. Basal basaltic andesite volcanic rocks are generally chemically uniform and show only moderate alteration. The massive sulfide deposits occur in overlying rhyolitic to rhyodacitic volcanic rocks that are altered to a schistose assemblage of quartz, sericite, chlorite and pyrite. The alteration is texturally destructive but graded clastic beds are locally observed. Despite tropical saprolitic weathering, four lithogeochemical subunits of the felsic package are identified. Stratigraphic interleaving, however, has made correlation of these units over any significant distance difficult. The sulfide lenses are overlain by a few metres of felsic schists which locally contain manganese-bearing silicates and oxides that serve as a stratigraphic marker. Hangingwall andesitic volcaniclastic rocks are discontinuously preserved, although where present, they consist of regularly bedded mafic volcanic sandstones. The lateral continuity of a manganese-bearing marker and flanking felsic volcaniclastic intervals indicate that locally the volcanic strata form a homoclinal sequence. The Canatuan Au–Ag–Cu–Zn deposit consists of a gossan overlying a massive sulfide lens. The sulfides and gossan are flat lying and hosted within felsic volcanic rocks. The gossan is gold–silver-rich, and was formed by a combination of oxidation and volume collapse of the original sulfide lens. The sulfide minerals present below the current water table, are auriferous massive pyrite with base metal sulfides, with some supergene chalcocite. The transition from gossan to sulfides is very sharp, occurring at the water table. Massive sulfide deposits at Malusok are hosted in the same felsic sequence as Canatuan and they have similar base and precious metal contents. Only limited gossan has been found at Malusok. The bimodal nature of the volcanic rocks at Canatuan, together with their low HFSE contents, near-flat REE patterns and tholeiitic affinities, suggest that they formed in an intra-oceanic arc setting above a depleted mantle source. Mafic and felsic volcanic rocks of similar composition have been recovered from the Tonga-Kermadec and Izu-Bonin-Marianas island-arc systems in the western Pacific. Mafic rocks at Canatuan show no evidence for LILE enrichment that characterizes melts derived from metasomatized mantle under more mature arcs, suggesting that they are the product of a nascent, rather than a mature arc. There is no evidence from the REE, or other incompatible trace elements, that continental crust or evolved arc crust was involved in the generation of the Canatuan-Malusok volcanic rocks. Although it has been proposed that the Zamboanga metamorphic complex comprises microcontinental fragments of Eurasian affinity, our data do not support an evolved crustal setting for the Canatuan-Malusok volcanic rocks, which we suggest were derived from an intra-oceanic arc and subsequently accreted to the eastern Mindanao terrane.

Gold and Base-Metal Sulfide Mineralogy and Paragenesis of the Lalab Orebody, Sibutad, Zamboanga del Norte, Philippines: Clues to the Fluid Composition and Formation of Gold-Rich Zones

The Sibutad gold deposit is one of the precious and base-metal deposits in the northeastern portion of the Zamboanga Peninsula, Mindanao island, the Philippines. The host rocks for gold-bearing quartz veins and disseminated to vein-associated base-metal sulfides are the andesite flows of the lower member Malindang Volcanics. In the Lalab orebody, these andesite flows vary from aphanitic to porpyhritic. Gold and base-metal sulfides, such as sphalerite ± galena, chalcopyrite, and bornite, occur in the variably altered andesite and hydrothermal breccia bodies. Clast type, alteration overprint, and cross-cutting relationships indicate the occurrence of three stages of hydrothermal activities, namely pre-breccia wallrock alteration, post-breccia wallrock alteration, and gold mineralization. Pre-breccia wallrock alteration occurred during Stage I. Post-breccia altered wallrocks and milky quartz veins and veinlets are characterized by marginal grade gold mineralization, with assays from 0.5 to 1.0 g/ton Au, and ore grade, with >1.0 g/ton Au, rocks, respectively. Post-breccia wallrock alteration refers to Stage II and formation of ore-grade-bearing milky quartz veins and veinlets are grouped in Stage III. Stage I is characterized by the assemblage of pyrite-sphalerite ± galena-chalcopyrite-bornitehematite. Stage II is represented by pyrite-chalcopyrite-bornite ± sphalerite ± gold-hematite. Stage III shows pyrite-bornite-chalcopyrite-gold-hematite assemblage. Sphalerite content decreases from Stage I through Stage II until Stage III. Bornite content increases and gold forms from Stage I and Stage II to Stage III. The occurrence of ore-grade gold zones in the central (100 m to 200 m above sea level) and deeper (50 m below sea level to 100 m above sea level) portions of the Lalab orebody are evidenced by the distribution of milky quartz veins. Gold-rich zones occur in Stage III milky quartz veins and veinlets in specific horizons within Stage II altered wallrocks. The Stage III milky quartz veins and veinlets were the most favorable for the precipitation of gold. The dominant metal ligand in the mineralizing solution apparently changed from chloride in Stage I to bi-sulfide during stages II and III. The prolific gold-bearing Stage III hydrothermal solution, with bi-sulfide as the dominant gold carrier, has precipitated its gold in favorable depositional settings as dictated by increased permeability, pervasive silicification, and depth-temperature condition.

Shallow to near-surface, vein-type epithermal gold mineralization at Lalab in the Sibutad gold deposit, Zamboanga del Norte, Mindanao, Philippines

The Sibutad vein-type epithermal gold deposit is the most promising economically feasible gold mineralization found in recent years in Zamboanga del Norte province in Zamboanga Peninsula, Mindanao island. The Sibutad gold deposit occurs in Pliocene to Pleistocene volcanic rocks, resting on a deformed island arc block to the east of the tectonically active Sindangan–Cotabato–Daguma Lineament. The host rocks are the Malindang Volcanics, composed of lower and upper members, which are both intruded by andesite porphyry. The lower member is made up of andesite flows, dacite tuff and tuffite, whereas volcanic breccia and tuff breccia characterize the upper member. The Sibutad gold deposit is subdivided into the Larayan and Lalab prospects. In Lalab, which is the prospect studied, hydrothermal activity and gold mineralization occur in the andesite flows. The geology, alteration and mineralization of the Lalab orebody are of adularia-sericite type that suggests the gold was precipitated from reduced, near-neutral pH solutions within a shallow to near-surface environment. The following events produced the Lalab orebody: (1) pre-breccia wallrock alteration, (2) hydrothermal brecciation, (3) post-breccia wallrock alteration, and (4) gold mineralization. Gold precipitated in quartz veins was a response to boiling, followed by fluid mixing. Prolific gold zones occur between 30 m below sea level and 200 m above sea level.

Stratigraphic Correlation of the Malusok Volcanogenic Massive Sulfide Deposits, Southern Mindanao, Philippines

Abstract: Two adjacent volcanogenic massive sulfide (VMS) deposits, the Main Malusok and the Malusok Southeast, are delineated within Barangay Tabayo, Siocon, Zamboanga del Norte, Mindanao, Philippines. These deposits comprise massive to semi‐massive sulfide lenses representing the down‐dip equivalent of oxidized gossans. The massive sulfides have a primary mineral assemblage of pyrite‐chalcopyrite‐sphalerite with significant amounts of supergene copper in the form of chal‐cocite. Owing to structural and metamorphic overprinting combined with intense alteration, primary textures are generally obliterated. Rock types are classified according to dominant mineral assemblages whereas the main lithologic units comprising the Malusok volcanic package are divided based on the position of each unit relative to the mineralized zone. The main lithologic units are designated as the hanging wall, the host, and the footwall sequences. In correlating the stratigraphy of the Main Malusok zone with that of the Malusok Southeast zone, a chlorite/epidote‐rich interval located at the base of the hanging wall sequence serves as a distinct stratigraphic marker from which all lithologies are referred to. Comparisons between the stratigraphy of the two areas show that massive to semi‐massive sulfide lenses are confined within a single stratigraphic interval representing the favorable horizon for the entire Malusok area. However, differences exist relative to style of mineralization and configuration of the altered interval between the Main Malusok and the Malusok Southeast VMS deposits. Based on characteristics exhibited by each individual deposit, it is inferred that the Main Malusok VMS deposit overlies a feeder zone whereas the Malusok Southeast sulfide lenses represent satellite deposits and transported blocks.