FANDOM


Mankayan Dacitic Complex    

Lithology

Dacite, breccias, pyroclastic rocks

Stratigraphic relations

Intrudes older rocks

Distribution

Lepanto mine, Mankayan, Benguet; Baguio District

Age

Late Pliocene - Pleistocene

Previous Name   

Imbaguila / BatoDacite Porphyry

Named by

Lepanto Consolidated Mining Company

Renamed by

Balce and others (1980)

Synonymy

Balatoc Dacite

Dacitic rock units are represented by dacite porphyries in the Lepanto mine, Mankayan, Benguet and the Balatoc Dacite Plug in the Baguio District.  Dacite domes, diatremebreccias and pyroclastics in the Lepanto area preceded and post-dated epithermal mineralization.  These are known locally as Imbaguila Dacite Porphyry, and Bato Dacite Porphyryand their pyroclastic equivalents.  The Imbaguila predates mineralization while the Bato postdates the mineralization.

The plug at the Balatoc Mine is roughly a vertical pipe measuring 980 m by 730 m in plan and tapers downward to a maximum known depth of 2,000 m (Mitchell and Leach, 1991).  The pipe contains blocks of various rock types that include quartz diorite, andesite, metasediments, dacite and granodiorite.  The matrix is made up of dacitic and andesitic material as well as an admixture of quartz, plagioclase and clayey material.  Gold-bearing veins traverse the breccia.  Later andesite dikes also cut across the breccia.

A similar type of breccia pipe is present in the Sto. Niño Mine.  According to Balce (1978), it is 1,200 m by 500 m in plan and the bulk of the pipe is dacitic in composition.

Wolfe (1981) gives a K/Ar date of 1.7 Ma for a sample of dacite.  Maleterre (1989) reports K/Ar dating of 1.5 Ma and 1.9 Ma for samples of dacite.  MMAJ-JICA (1983) gives a dating of 0.8 Ma for the Balatoc Plug.  These datings are equivalent to Pleistocene.  In Lepanto, K/Ar dating of biiotite from the earlier dacite gave a value of 2.9 ± 0.4 Ma (Sillitoe and Angeles, 1985).  On the other hand, K/Ardatings reported by Arribas and others (1994) for the later dacites (0.96 ± 0.29 Ma; 1.18 ± 0.08 Ma) are close to the dating for the Balatoc Plug (0.8 Ma).

Formation sequenceEdit

Ad blocker interference detected!


Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.