14.11.2013 Views

Overview of Results from the Greenstone ... - Geology Ontario

Overview of Results from the Greenstone ... - Geology Ontario

Overview of Results from the Greenstone ... - Geology Ontario

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Table 7. Diagnostic mineral assemblages (point data) are <strong>the</strong> basis for <strong>the</strong> definition <strong>of</strong> metamorphic grade in each metamorphic zone. Metamorphic zones (see also Thompson<br />

2005, Figure 2, back pocket) are derived <strong>from</strong> <strong>the</strong> grade in one or more rock associations. The first digit <strong>of</strong> <strong>the</strong> two-digit number in each cell indicates <strong>the</strong> rock association. The<br />

second digit indicates <strong>the</strong> relative metamorphic grade for <strong>the</strong> rock association (higher number, higher grade). The relative positions <strong>of</strong> <strong>the</strong> boundaries in rock associations 2 to 7<br />

that correspond approximately to <strong>the</strong> lower/upper greenschist zone boundary on <strong>the</strong> map are inferred. The precise positions <strong>of</strong> <strong>the</strong>se boundaries relative to each o<strong>the</strong>r have yet to<br />

be calibrated. Mineral name abbreviations: ab - albite, act - actinolite, am – amphibole undifferentiated, and - andalusite, bt - biotite, cb – carbonate (ankerite, calcite, dolomite,<br />

magnesite, siderite), cht - chlorite, crd - cordierite, ctd - chloritoid, cum - cummingtonite, diop - diopside, epg - epidote group, grt - garnet, gru - grünerite,<br />

hn - hornblende, kf - potassium-feldspar, mt - magnetite, plg - plagioclase, se - serpentine, sil - sillimanite, st - staurolite, tlc - talc, trm - tremolite, wm - white mica (muscovite,<br />

paragonite, talc).<br />

Metamorphic Grade<br />

Rock Association<br />

1) Metabasites: metabasalt/gabbro/diabase,<br />

greenstone, amphibolite, meta-andesite<br />

2) Metaquartz<strong>of</strong>eldspathic rocks:<br />

metarhyolite/dacite, qtz-fp metaporphyry,<br />

felsic metavolcaniclastite, metawacke<br />

3) Metamorphosed ultramafic rocks:<br />

metakomatiite, metaperidotite/dunite<br />

4) Metamorphosed aluminum-rich rocks:<br />

metashale/siltstone, metahydro<strong>the</strong>rmal<br />

alteration<br />

5) Chemical metasedimentary rocks,<br />

meta-iron formation<br />

6) Metamorphosed granitoids:<br />

metagranite to metatonalite<br />

7) Metamophosed carbonate-rich rocks:<br />

carbonate metasediments, meta-interpillow<br />

rock, metahydro<strong>the</strong>rmal alteration, cht-cb<br />

schist<br />

8) Unmetamorphosed granitoids:<br />

granite to tonalite<br />

Sub-greenschist<br />

Facies<br />

Subgreenschist<br />

Zone<br />

Lower Greenschist<br />

Zone<br />

Greenschist Facies Amphibolite Facies<br />

Metamorphic Zones on Map<br />

Upper Greenschist<br />

Zone<br />

Transition<br />

Zone<br />

Diagnostic Mineral Assemblages<br />

10 prn, prn-pu 11 act-cht-epg-ab 12 act-hn 13 hn-plg(calcic)<br />

20 prn, prn-pu<br />

cht-wm<br />

30<br />

21 cht-wm cht-kf<br />

cht-wm-cb<br />

31 cht-tlc-cb, se-cht<br />

cht-tlc-se-cb<br />

22 bt<br />

epg-act<br />

32 clinoamphibole (trm, cum)<br />

40 41 cht-wm 42 bt, bt-grt, ctd-cht<br />

50 minesotaite<br />

greenalite<br />

51 qtz-cht, cht-cb,<br />

mt-qtz<br />

23 bt-hn<br />

52 clinoamphibole (cum/gru), am-grt, two am<br />

60 prn, prn-pu 61 cht-kf, cht-wm 62 bt, bt-epg, bt-epg-am<br />

70<br />

71 cht-cb-qtz<br />

cht-cb-wm-qtz<br />

72 bt-cht-cb<br />

epg-cht-am-cb<br />

80 no metamorphic minerals<br />

Amphibolite Zone<br />

43 crd-and/sil-bt<br />

st-and/sil-bt, crd orthoamphibole<br />

73 diop-am-grt, hn-bt-qtz<br />

76

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!