Phan Idn cac bieu hien khoang hoa molybden tap trung d ddi Fansipan va d phan phia Nam Trung Bd, Da Lat, Chau Ddc... lien quan vdi cac xam nhap granitoid Mezozoi mupn - Kainozoi. Cac diem quang Sa Pa va Niii Sam (Chau Ddc) la diln hinh cho kieu quang nay. Cac mach quang dudi dang mach thach anh - fenspat - molybdenit xuyen c4t
qua cac da xam nhap granit. Thdnh phdn khoang vat chu yiu la molybdenh, chalcopyrit,
pyrit vdi tap hgp khoang vat bismut: bismutin, bismut tu sinh, galenobismut, cosalit.
Quang c6 cdu tao mach, xam tan vdi kien true hat tu hinh, tha hinh, v^y, t4m chii cd.
(Anh 58, 59, 60).
Quang cd ngudn gdc nhiet dich nhiet dp cao.
IIL Nhom cac nguyen to litophil: Sn-W
3.1. Kieu quang casiterit - wolframit - thach anh
La mpt trong nhirng kieu quang thiec chii yeu cd quy mo trii lugng dang ke va la ngudn cung cap casiterit chinh cho cac mo sa khoang. Da biet cac md quang d cac viing TTnh Tiic, Thien Ke, Da Lien (Tam Dao), Bu Me (Thudng Xuan), Ba Na (Quang Nam)...
Than quang cd dang mach, mach phan nhanh, budu, d. Thdnh phdn khoang vat quang
chii yeu la casiterit, wolframit, thii yeu co arsenopyrit, pyrit, pyrotin, chalcopyrit,
sphalerit, galenit, molybdenit, rutil, sheelit, bismutin, stanin... Cdu tao quang thudng pho biin dang mach, xam tan vdi kiin true hat tu hinh dang tam, ca nat, vi mach, nhii tuong -
tach dung dich cung. (Anh 61, 62, 63)
Quang thupc ngudn goc khi hoa nhiet dich nhiet dp cao.
3.2. Kieu quang casiterit - silicat - sulfur
Cac md thuoc kilu quang nay gap d vung Tam Dao, Quy Hgp. Cac than quang c6
dang mach vdi kich thudc khac nhau hoac dang d, thau kinh, budu. Khoang vat quang
chu yiu la casiterit, arsenopyrit, pyrotin, pyrit, thu ylu bismutin, galenobismut, bismut tu
sinh, cosalit, galenit, sphalerit... Khoang vat mach chii yeu gdm thach anh, turmalin,
biotit... Cdu tao quang chii ylu dang mach, vi mach, xam tan vdi kien true hat tu hinh ca
nat, vi mang mach xen lap (Anh 64, 65, 66, 67). Quang CO ngudn gdc nhiet dich.
Anh 57. Cinaba giua tap hgp canxit. Sb - Hg Yen Ve. DPD 37x. Nicon (-)
Anh 59. Molybdenit vdi kiln true vay. Mo Hon San (Nha Trang). DPD 75x. Nicon (-)
Anh 61. Mach Casiterit - thach anh. Sn Tam Dao. Mau cue
y*f-
\ \
Anh 63. Chalcopyrit xuyen lap trong tap hgp casiterit bi ea nat. Sn-W PiaoSc. DPD 75x. Nicon (-)
Anh 64. Arsenopyrit bi ca nat, scorodit hoa giiia cac tap hop casiterit nira tir hinh. Sn Tam Dao. DPD 75x. Nicon (-)
Anh 65. Chalcopyrit dang vi mach xuyen idp theo dudng nut eua tap hgp casiterit. Sn Tam Dao. DPD 75x. Nicon (-)
Anh 66. Arsenopyrit bj scorodit hoan toan bao quanh cac hat casiterit nua tu hinh. Sn Quy Hgp. DPD 37x. Nicon (-)
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